/* Predictive commoning. Copyright (C) 2005-2020 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see . */ /* This file implements the predictive commoning optimization. Predictive commoning can be viewed as CSE around a loop, and with some improvements, as generalized strength reduction-- i.e., reusing values computed in earlier iterations of a loop in the later ones. So far, the pass only handles the most useful case, that is, reusing values of memory references. If you think this is all just a special case of PRE, you are sort of right; however, concentrating on loops is simpler, and makes it possible to incorporate data dependence analysis to detect the opportunities, perform loop unrolling to avoid copies together with renaming immediately, and if needed, we could also take register pressure into account. Let us demonstrate what is done on an example: for (i = 0; i < 100; i++) { a[i+2] = a[i] + a[i+1]; b[10] = b[10] + i; c[i] = c[99 - i]; d[i] = d[i + 1]; } 1) We find data references in the loop, and split them to mutually independent groups (i.e., we find components of a data dependence graph). We ignore read-read dependences whose distance is not constant. (TODO -- we could also ignore antidependences). In this example, we find the following groups: a[i]{read}, a[i+1]{read}, a[i+2]{write} b[10]{read}, b[10]{write} c[99 - i]{read}, c[i]{write} d[i + 1]{read}, d[i]{write} 2) Inside each of the group, we verify several conditions: a) all the references must differ in indices only, and the indices must all have the same step b) the references must dominate loop latch (and thus, they must be ordered by dominance relation). c) the distance of the indices must be a small multiple of the step We are then able to compute the difference of the references (# of iterations before they point to the same place as the first of them). Also, in case there are writes in the loop, we split the groups into chains whose head is the write whose values are used by the reads in the same chain. The chains are then processed independently, making the further transformations simpler. Also, the shorter chains need the same number of registers, but may require lower unrolling factor in order to get rid of the copies on the loop latch. In our example, we get the following chains (the chain for c is invalid). a[i]{read,+0}, a[i+1]{read,-1}, a[i+2]{write,-2} b[10]{read,+0}, b[10]{write,+0} d[i + 1]{read,+0}, d[i]{write,+1} 3) For each read, we determine the read or write whose value it reuses, together with the distance of this reuse. I.e. we take the last reference before it with distance 0, or the last of the references with the smallest positive distance to the read. Then, we remove the references that are not used in any of these chains, discard the empty groups, and propagate all the links so that they point to the single root reference of the chain (adjusting their distance appropriately). Some extra care needs to be taken for references with step 0. In our example (the numbers indicate the distance of the reuse), a[i] --> (*) 2, a[i+1] --> (*) 1, a[i+2] (*) b[10] --> (*) 1, b[10] (*) 4) The chains are combined together if possible. If the corresponding elements of two chains are always combined together with the same operator, we remember just the result of this combination, instead of remembering the values separately. We may need to perform reassociation to enable combining, for example e[i] + f[i+1] + e[i+1] + f[i] can be reassociated as (e[i] + f[i]) + (e[i+1] + f[i+1]) and we can combine the chains for e and f into one chain. 5) For each root reference (end of the chain) R, let N be maximum distance of a reference reusing its value. Variables R0 up to RN are created, together with phi nodes that transfer values from R1 .. RN to R0 .. R(N-1). Initial values are loaded to R0..R(N-1) (in case not all references must necessarily be accessed and they may trap, we may fail here; TODO sometimes, the loads could be guarded by a check for the number of iterations). Values loaded/stored in roots are also copied to RN. Other reads are replaced with the appropriate variable Ri. Everything is put to SSA form. As a small improvement, if R0 is dead after the root (i.e., all uses of the value with the maximum distance dominate the root), we can avoid creating RN and use R0 instead of it. In our example, we get (only the parts concerning a and b are shown): for (i = 0; i < 100; i++) { f = phi (a[0], s); s = phi (a[1], f); x = phi (b[10], x); f = f + s; a[i+2] = f; x = x + i; b[10] = x; } 6) Factor F for unrolling is determined as the smallest common multiple of (N + 1) for each root reference (N for references for that we avoided creating RN). If F and the loop is small enough, loop is unrolled F times. The stores to RN (R0) in the copies of the loop body are periodically replaced with R0, R1, ... (R1, R2, ...), so that they can be coalesced and the copies can be eliminated. TODO -- copy propagation and other optimizations may change the live ranges of the temporary registers and prevent them from being coalesced; this may increase the register pressure. In our case, F = 2 and the (main loop of the) result is for (i = 0; i < ...; i += 2) { f = phi (a[0], f); s = phi (a[1], s); x = phi (b[10], x); f = f + s; a[i+2] = f; x = x + i; b[10] = x; s = s + f; a[i+3] = s; x = x + i; b[10] = x; } Apart from predictive commoning on Load-Load and Store-Load chains, we also support Store-Store chains -- stores killed by other store can be eliminated. Given below example: for (i = 0; i < n; i++) { a[i] = 1; a[i+2] = 2; } It can be replaced with: t0 = a[0]; t1 = a[1]; for (i = 0; i < n; i++) { a[i] = 1; t2 = 2; t0 = t1; t1 = t2; } a[n] = t0; a[n+1] = t1; If the loop runs more than 1 iterations, it can be further simplified into: for (i = 0; i < n; i++) { a[i] = 1; } a[n] = 2; a[n+1] = 2; The interesting part is this can be viewed either as general store motion or general dead store elimination in either intra/inter-iterations way. With trivial effort, we also support load inside Store-Store chains if the load is dominated by a store statement in the same iteration of loop. You can see this as a restricted Store-Mixed-Load-Store chain. TODO: For now, we don't support store-store chains in multi-exit loops. We force to not unroll in case of store-store chain even if other chains might ask for unroll. Predictive commoning can be generalized for arbitrary computations (not just memory loads), and also nontrivial transfer functions (e.g., replacing i * i with ii_last + 2 * i + 1), to generalize strength reduction. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "backend.h" #include "rtl.h" #include "tree.h" #include "gimple.h" #include "predict.h" #include "tree-pass.h" #include "ssa.h" #include "gimple-pretty-print.h" #include "alias.h" #include "fold-const.h" #include "cfgloop.h" #include "tree-eh.h" #include "gimplify.h" #include "gimple-iterator.h" #include "gimplify-me.h" #include "tree-ssa-loop-ivopts.h" #include "tree-ssa-loop-manip.h" #include "tree-ssa-loop-niter.h" #include "tree-ssa-loop.h" #include "tree-into-ssa.h" #include "tree-dfa.h" #include "tree-ssa.h" #include "tree-data-ref.h" #include "tree-scalar-evolution.h" #include "tree-affine.h" #include "builtins.h" /* The maximum number of iterations between the considered memory references. */ #define MAX_DISTANCE (target_avail_regs < 16 ? 4 : 8) /* Data references (or phi nodes that carry data reference values across loop iterations). */ typedef class dref_d { public: /* The reference itself. */ struct data_reference *ref; /* The statement in that the reference appears. */ gimple *stmt; /* In case that STMT is a phi node, this field is set to the SSA name defined by it in replace_phis_by_defined_names (in order to avoid pointing to phi node that got reallocated in the meantime). */ tree name_defined_by_phi; /* Distance of the reference from the root of the chain (in number of iterations of the loop). */ unsigned distance; /* Number of iterations offset from the first reference in the component. */ widest_int offset; /* Number of the reference in a component, in dominance ordering. */ unsigned pos; /* True if the memory reference is always accessed when the loop is entered. */ unsigned always_accessed : 1; } *dref; /* Type of the chain of the references. */ enum chain_type { /* The addresses of the references in the chain are constant. */ CT_INVARIANT, /* There are only loads in the chain. */ CT_LOAD, /* Root of the chain is store, the rest are loads. */ CT_STORE_LOAD, /* There are only stores in the chain. */ CT_STORE_STORE, /* A combination of two chains. */ CT_COMBINATION }; /* Chains of data references. */ typedef struct chain { /* Type of the chain. */ enum chain_type type; /* For combination chains, the operator and the two chains that are combined, and the type of the result. */ enum tree_code op; tree rslt_type; struct chain *ch1, *ch2; /* The references in the chain. */ vec refs; /* The maximum distance of the reference in the chain from the root. */ unsigned length; /* The variables used to copy the value throughout iterations. */ vec vars; /* Initializers for the variables. */ vec inits; /* Finalizers for the eliminated stores. */ vec finis; /* gimple stmts intializing the initial variables of the chain. */ gimple_seq init_seq; /* gimple stmts finalizing the eliminated stores of the chain. */ gimple_seq fini_seq; /* True if there is a use of a variable with the maximal distance that comes after the root in the loop. */ unsigned has_max_use_after : 1; /* True if all the memory references in the chain are always accessed. */ unsigned all_always_accessed : 1; /* True if this chain was combined together with some other chain. */ unsigned combined : 1; /* True if this is store elimination chain and eliminated stores store loop invariant value into memory. */ unsigned inv_store_elimination : 1; } *chain_p; /* Describes the knowledge about the step of the memory references in the component. */ enum ref_step_type { /* The step is zero. */ RS_INVARIANT, /* The step is nonzero. */ RS_NONZERO, /* The step may or may not be nonzero. */ RS_ANY }; /* Components of the data dependence graph. */ struct component { /* The references in the component. */ vec refs; /* What we know about the step of the references in the component. */ enum ref_step_type comp_step; /* True if all references in component are stores and we try to do intra/inter loop iteration dead store elimination. */ bool eliminate_store_p; /* Next component in the list. */ struct component *next; }; /* Bitmap of ssa names defined by looparound phi nodes covered by chains. */ static bitmap looparound_phis; /* Cache used by tree_to_aff_combination_expand. */ static hash_map *name_expansions; /* Dumps data reference REF to FILE. */ extern void dump_dref (FILE *, dref); void dump_dref (FILE *file, dref ref) { if (ref->ref) { fprintf (file, " "); print_generic_expr (file, DR_REF (ref->ref), TDF_SLIM); fprintf (file, " (id %u%s)\n", ref->pos, DR_IS_READ (ref->ref) ? "" : ", write"); fprintf (file, " offset "); print_decs (ref->offset, file); fprintf (file, "\n"); fprintf (file, " distance %u\n", ref->distance); } else { if (gimple_code (ref->stmt) == GIMPLE_PHI) fprintf (file, " looparound ref\n"); else fprintf (file, " combination ref\n"); fprintf (file, " in statement "); print_gimple_stmt (file, ref->stmt, 0, TDF_SLIM); fprintf (file, "\n"); fprintf (file, " distance %u\n", ref->distance); } } /* Dumps CHAIN to FILE. */ extern void dump_chain (FILE *, chain_p); void dump_chain (FILE *file, chain_p chain) { dref a; const char *chain_type; unsigned i; tree var; switch (chain->type) { case CT_INVARIANT: chain_type = "Load motion"; break; case CT_LOAD: chain_type = "Loads-only"; break; case CT_STORE_LOAD: chain_type = "Store-loads"; break; case CT_STORE_STORE: chain_type = "Store-stores"; break; case CT_COMBINATION: chain_type = "Combination"; break; default: gcc_unreachable (); } fprintf (file, "%s chain %p%s\n", chain_type, (void *) chain, chain->combined ? " (combined)" : ""); if (chain->type != CT_INVARIANT) fprintf (file, " max distance %u%s\n", chain->length, chain->has_max_use_after ? "" : ", may reuse first"); if (chain->type == CT_COMBINATION) { fprintf (file, " equal to %p %s %p in type ", (void *) chain->ch1, op_symbol_code (chain->op), (void *) chain->ch2); print_generic_expr (file, chain->rslt_type, TDF_SLIM); fprintf (file, "\n"); } if (chain->vars.exists ()) { fprintf (file, " vars"); FOR_EACH_VEC_ELT (chain->vars, i, var) { fprintf (file, " "); print_generic_expr (file, var, TDF_SLIM); } fprintf (file, "\n"); } if (chain->inits.exists ()) { fprintf (file, " inits"); FOR_EACH_VEC_ELT (chain->inits, i, var) { fprintf (file, " "); print_generic_expr (file, var, TDF_SLIM); } fprintf (file, "\n"); } fprintf (file, " references:\n"); FOR_EACH_VEC_ELT (chain->refs, i, a) dump_dref (file, a); fprintf (file, "\n"); } /* Dumps CHAINS to FILE. */ extern void dump_chains (FILE *, vec ); void dump_chains (FILE *file, vec chains) { chain_p chain; unsigned i; FOR_EACH_VEC_ELT (chains, i, chain) dump_chain (file, chain); } /* Dumps COMP to FILE. */ extern void dump_component (FILE *, struct component *); void dump_component (FILE *file, struct component *comp) { dref a; unsigned i; fprintf (file, "Component%s:\n", comp->comp_step == RS_INVARIANT ? " (invariant)" : ""); FOR_EACH_VEC_ELT (comp->refs, i, a) dump_dref (file, a); fprintf (file, "\n"); } /* Dumps COMPS to FILE. */ extern void dump_components (FILE *, struct component *); void dump_components (FILE *file, struct component *comps) { struct component *comp; for (comp = comps; comp; comp = comp->next) dump_component (file, comp); } /* Frees a chain CHAIN. */ static void release_chain (chain_p chain) { dref ref; unsigned i; if (chain == NULL) return; FOR_EACH_VEC_ELT (chain->refs, i, ref) free (ref); chain->refs.release (); chain->vars.release (); chain->inits.release (); if (chain->init_seq) gimple_seq_discard (chain->init_seq); chain->finis.release (); if (chain->fini_seq) gimple_seq_discard (chain->fini_seq); free (chain); } /* Frees CHAINS. */ static void release_chains (vec chains) { unsigned i; chain_p chain; FOR_EACH_VEC_ELT (chains, i, chain) release_chain (chain); chains.release (); } /* Frees a component COMP. */ static void release_component (struct component *comp) { comp->refs.release (); free (comp); } /* Frees list of components COMPS. */ static void release_components (struct component *comps) { struct component *act, *next; for (act = comps; act; act = next) { next = act->next; release_component (act); } } /* Finds a root of tree given by FATHERS containing A, and performs path shortening. */ static unsigned component_of (unsigned fathers[], unsigned a) { unsigned root, n; for (root = a; root != fathers[root]; root = fathers[root]) continue; for (; a != root; a = n) { n = fathers[a]; fathers[a] = root; } return root; } /* Join operation for DFU. FATHERS gives the tree, SIZES are sizes of the components, A and B are components to merge. */ static void merge_comps (unsigned fathers[], unsigned sizes[], unsigned a, unsigned b) { unsigned ca = component_of (fathers, a); unsigned cb = component_of (fathers, b); if (ca == cb) return; if (sizes[ca] < sizes[cb]) { sizes[cb] += sizes[ca]; fathers[ca] = cb; } else { sizes[ca] += sizes[cb]; fathers[cb] = ca; } } /* Returns true if A is a reference that is suitable for predictive commoning in the innermost loop that contains it. REF_STEP is set according to the step of the reference A. */ static bool suitable_reference_p (struct data_reference *a, enum ref_step_type *ref_step) { tree ref = DR_REF (a), step = DR_STEP (a); if (!step || TREE_THIS_VOLATILE (ref) || !is_gimple_reg_type (TREE_TYPE (ref)) || tree_could_throw_p (ref)) return false; if (integer_zerop (step)) *ref_step = RS_INVARIANT; else if (integer_nonzerop (step)) *ref_step = RS_NONZERO; else *ref_step = RS_ANY; return true; } /* Stores DR_OFFSET (DR) + DR_INIT (DR) to OFFSET. */ static void aff_combination_dr_offset (struct data_reference *dr, aff_tree *offset) { tree type = TREE_TYPE (DR_OFFSET (dr)); aff_tree delta; tree_to_aff_combination_expand (DR_OFFSET (dr), type, offset, &name_expansions); aff_combination_const (&delta, type, wi::to_poly_widest (DR_INIT (dr))); aff_combination_add (offset, &delta); } /* Determines number of iterations of the innermost enclosing loop before B refers to exactly the same location as A and stores it to OFF. If A and B do not have the same step, they never meet, or anything else fails, returns false, otherwise returns true. Both A and B are assumed to satisfy suitable_reference_p. */ static bool determine_offset (struct data_reference *a, struct data_reference *b, poly_widest_int *off) { aff_tree diff, baseb, step; tree typea, typeb; /* Check that both the references access the location in the same type. */ typea = TREE_TYPE (DR_REF (a)); typeb = TREE_TYPE (DR_REF (b)); if (!useless_type_conversion_p (typeb, typea)) return false; /* Check whether the base address and the step of both references is the same. */ if (!operand_equal_p (DR_STEP (a), DR_STEP (b), 0) || !operand_equal_p (DR_BASE_ADDRESS (a), DR_BASE_ADDRESS (b), 0)) return false; if (integer_zerop (DR_STEP (a))) { /* If the references have loop invariant address, check that they access exactly the same location. */ *off = 0; return (operand_equal_p (DR_OFFSET (a), DR_OFFSET (b), 0) && operand_equal_p (DR_INIT (a), DR_INIT (b), 0)); } /* Compare the offsets of the addresses, and check whether the difference is a multiple of step. */ aff_combination_dr_offset (a, &diff); aff_combination_dr_offset (b, &baseb); aff_combination_scale (&baseb, -1); aff_combination_add (&diff, &baseb); tree_to_aff_combination_expand (DR_STEP (a), TREE_TYPE (DR_STEP (a)), &step, &name_expansions); return aff_combination_constant_multiple_p (&diff, &step, off); } /* Returns the last basic block in LOOP for that we are sure that it is executed whenever the loop is entered. */ static basic_block last_always_executed_block (class loop *loop) { unsigned i; vec exits = get_loop_exit_edges (loop); edge ex; basic_block last = loop->latch; FOR_EACH_VEC_ELT (exits, i, ex) last = nearest_common_dominator (CDI_DOMINATORS, last, ex->src); exits.release (); return last; } /* Splits dependence graph on DATAREFS described by DEPENDS to components. */ static struct component * split_data_refs_to_components (class loop *loop, vec datarefs, vec depends) { unsigned i, n = datarefs.length (); unsigned ca, ia, ib, bad; unsigned *comp_father = XNEWVEC (unsigned, n + 1); unsigned *comp_size = XNEWVEC (unsigned, n + 1); struct component **comps; struct data_reference *dr, *dra, *drb; struct data_dependence_relation *ddr; struct component *comp_list = NULL, *comp; dref dataref; /* Don't do store elimination if loop has multiple exit edges. */ bool eliminate_store_p = single_exit (loop) != NULL; basic_block last_always_executed = last_always_executed_block (loop); auto_bitmap no_store_store_comps; FOR_EACH_VEC_ELT (datarefs, i, dr) { if (!DR_REF (dr)) { /* A fake reference for call or asm_expr that may clobber memory; just fail. */ goto end; } /* predcom pass isn't prepared to handle calls with data references. */ if (is_gimple_call (DR_STMT (dr))) goto end; dr->aux = (void *) (size_t) i; comp_father[i] = i; comp_size[i] = 1; } /* A component reserved for the "bad" data references. */ comp_father[n] = n; comp_size[n] = 1; FOR_EACH_VEC_ELT (datarefs, i, dr) { enum ref_step_type dummy; if (!suitable_reference_p (dr, &dummy)) { ia = (unsigned) (size_t) dr->aux; merge_comps (comp_father, comp_size, n, ia); } } FOR_EACH_VEC_ELT (depends, i, ddr) { poly_widest_int dummy_off; if (DDR_ARE_DEPENDENT (ddr) == chrec_known) continue; dra = DDR_A (ddr); drb = DDR_B (ddr); /* Don't do store elimination if there is any unknown dependence for any store data reference. */ if ((DR_IS_WRITE (dra) || DR_IS_WRITE (drb)) && (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know || DDR_NUM_DIST_VECTS (ddr) == 0)) eliminate_store_p = false; ia = component_of (comp_father, (unsigned) (size_t) dra->aux); ib = component_of (comp_father, (unsigned) (size_t) drb->aux); if (ia == ib) continue; bad = component_of (comp_father, n); /* If both A and B are reads, we may ignore unsuitable dependences. */ if (DR_IS_READ (dra) && DR_IS_READ (drb)) { if (ia == bad || ib == bad || !determine_offset (dra, drb, &dummy_off)) continue; } /* If A is read and B write or vice versa and there is unsuitable dependence, instead of merging both components into a component that will certainly not pass suitable_component_p, just put the read into bad component, perhaps at least the write together with all the other data refs in it's component will be optimizable. */ else if (DR_IS_READ (dra) && ib != bad) { if (ia == bad) { bitmap_set_bit (no_store_store_comps, ib); continue; } else if (!determine_offset (dra, drb, &dummy_off)) { bitmap_set_bit (no_store_store_comps, ib); merge_comps (comp_father, comp_size, bad, ia); continue; } } else if (DR_IS_READ (drb) && ia != bad) { if (ib == bad) { bitmap_set_bit (no_store_store_comps, ia); continue; } else if (!determine_offset (dra, drb, &dummy_off)) { bitmap_set_bit (no_store_store_comps, ia); merge_comps (comp_father, comp_size, bad, ib); continue; } } else if (DR_IS_WRITE (dra) && DR_IS_WRITE (drb) && ia != bad && ib != bad && !determine_offset (dra, drb, &dummy_off)) { merge_comps (comp_father, comp_size, bad, ia); merge_comps (comp_father, comp_size, bad, ib); continue; } merge_comps (comp_father, comp_size, ia, ib); } if (eliminate_store_p) { tree niters = number_of_latch_executions (loop); /* Don't do store elimination if niters info is unknown because stores in the last iteration can't be eliminated and we need to recover it after loop. */ eliminate_store_p = (niters != NULL_TREE && niters != chrec_dont_know); } comps = XCNEWVEC (struct component *, n); bad = component_of (comp_father, n); FOR_EACH_VEC_ELT (datarefs, i, dr) { ia = (unsigned) (size_t) dr->aux; ca = component_of (comp_father, ia); if (ca == bad) continue; comp = comps[ca]; if (!comp) { comp = XCNEW (struct component); comp->refs.create (comp_size[ca]); comp->eliminate_store_p = eliminate_store_p; comps[ca] = comp; } dataref = XCNEW (class dref_d); dataref->ref = dr; dataref->stmt = DR_STMT (dr); dataref->offset = 0; dataref->distance = 0; dataref->always_accessed = dominated_by_p (CDI_DOMINATORS, last_always_executed, gimple_bb (dataref->stmt)); dataref->pos = comp->refs.length (); comp->refs.quick_push (dataref); } if (eliminate_store_p) { bitmap_iterator bi; EXECUTE_IF_SET_IN_BITMAP (no_store_store_comps, 0, ia, bi) { ca = component_of (comp_father, ia); if (ca != bad) comps[ca]->eliminate_store_p = false; } } for (i = 0; i < n; i++) { comp = comps[i]; if (comp) { comp->next = comp_list; comp_list = comp; } } free (comps); end: free (comp_father); free (comp_size); return comp_list; } /* Returns true if the component COMP satisfies the conditions described in 2) at the beginning of this file. LOOP is the current loop. */ static bool suitable_component_p (class loop *loop, struct component *comp) { unsigned i; dref a, first; basic_block ba, bp = loop->header; bool ok, has_write = false; FOR_EACH_VEC_ELT (comp->refs, i, a) { ba = gimple_bb (a->stmt); if (!just_once_each_iteration_p (loop, ba)) return false; gcc_assert (dominated_by_p (CDI_DOMINATORS, ba, bp)); bp = ba; if (DR_IS_WRITE (a->ref)) has_write = true; } first = comp->refs[0]; ok = suitable_reference_p (first->ref, &comp->comp_step); gcc_assert (ok); first->offset = 0; for (i = 1; comp->refs.iterate (i, &a); i++) { /* Polynomial offsets are no use, since we need to know the gap between iteration numbers at compile time. */ poly_widest_int offset; if (!determine_offset (first->ref, a->ref, &offset) || !offset.is_constant (&a->offset)) return false; enum ref_step_type a_step; gcc_checking_assert (suitable_reference_p (a->ref, &a_step) && a_step == comp->comp_step); } /* If there is a write inside the component, we must know whether the step is nonzero or not -- we would not otherwise be able to recognize whether the value accessed by reads comes from the OFFSET-th iteration or the previous one. */ if (has_write && comp->comp_step == RS_ANY) return false; return true; } /* Check the conditions on references inside each of components COMPS, and remove the unsuitable components from the list. The new list of components is returned. The conditions are described in 2) at the beginning of this file. LOOP is the current loop. */ static struct component * filter_suitable_components (class loop *loop, struct component *comps) { struct component **comp, *act; for (comp = &comps; *comp; ) { act = *comp; if (suitable_component_p (loop, act)) comp = &act->next; else { dref ref; unsigned i; *comp = act->next; FOR_EACH_VEC_ELT (act->refs, i, ref) free (ref); release_component (act); } } return comps; } /* Compares two drefs A and B by their offset and position. Callback for qsort. */ static int order_drefs (const void *a, const void *b) { const dref *const da = (const dref *) a; const dref *const db = (const dref *) b; int offcmp = wi::cmps ((*da)->offset, (*db)->offset); if (offcmp != 0) return offcmp; return (*da)->pos - (*db)->pos; } /* Compares two drefs A and B by their position. Callback for qsort. */ static int order_drefs_by_pos (const void *a, const void *b) { const dref *const da = (const dref *) a; const dref *const db = (const dref *) b; return (*da)->pos - (*db)->pos; } /* Returns root of the CHAIN. */ static inline dref get_chain_root (chain_p chain) { return chain->refs[0]; } /* Given CHAIN, returns the last write ref at DISTANCE, or NULL if it doesn't exist. */ static inline dref get_chain_last_write_at (chain_p chain, unsigned distance) { for (unsigned i = chain->refs.length (); i > 0; i--) if (DR_IS_WRITE (chain->refs[i - 1]->ref) && distance == chain->refs[i - 1]->distance) return chain->refs[i - 1]; return NULL; } /* Given CHAIN, returns the last write ref with the same distance before load at index LOAD_IDX, or NULL if it doesn't exist. */ static inline dref get_chain_last_write_before_load (chain_p chain, unsigned load_idx) { gcc_assert (load_idx < chain->refs.length ()); unsigned distance = chain->refs[load_idx]->distance; for (unsigned i = load_idx; i > 0; i--) if (DR_IS_WRITE (chain->refs[i - 1]->ref) && distance == chain->refs[i - 1]->distance) return chain->refs[i - 1]; return NULL; } /* Adds REF to the chain CHAIN. */ static void add_ref_to_chain (chain_p chain, dref ref) { dref root = get_chain_root (chain); gcc_assert (wi::les_p (root->offset, ref->offset)); widest_int dist = ref->offset - root->offset; gcc_assert (wi::fits_uhwi_p (dist)); chain->refs.safe_push (ref); ref->distance = dist.to_uhwi (); if (ref->distance >= chain->length) { chain->length = ref->distance; chain->has_max_use_after = false; } /* Promote this chain to CT_STORE_STORE if it has multiple stores. */ if (DR_IS_WRITE (ref->ref)) chain->type = CT_STORE_STORE; /* Don't set the flag for store-store chain since there is no use. */ if (chain->type != CT_STORE_STORE && ref->distance == chain->length && ref->pos > root->pos) chain->has_max_use_after = true; chain->all_always_accessed &= ref->always_accessed; } /* Returns the chain for invariant component COMP. */ static chain_p make_invariant_chain (struct component *comp) { chain_p chain = XCNEW (struct chain); unsigned i; dref ref; chain->type = CT_INVARIANT; chain->all_always_accessed = true; FOR_EACH_VEC_ELT (comp->refs, i, ref) { chain->refs.safe_push (ref); chain->all_always_accessed &= ref->always_accessed; } chain->inits = vNULL; chain->finis = vNULL; return chain; } /* Make a new chain of type TYPE rooted at REF. */ static chain_p make_rooted_chain (dref ref, enum chain_type type) { chain_p chain = XCNEW (struct chain); chain->type = type; chain->refs.safe_push (ref); chain->all_always_accessed = ref->always_accessed; ref->distance = 0; chain->inits = vNULL; chain->finis = vNULL; return chain; } /* Returns true if CHAIN is not trivial. */ static bool nontrivial_chain_p (chain_p chain) { return chain != NULL && chain->refs.length () > 1; } /* Returns the ssa name that contains the value of REF, or NULL_TREE if there is no such name. */ static tree name_for_ref (dref ref) { tree name; if (is_gimple_assign (ref->stmt)) { if (!ref->ref || DR_IS_READ (ref->ref)) name = gimple_assign_lhs (ref->stmt); else name = gimple_assign_rhs1 (ref->stmt); } else name = PHI_RESULT (ref->stmt); return (TREE_CODE (name) == SSA_NAME ? name : NULL_TREE); } /* Returns true if REF is a valid initializer for ROOT with given DISTANCE (in iterations of the innermost enclosing loop). */ static bool valid_initializer_p (struct data_reference *ref, unsigned distance, struct data_reference *root) { aff_tree diff, base, step; poly_widest_int off; /* Both REF and ROOT must be accessing the same object. */ if (!operand_equal_p (DR_BASE_ADDRESS (ref), DR_BASE_ADDRESS (root), 0)) return false; /* The initializer is defined outside of loop, hence its address must be invariant inside the loop. */ gcc_assert (integer_zerop (DR_STEP (ref))); /* If the address of the reference is invariant, initializer must access exactly the same location. */ if (integer_zerop (DR_STEP (root))) return (operand_equal_p (DR_OFFSET (ref), DR_OFFSET (root), 0) && operand_equal_p (DR_INIT (ref), DR_INIT (root), 0)); /* Verify that this index of REF is equal to the root's index at -DISTANCE-th iteration. */ aff_combination_dr_offset (root, &diff); aff_combination_dr_offset (ref, &base); aff_combination_scale (&base, -1); aff_combination_add (&diff, &base); tree_to_aff_combination_expand (DR_STEP (root), TREE_TYPE (DR_STEP (root)), &step, &name_expansions); if (!aff_combination_constant_multiple_p (&diff, &step, &off)) return false; if (maybe_ne (off, distance)) return false; return true; } /* Finds looparound phi node of LOOP that copies the value of REF, and if its initial value is correct (equal to initial value of REF shifted by one iteration), returns the phi node. Otherwise, NULL_TREE is returned. ROOT is the root of the current chain. */ static gphi * find_looparound_phi (class loop *loop, dref ref, dref root) { tree name, init, init_ref; gimple *init_stmt; edge latch = loop_latch_edge (loop); struct data_reference init_dr; gphi_iterator psi; if (is_gimple_assign (ref->stmt)) { if (DR_IS_READ (ref->ref)) name = gimple_assign_lhs (ref->stmt); else name = gimple_assign_rhs1 (ref->stmt); } else name = PHI_RESULT (ref->stmt); if (!name) return NULL; tree entry_vuse = NULL_TREE; gphi *phi = NULL; for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi)) { gphi *p = psi.phi (); if (PHI_ARG_DEF_FROM_EDGE (p, latch) == name) phi = p; else if (virtual_operand_p (gimple_phi_result (p))) entry_vuse = PHI_ARG_DEF_FROM_EDGE (p, loop_preheader_edge (loop)); if (phi && entry_vuse) break; } if (!phi || !entry_vuse) return NULL; init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop)); if (TREE_CODE (init) != SSA_NAME) return NULL; init_stmt = SSA_NAME_DEF_STMT (init); if (gimple_code (init_stmt) != GIMPLE_ASSIGN) return NULL; gcc_assert (gimple_assign_lhs (init_stmt) == init); init_ref = gimple_assign_rhs1 (init_stmt); if (!REFERENCE_CLASS_P (init_ref) && !DECL_P (init_ref)) return NULL; /* Analyze the behavior of INIT_REF with respect to LOOP (innermost loop enclosing PHI). */ memset (&init_dr, 0, sizeof (struct data_reference)); DR_REF (&init_dr) = init_ref; DR_STMT (&init_dr) = phi; if (!dr_analyze_innermost (&DR_INNERMOST (&init_dr), init_ref, loop, init_stmt)) return NULL; if (!valid_initializer_p (&init_dr, ref->distance + 1, root->ref)) return NULL; /* Make sure nothing clobbers the location we re-use the initial value from. */ if (entry_vuse != gimple_vuse (init_stmt)) { ao_ref ref; ao_ref_init (&ref, init_ref); unsigned limit = param_sccvn_max_alias_queries_per_access; tree vdef = entry_vuse; do { gimple *def = SSA_NAME_DEF_STMT (vdef); if (limit-- == 0 || gimple_code (def) == GIMPLE_PHI) return NULL; if (stmt_may_clobber_ref_p_1 (def, &ref)) /* When the stmt is an assign to init_ref we could in theory use its RHS for the initial value of the looparound PHI we replace in prepare_initializers_chain, but we have no convenient place to store this info at the moment. */ return NULL; vdef = gimple_vuse (def); } while (vdef != gimple_vuse (init_stmt)); } return phi; } /* Adds a reference for the looparound copy of REF in PHI to CHAIN. */ static void insert_looparound_copy (chain_p chain, dref ref, gphi *phi) { dref nw = XCNEW (class dref_d), aref; unsigned i; nw->stmt = phi; nw->distance = ref->distance + 1; nw->always_accessed = 1; FOR_EACH_VEC_ELT (chain->refs, i, aref) if (aref->distance >= nw->distance) break; chain->refs.safe_insert (i, nw); if (nw->distance > chain->length) { chain->length = nw->distance; chain->has_max_use_after = false; } } /* For references in CHAIN that are copied around the LOOP (created previously by PRE, or by user), add the results of such copies to the chain. This enables us to remove the copies by unrolling, and may need less registers (also, it may allow us to combine chains together). */ static void add_looparound_copies (class loop *loop, chain_p chain) { unsigned i; dref ref, root = get_chain_root (chain); gphi *phi; if (chain->type == CT_STORE_STORE) return; FOR_EACH_VEC_ELT (chain->refs, i, ref) { phi = find_looparound_phi (loop, ref, root); if (!phi) continue; bitmap_set_bit (looparound_phis, SSA_NAME_VERSION (PHI_RESULT (phi))); insert_looparound_copy (chain, ref, phi); } } /* Find roots of the values and determine distances in the component COMP. The references are redistributed into CHAINS. LOOP is the current loop. */ static void determine_roots_comp (class loop *loop, struct component *comp, vec *chains) { unsigned i; dref a; chain_p chain = NULL; widest_int last_ofs = 0; enum chain_type type; /* Invariants are handled specially. */ if (comp->comp_step == RS_INVARIANT) { chain = make_invariant_chain (comp); chains->safe_push (chain); return; } /* Trivial component. */ if (comp->refs.length () <= 1) { if (comp->refs.length () == 1) { free (comp->refs[0]); comp->refs.truncate (0); } return; } comp->refs.qsort (order_drefs); /* For Store-Store chain, we only support load if it is dominated by a store statement in the same iteration of loop. */ if (comp->eliminate_store_p) for (a = NULL, i = 0; i < comp->refs.length (); i++) { if (DR_IS_WRITE (comp->refs[i]->ref)) a = comp->refs[i]; else if (a == NULL || a->offset != comp->refs[i]->offset) { /* If there is load that is not dominated by a store in the same iteration of loop, clear the flag so no Store-Store chain is generated for this component. */ comp->eliminate_store_p = false; break; } } /* Determine roots and create chains for components. */ FOR_EACH_VEC_ELT (comp->refs, i, a) { if (!chain || (chain->type == CT_LOAD && DR_IS_WRITE (a->ref)) || (!comp->eliminate_store_p && DR_IS_WRITE (a->ref)) || wi::leu_p (MAX_DISTANCE, a->offset - last_ofs)) { if (nontrivial_chain_p (chain)) { add_looparound_copies (loop, chain); chains->safe_push (chain); } else release_chain (chain); /* Determine type of the chain. If the root reference is a load, this can only be a CT_LOAD chain; other chains are intialized to CT_STORE_LOAD and might be promoted to CT_STORE_STORE when new reference is added. */ type = DR_IS_READ (a->ref) ? CT_LOAD : CT_STORE_LOAD; chain = make_rooted_chain (a, type); last_ofs = a->offset; continue; } add_ref_to_chain (chain, a); } if (nontrivial_chain_p (chain)) { add_looparound_copies (loop, chain); chains->safe_push (chain); } else release_chain (chain); } /* Find roots of the values and determine distances in components COMPS, and separates the references to CHAINS. LOOP is the current loop. */ static void determine_roots (class loop *loop, struct component *comps, vec *chains) { struct component *comp; for (comp = comps; comp; comp = comp->next) determine_roots_comp (loop, comp, chains); } /* Replace the reference in statement STMT with temporary variable NEW_TREE. If SET is true, NEW_TREE is instead initialized to the value of the reference in the statement. IN_LHS is true if the reference is in the lhs of STMT, false if it is in rhs. */ static void replace_ref_with (gimple *stmt, tree new_tree, bool set, bool in_lhs) { tree val; gassign *new_stmt; gimple_stmt_iterator bsi, psi; if (gimple_code (stmt) == GIMPLE_PHI) { gcc_assert (!in_lhs && !set); val = PHI_RESULT (stmt); bsi = gsi_after_labels (gimple_bb (stmt)); psi = gsi_for_stmt (stmt); remove_phi_node (&psi, false); /* Turn the phi node into GIMPLE_ASSIGN. */ new_stmt = gimple_build_assign (val, new_tree); gsi_insert_before (&bsi, new_stmt, GSI_NEW_STMT); return; } /* Since the reference is of gimple_reg type, it should only appear as lhs or rhs of modify statement. */ gcc_assert (is_gimple_assign (stmt)); bsi = gsi_for_stmt (stmt); /* If we do not need to initialize NEW_TREE, just replace the use of OLD. */ if (!set) { gcc_assert (!in_lhs); gimple_assign_set_rhs_from_tree (&bsi, new_tree); stmt = gsi_stmt (bsi); update_stmt (stmt); return; } if (in_lhs) { /* We have statement OLD = VAL If OLD is a memory reference, then VAL is gimple_val, and we transform this to OLD = VAL NEW = VAL Otherwise, we are replacing a combination chain, VAL is the expression that performs the combination, and OLD is an SSA name. In this case, we transform the assignment to OLD = VAL NEW = OLD */ val = gimple_assign_lhs (stmt); if (TREE_CODE (val) != SSA_NAME) { val = gimple_assign_rhs1 (stmt); gcc_assert (gimple_assign_single_p (stmt)); if (TREE_CLOBBER_P (val)) val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (new_tree)); else gcc_assert (gimple_assign_copy_p (stmt)); } } else { /* VAL = OLD is transformed to VAL = OLD NEW = VAL */ val = gimple_assign_lhs (stmt); } new_stmt = gimple_build_assign (new_tree, unshare_expr (val)); gsi_insert_after (&bsi, new_stmt, GSI_NEW_STMT); } /* Returns a memory reference to DR in the (NITERS + ITER)-th iteration of the loop it was analyzed in. Append init stmts to STMTS. */ static tree ref_at_iteration (data_reference_p dr, int iter, gimple_seq *stmts, tree niters = NULL_TREE) { tree off = DR_OFFSET (dr); tree coff = DR_INIT (dr); tree ref = DR_REF (dr); enum tree_code ref_code = ERROR_MARK; tree ref_type = NULL_TREE; tree ref_op1 = NULL_TREE; tree ref_op2 = NULL_TREE; tree new_offset; if (iter != 0) { new_offset = size_binop (MULT_EXPR, DR_STEP (dr), ssize_int (iter)); if (TREE_CODE (new_offset) == INTEGER_CST) coff = size_binop (PLUS_EXPR, coff, new_offset); else off = size_binop (PLUS_EXPR, off, new_offset); } if (niters != NULL_TREE) { niters = fold_convert (ssizetype, niters); new_offset = size_binop (MULT_EXPR, DR_STEP (dr), niters); if (TREE_CODE (niters) == INTEGER_CST) coff = size_binop (PLUS_EXPR, coff, new_offset); else off = size_binop (PLUS_EXPR, off, new_offset); } /* While data-ref analysis punts on bit offsets it still handles bitfield accesses at byte boundaries. Cope with that. Note that if the bitfield object also starts at a byte-boundary we can simply replicate the COMPONENT_REF, but we have to subtract the component's byte-offset from the MEM_REF address first. Otherwise we simply build a BIT_FIELD_REF knowing that the bits start at offset zero. */ if (TREE_CODE (ref) == COMPONENT_REF && DECL_BIT_FIELD (TREE_OPERAND (ref, 1))) { unsigned HOST_WIDE_INT boff; tree field = TREE_OPERAND (ref, 1); tree offset = component_ref_field_offset (ref); ref_type = TREE_TYPE (ref); boff = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)); /* This can occur in Ada. See the comment in get_bit_range. */ if (boff % BITS_PER_UNIT != 0 || !tree_fits_uhwi_p (offset)) { ref_code = BIT_FIELD_REF; ref_op1 = DECL_SIZE (field); ref_op2 = bitsize_zero_node; } else { boff >>= LOG2_BITS_PER_UNIT; boff += tree_to_uhwi (offset); coff = size_binop (MINUS_EXPR, coff, ssize_int (boff)); ref_code = COMPONENT_REF; ref_op1 = field; ref_op2 = TREE_OPERAND (ref, 2); ref = TREE_OPERAND (ref, 0); } } tree addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off); addr = force_gimple_operand_1 (unshare_expr (addr), stmts, is_gimple_mem_ref_addr, NULL_TREE); tree alias_ptr = fold_convert (reference_alias_ptr_type (ref), coff); tree type = build_aligned_type (TREE_TYPE (ref), get_object_alignment (ref)); ref = build2 (MEM_REF, type, addr, alias_ptr); if (ref_type) ref = build3 (ref_code, ref_type, ref, ref_op1, ref_op2); return ref; } /* Get the initialization expression for the INDEX-th temporary variable of CHAIN. */ static tree get_init_expr (chain_p chain, unsigned index) { if (chain->type == CT_COMBINATION) { tree e1 = get_init_expr (chain->ch1, index); tree e2 = get_init_expr (chain->ch2, index); return fold_build2 (chain->op, chain->rslt_type, e1, e2); } else return chain->inits[index]; } /* Returns a new temporary variable used for the I-th variable carrying value of REF. The variable's uid is marked in TMP_VARS. */ static tree predcom_tmp_var (tree ref, unsigned i, bitmap tmp_vars) { tree type = TREE_TYPE (ref); /* We never access the components of the temporary variable in predictive commoning. */ tree var = create_tmp_reg (type, get_lsm_tmp_name (ref, i)); bitmap_set_bit (tmp_vars, DECL_UID (var)); return var; } /* Creates the variables for CHAIN, as well as phi nodes for them and initialization on entry to LOOP. Uids of the newly created temporary variables are marked in TMP_VARS. */ static void initialize_root_vars (class loop *loop, chain_p chain, bitmap tmp_vars) { unsigned i; unsigned n = chain->length; dref root = get_chain_root (chain); bool reuse_first = !chain->has_max_use_after; tree ref, init, var, next; gphi *phi; gimple_seq stmts; edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop); /* If N == 0, then all the references are within the single iteration. And since this is an nonempty chain, reuse_first cannot be true. */ gcc_assert (n > 0 || !reuse_first); chain->vars.create (n + 1); if (chain->type == CT_COMBINATION) ref = gimple_assign_lhs (root->stmt); else ref = DR_REF (root->ref); for (i = 0; i < n + (reuse_first ? 0 : 1); i++) { var = predcom_tmp_var (ref, i, tmp_vars); chain->vars.quick_push (var); } if (reuse_first) chain->vars.quick_push (chain->vars[0]); FOR_EACH_VEC_ELT (chain->vars, i, var) chain->vars[i] = make_ssa_name (var); for (i = 0; i < n; i++) { var = chain->vars[i]; next = chain->vars[i + 1]; init = get_init_expr (chain, i); init = force_gimple_operand (init, &stmts, true, NULL_TREE); if (stmts) gsi_insert_seq_on_edge_immediate (entry, stmts); phi = create_phi_node (var, loop->header); add_phi_arg (phi, init, entry, UNKNOWN_LOCATION); add_phi_arg (phi, next, latch, UNKNOWN_LOCATION); } } /* For inter-iteration store elimination CHAIN in LOOP, returns true if all stores to be eliminated store loop invariant values into memory. In this case, we can use these invariant values directly after LOOP. */ static bool is_inv_store_elimination_chain (class loop *loop, chain_p chain) { if (chain->length == 0 || chain->type != CT_STORE_STORE) return false; gcc_assert (!chain->has_max_use_after); /* If loop iterates for unknown times or fewer times than chain->length, we still need to setup root variable and propagate it with PHI node. */ tree niters = number_of_latch_executions (loop); if (TREE_CODE (niters) != INTEGER_CST || wi::leu_p (wi::to_wide (niters), chain->length)) return false; /* Check stores in chain for elimination if they only store loop invariant values. */ for (unsigned i = 0; i < chain->length; i++) { dref a = get_chain_last_write_at (chain, i); if (a == NULL) continue; gimple *def_stmt, *stmt = a->stmt; if (!gimple_assign_single_p (stmt)) return false; tree val = gimple_assign_rhs1 (stmt); if (TREE_CLOBBER_P (val)) return false; if (CONSTANT_CLASS_P (val)) continue; if (TREE_CODE (val) != SSA_NAME) return false; def_stmt = SSA_NAME_DEF_STMT (val); if (gimple_nop_p (def_stmt)) continue; if (flow_bb_inside_loop_p (loop, gimple_bb (def_stmt))) return false; } return true; } /* Creates root variables for store elimination CHAIN in which stores for elimination only store loop invariant values. In this case, we neither need to load root variables before loop nor propagate it with PHI nodes. */ static void initialize_root_vars_store_elim_1 (chain_p chain) { tree var; unsigned i, n = chain->length; chain->vars.create (n); chain->vars.safe_grow_cleared (n); /* Initialize root value for eliminated stores at each distance. */ for (i = 0; i < n; i++) { dref a = get_chain_last_write_at (chain, i); if (a == NULL) continue; var = gimple_assign_rhs1 (a->stmt); chain->vars[a->distance] = var; } /* We don't propagate values with PHI nodes, so manually propagate value to bubble positions. */ var = chain->vars[0]; for (i = 1; i < n; i++) { if (chain->vars[i] != NULL_TREE) { var = chain->vars[i]; continue; } chain->vars[i] = var; } /* Revert the vector. */ for (i = 0; i < n / 2; i++) std::swap (chain->vars[i], chain->vars[n - i - 1]); } /* Creates root variables for store elimination CHAIN in which stores for elimination store loop variant values. In this case, we may need to load root variables before LOOP and propagate it with PHI nodes. Uids of the newly created root variables are marked in TMP_VARS. */ static void initialize_root_vars_store_elim_2 (class loop *loop, chain_p chain, bitmap tmp_vars) { unsigned i, n = chain->length; tree ref, init, var, next, val, phi_result; gimple *stmt; gimple_seq stmts; chain->vars.create (n); ref = DR_REF (get_chain_root (chain)->ref); for (i = 0; i < n; i++) { var = predcom_tmp_var (ref, i, tmp_vars); chain->vars.quick_push (var); } FOR_EACH_VEC_ELT (chain->vars, i, var) chain->vars[i] = make_ssa_name (var); /* Root values are either rhs operand of stores to be eliminated, or loaded from memory before loop. */ auto_vec vtemps; vtemps.safe_grow_cleared (n); for (i = 0; i < n; i++) { init = get_init_expr (chain, i); if (init == NULL_TREE) { /* Root value is rhs operand of the store to be eliminated if it isn't loaded from memory before loop. */ dref a = get_chain_last_write_at (chain, i); val = gimple_assign_rhs1 (a->stmt); if (TREE_CLOBBER_P (val)) { val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (var)); gimple_assign_set_rhs1 (a->stmt, val); } vtemps[n - i - 1] = val; } else { edge latch = loop_latch_edge (loop); edge entry = loop_preheader_edge (loop); /* Root value is loaded from memory before loop, we also need to add PHI nodes to propagate the value across iterations. */ init = force_gimple_operand (init, &stmts, true, NULL_TREE); if (stmts) gsi_insert_seq_on_edge_immediate (entry, stmts); next = chain->vars[n - i]; phi_result = copy_ssa_name (next); gphi *phi = create_phi_node (phi_result, loop->header); add_phi_arg (phi, init, entry, UNKNOWN_LOCATION); add_phi_arg (phi, next, latch, UNKNOWN_LOCATION); vtemps[n - i - 1] = phi_result; } } /* Find the insertion position. */ dref last = get_chain_root (chain); for (i = 0; i < chain->refs.length (); i++) { if (chain->refs[i]->pos > last->pos) last = chain->refs[i]; } gimple_stmt_iterator gsi = gsi_for_stmt (last->stmt); /* Insert statements copying root value to root variable. */ for (i = 0; i < n; i++) { var = chain->vars[i]; val = vtemps[i]; stmt = gimple_build_assign (var, val); gsi_insert_after (&gsi, stmt, GSI_NEW_STMT); } } /* Generates stores for CHAIN's eliminated stores in LOOP's last (CHAIN->length - 1) iterations. */ static void finalize_eliminated_stores (class loop *loop, chain_p chain) { unsigned i, n = chain->length; for (i = 0; i < n; i++) { tree var = chain->vars[i]; tree fini = chain->finis[n - i - 1]; gimple *stmt = gimple_build_assign (fini, var); gimple_seq_add_stmt_without_update (&chain->fini_seq, stmt); } if (chain->fini_seq) { gsi_insert_seq_on_edge_immediate (single_exit (loop), chain->fini_seq); chain->fini_seq = NULL; } } /* Initializes a variable for load motion for ROOT and prepares phi nodes and initialization on entry to LOOP if necessary. The ssa name for the variable is stored in VARS. If WRITTEN is true, also a phi node to copy its value around the loop is created. Uid of the newly created temporary variable is marked in TMP_VARS. INITS is the list containing the (single) initializer. */ static void initialize_root_vars_lm (class loop *loop, dref root, bool written, vec *vars, vec inits, bitmap tmp_vars) { unsigned i; tree ref = DR_REF (root->ref), init, var, next; gimple_seq stmts; gphi *phi; edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop); /* Find the initializer for the variable, and check that it cannot trap. */ init = inits[0]; vars->create (written ? 2 : 1); var = predcom_tmp_var (ref, 0, tmp_vars); vars->quick_push (var); if (written) vars->quick_push ((*vars)[0]); FOR_EACH_VEC_ELT (*vars, i, var) (*vars)[i] = make_ssa_name (var); var = (*vars)[0]; init = force_gimple_operand (init, &stmts, written, NULL_TREE); if (stmts) gsi_insert_seq_on_edge_immediate (entry, stmts); if (written) { next = (*vars)[1]; phi = create_phi_node (var, loop->header); add_phi_arg (phi, init, entry, UNKNOWN_LOCATION); add_phi_arg (phi, next, latch, UNKNOWN_LOCATION); } else { gassign *init_stmt = gimple_build_assign (var, init); gsi_insert_on_edge_immediate (entry, init_stmt); } } /* Execute load motion for references in chain CHAIN. Uids of the newly created temporary variables are marked in TMP_VARS. */ static void execute_load_motion (class loop *loop, chain_p chain, bitmap tmp_vars) { auto_vec vars; dref a; unsigned n_writes = 0, ridx, i; tree var; gcc_assert (chain->type == CT_INVARIANT); gcc_assert (!chain->combined); FOR_EACH_VEC_ELT (chain->refs, i, a) if (DR_IS_WRITE (a->ref)) n_writes++; /* If there are no reads in the loop, there is nothing to do. */ if (n_writes == chain->refs.length ()) return; initialize_root_vars_lm (loop, get_chain_root (chain), n_writes > 0, &vars, chain->inits, tmp_vars); ridx = 0; FOR_EACH_VEC_ELT (chain->refs, i, a) { bool is_read = DR_IS_READ (a->ref); if (DR_IS_WRITE (a->ref)) { n_writes--; if (n_writes) { var = vars[0]; var = make_ssa_name (SSA_NAME_VAR (var)); vars[0] = var; } else ridx = 1; } replace_ref_with (a->stmt, vars[ridx], !is_read, !is_read); } } /* Returns the single statement in that NAME is used, excepting the looparound phi nodes contained in one of the chains. If there is no such statement, or more statements, NULL is returned. */ static gimple * single_nonlooparound_use (tree name) { use_operand_p use; imm_use_iterator it; gimple *stmt, *ret = NULL; FOR_EACH_IMM_USE_FAST (use, it, name) { stmt = USE_STMT (use); if (gimple_code (stmt) == GIMPLE_PHI) { /* Ignore uses in looparound phi nodes. Uses in other phi nodes could not be processed anyway, so just fail for them. */ if (bitmap_bit_p (looparound_phis, SSA_NAME_VERSION (PHI_RESULT (stmt)))) continue; return NULL; } else if (is_gimple_debug (stmt)) continue; else if (ret != NULL) return NULL; else ret = stmt; } return ret; } /* Remove statement STMT, as well as the chain of assignments in that it is used. */ static void remove_stmt (gimple *stmt) { tree name; gimple *next; gimple_stmt_iterator psi; if (gimple_code (stmt) == GIMPLE_PHI) { name = PHI_RESULT (stmt); next = single_nonlooparound_use (name); reset_debug_uses (stmt); psi = gsi_for_stmt (stmt); remove_phi_node (&psi, true); if (!next || !gimple_assign_ssa_name_copy_p (next) || gimple_assign_rhs1 (next) != name) return; stmt = next; } while (1) { gimple_stmt_iterator bsi; bsi = gsi_for_stmt (stmt); name = gimple_assign_lhs (stmt); if (TREE_CODE (name) == SSA_NAME) { next = single_nonlooparound_use (name); reset_debug_uses (stmt); } else { /* This is a store to be eliminated. */ gcc_assert (gimple_vdef (stmt) != NULL); next = NULL; } unlink_stmt_vdef (stmt); gsi_remove (&bsi, true); release_defs (stmt); if (!next || !gimple_assign_ssa_name_copy_p (next) || gimple_assign_rhs1 (next) != name) return; stmt = next; } } /* Perform the predictive commoning optimization for a chain CHAIN. Uids of the newly created temporary variables are marked in TMP_VARS.*/ static void execute_pred_commoning_chain (class loop *loop, chain_p chain, bitmap tmp_vars) { unsigned i; dref a; tree var; bool in_lhs; if (chain->combined) { /* For combined chains, just remove the statements that are used to compute the values of the expression (except for the root one). We delay this until after all chains are processed. */ } else if (chain->type == CT_STORE_STORE) { if (chain->length > 0) { if (chain->inv_store_elimination) { /* If dead stores in this chain only store loop invariant values, we can simply record the invariant value and use it directly after loop. */ initialize_root_vars_store_elim_1 (chain); } else { /* If dead stores in this chain store loop variant values, we need to set up the variables by loading from memory before loop and propagating it with PHI nodes. */ initialize_root_vars_store_elim_2 (loop, chain, tmp_vars); } /* For inter-iteration store elimination chain, stores at each distance in loop's last (chain->length - 1) iterations can't be eliminated, because there is no following killing store. We need to generate these stores after loop. */ finalize_eliminated_stores (loop, chain); } bool last_store_p = true; for (i = chain->refs.length (); i > 0; i--) { a = chain->refs[i - 1]; /* Preserve the last store of the chain. Eliminate other stores which are killed by the last one. */ if (DR_IS_WRITE (a->ref)) { if (last_store_p) last_store_p = false; else remove_stmt (a->stmt); continue; } /* Any load in Store-Store chain must be dominated by a previous store, we replace the load reference with rhs of the store. */ dref b = get_chain_last_write_before_load (chain, i - 1); gcc_assert (b != NULL); var = gimple_assign_rhs1 (b->stmt); replace_ref_with (a->stmt, var, false, false); } } else { /* For non-combined chains, set up the variables that hold its value. */ initialize_root_vars (loop, chain, tmp_vars); a = get_chain_root (chain); in_lhs = (chain->type == CT_STORE_LOAD || chain->type == CT_COMBINATION); replace_ref_with (a->stmt, chain->vars[chain->length], true, in_lhs); /* Replace the uses of the original references by these variables. */ for (i = 1; chain->refs.iterate (i, &a); i++) { var = chain->vars[chain->length - a->distance]; replace_ref_with (a->stmt, var, false, false); } } } /* Determines the unroll factor necessary to remove as many temporary variable copies as possible. CHAINS is the list of chains that will be optimized. */ static unsigned determine_unroll_factor (vec chains) { chain_p chain; unsigned factor = 1, af, nfactor, i; unsigned max = param_max_unroll_times; FOR_EACH_VEC_ELT (chains, i, chain) { if (chain->type == CT_INVARIANT) continue; /* For now we can't handle unrolling when eliminating stores. */ else if (chain->type == CT_STORE_STORE) return 1; if (chain->combined) { /* For combined chains, we can't handle unrolling if we replace looparound PHIs. */ dref a; unsigned j; for (j = 1; chain->refs.iterate (j, &a); j++) if (gimple_code (a->stmt) == GIMPLE_PHI) return 1; continue; } /* The best unroll factor for this chain is equal to the number of temporary variables that we create for it. */ af = chain->length; if (chain->has_max_use_after) af++; nfactor = factor * af / gcd (factor, af); if (nfactor <= max) factor = nfactor; } return factor; } /* Perform the predictive commoning optimization for CHAINS. Uids of the newly created temporary variables are marked in TMP_VARS. */ static void execute_pred_commoning (class loop *loop, vec chains, bitmap tmp_vars) { chain_p chain; unsigned i; FOR_EACH_VEC_ELT (chains, i, chain) { if (chain->type == CT_INVARIANT) execute_load_motion (loop, chain, tmp_vars); else execute_pred_commoning_chain (loop, chain, tmp_vars); } FOR_EACH_VEC_ELT (chains, i, chain) { if (chain->type == CT_INVARIANT) ; else if (chain->combined) { /* For combined chains, just remove the statements that are used to compute the values of the expression (except for the root one). */ dref a; unsigned j; for (j = 1; chain->refs.iterate (j, &a); j++) remove_stmt (a->stmt); } } update_ssa (TODO_update_ssa_only_virtuals); } /* For each reference in CHAINS, if its defining statement is phi node, record the ssa name that is defined by it. */ static void replace_phis_by_defined_names (vec chains) { chain_p chain; dref a; unsigned i, j; FOR_EACH_VEC_ELT (chains, i, chain) FOR_EACH_VEC_ELT (chain->refs, j, a) { if (gimple_code (a->stmt) == GIMPLE_PHI) { a->name_defined_by_phi = PHI_RESULT (a->stmt); a->stmt = NULL; } } } /* For each reference in CHAINS, if name_defined_by_phi is not NULL, use it to set the stmt field. */ static void replace_names_by_phis (vec chains) { chain_p chain; dref a; unsigned i, j; FOR_EACH_VEC_ELT (chains, i, chain) FOR_EACH_VEC_ELT (chain->refs, j, a) if (a->stmt == NULL) { a->stmt = SSA_NAME_DEF_STMT (a->name_defined_by_phi); gcc_assert (gimple_code (a->stmt) == GIMPLE_PHI); a->name_defined_by_phi = NULL_TREE; } } /* Wrapper over execute_pred_commoning, to pass it as a callback to tree_transform_and_unroll_loop. */ struct epcc_data { vec chains; bitmap tmp_vars; }; static void execute_pred_commoning_cbck (class loop *loop, void *data) { struct epcc_data *const dta = (struct epcc_data *) data; /* Restore phi nodes that were replaced by ssa names before tree_transform_and_unroll_loop (see detailed description in tree_predictive_commoning_loop). */ replace_names_by_phis (dta->chains); execute_pred_commoning (loop, dta->chains, dta->tmp_vars); } /* Base NAME and all the names in the chain of phi nodes that use it on variable VAR. The phi nodes are recognized by being in the copies of the header of the LOOP. */ static void base_names_in_chain_on (class loop *loop, tree name, tree var) { gimple *stmt, *phi; imm_use_iterator iter; replace_ssa_name_symbol (name, var); while (1) { phi = NULL; FOR_EACH_IMM_USE_STMT (stmt, iter, name) { if (gimple_code (stmt) == GIMPLE_PHI && flow_bb_inside_loop_p (loop, gimple_bb (stmt))) { phi = stmt; BREAK_FROM_IMM_USE_STMT (iter); } } if (!phi) return; name = PHI_RESULT (phi); replace_ssa_name_symbol (name, var); } } /* Given an unrolled LOOP after predictive commoning, remove the register copies arising from phi nodes by changing the base variables of SSA names. TMP_VARS is the set of the temporary variables for those we want to perform this. */ static void eliminate_temp_copies (class loop *loop, bitmap tmp_vars) { edge e; gphi *phi; gimple *stmt; tree name, use, var; gphi_iterator psi; e = loop_latch_edge (loop); for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi)) { phi = psi.phi (); name = PHI_RESULT (phi); var = SSA_NAME_VAR (name); if (!var || !bitmap_bit_p (tmp_vars, DECL_UID (var))) continue; use = PHI_ARG_DEF_FROM_EDGE (phi, e); gcc_assert (TREE_CODE (use) == SSA_NAME); /* Base all the ssa names in the ud and du chain of NAME on VAR. */ stmt = SSA_NAME_DEF_STMT (use); while (gimple_code (stmt) == GIMPLE_PHI /* In case we could not unroll the loop enough to eliminate all copies, we may reach the loop header before the defining statement (in that case, some register copies will be present in loop latch in the final code, corresponding to the newly created looparound phi nodes). */ && gimple_bb (stmt) != loop->header) { gcc_assert (single_pred_p (gimple_bb (stmt))); use = PHI_ARG_DEF (stmt, 0); stmt = SSA_NAME_DEF_STMT (use); } base_names_in_chain_on (loop, use, var); } } /* Returns true if CHAIN is suitable to be combined. */ static bool chain_can_be_combined_p (chain_p chain) { return (!chain->combined && (chain->type == CT_LOAD || chain->type == CT_COMBINATION)); } /* Returns the modify statement that uses NAME. Skips over assignment statements, NAME is replaced with the actual name used in the returned statement. */ static gimple * find_use_stmt (tree *name) { gimple *stmt; tree rhs, lhs; /* Skip over assignments. */ while (1) { stmt = single_nonlooparound_use (*name); if (!stmt) return NULL; if (gimple_code (stmt) != GIMPLE_ASSIGN) return NULL; lhs = gimple_assign_lhs (stmt); if (TREE_CODE (lhs) != SSA_NAME) return NULL; if (gimple_assign_copy_p (stmt)) { rhs = gimple_assign_rhs1 (stmt); if (rhs != *name) return NULL; *name = lhs; } else if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt)) == GIMPLE_BINARY_RHS) return stmt; else return NULL; } } /* Returns true if we may perform reassociation for operation CODE in TYPE. */ static bool may_reassociate_p (tree type, enum tree_code code) { if (FLOAT_TYPE_P (type) && !flag_unsafe_math_optimizations) return false; return (commutative_tree_code (code) && associative_tree_code (code)); } /* If the operation used in STMT is associative and commutative, go through the tree of the same operations and returns its root. Distance to the root is stored in DISTANCE. */ static gimple * find_associative_operation_root (gimple *stmt, unsigned *distance) { tree lhs; gimple *next; enum tree_code code = gimple_assign_rhs_code (stmt); tree type = TREE_TYPE (gimple_assign_lhs (stmt)); unsigned dist = 0; if (!may_reassociate_p (type, code)) return NULL; while (1) { lhs = gimple_assign_lhs (stmt); gcc_assert (TREE_CODE (lhs) == SSA_NAME); next = find_use_stmt (&lhs); if (!next || gimple_assign_rhs_code (next) != code) break; stmt = next; dist++; } if (distance) *distance = dist; return stmt; } /* Returns the common statement in that NAME1 and NAME2 have a use. If there is no such statement, returns NULL_TREE. In case the operation used on NAME1 and NAME2 is associative and commutative, returns the root of the tree formed by this operation instead of the statement that uses NAME1 or NAME2. */ static gimple * find_common_use_stmt (tree *name1, tree *name2) { gimple *stmt1, *stmt2; stmt1 = find_use_stmt (name1); if (!stmt1) return NULL; stmt2 = find_use_stmt (name2); if (!stmt2) return NULL; if (stmt1 == stmt2) return stmt1; stmt1 = find_associative_operation_root (stmt1, NULL); if (!stmt1) return NULL; stmt2 = find_associative_operation_root (stmt2, NULL); if (!stmt2) return NULL; return (stmt1 == stmt2 ? stmt1 : NULL); } /* Checks whether R1 and R2 are combined together using CODE, with the result in RSLT_TYPE, in order R1 CODE R2 if SWAP is false and in order R2 CODE R1 if it is true. If CODE is ERROR_MARK, set these values instead. */ static bool combinable_refs_p (dref r1, dref r2, enum tree_code *code, bool *swap, tree *rslt_type) { enum tree_code acode; bool aswap; tree atype; tree name1, name2; gimple *stmt; name1 = name_for_ref (r1); name2 = name_for_ref (r2); gcc_assert (name1 != NULL_TREE && name2 != NULL_TREE); stmt = find_common_use_stmt (&name1, &name2); if (!stmt /* A simple post-dominance check - make sure the combination is executed under the same condition as the references. */ || (gimple_bb (stmt) != gimple_bb (r1->stmt) && gimple_bb (stmt) != gimple_bb (r2->stmt))) return false; acode = gimple_assign_rhs_code (stmt); aswap = (!commutative_tree_code (acode) && gimple_assign_rhs1 (stmt) != name1); atype = TREE_TYPE (gimple_assign_lhs (stmt)); if (*code == ERROR_MARK) { *code = acode; *swap = aswap; *rslt_type = atype; return true; } return (*code == acode && *swap == aswap && *rslt_type == atype); } /* Remove OP from the operation on rhs of STMT, and replace STMT with an assignment of the remaining operand. */ static void remove_name_from_operation (gimple *stmt, tree op) { tree other_op; gimple_stmt_iterator si; gcc_assert (is_gimple_assign (stmt)); if (gimple_assign_rhs1 (stmt) == op) other_op = gimple_assign_rhs2 (stmt); else other_op = gimple_assign_rhs1 (stmt); si = gsi_for_stmt (stmt); gimple_assign_set_rhs_from_tree (&si, other_op); /* We should not have reallocated STMT. */ gcc_assert (gsi_stmt (si) == stmt); update_stmt (stmt); } /* Reassociates the expression in that NAME1 and NAME2 are used so that they are combined in a single statement, and returns this statement. */ static gimple * reassociate_to_the_same_stmt (tree name1, tree name2) { gimple *stmt1, *stmt2, *root1, *root2, *s1, *s2; gassign *new_stmt, *tmp_stmt; tree new_name, tmp_name, var, r1, r2; unsigned dist1, dist2; enum tree_code code; tree type = TREE_TYPE (name1); gimple_stmt_iterator bsi; stmt1 = find_use_stmt (&name1); stmt2 = find_use_stmt (&name2); root1 = find_associative_operation_root (stmt1, &dist1); root2 = find_associative_operation_root (stmt2, &dist2); code = gimple_assign_rhs_code (stmt1); gcc_assert (root1 && root2 && root1 == root2 && code == gimple_assign_rhs_code (stmt2)); /* Find the root of the nearest expression in that both NAME1 and NAME2 are used. */ r1 = name1; s1 = stmt1; r2 = name2; s2 = stmt2; while (dist1 > dist2) { s1 = find_use_stmt (&r1); r1 = gimple_assign_lhs (s1); dist1--; } while (dist2 > dist1) { s2 = find_use_stmt (&r2); r2 = gimple_assign_lhs (s2); dist2--; } while (s1 != s2) { s1 = find_use_stmt (&r1); r1 = gimple_assign_lhs (s1); s2 = find_use_stmt (&r2); r2 = gimple_assign_lhs (s2); } /* Remove NAME1 and NAME2 from the statements in that they are used currently. */ remove_name_from_operation (stmt1, name1); remove_name_from_operation (stmt2, name2); /* Insert the new statement combining NAME1 and NAME2 before S1, and combine it with the rhs of S1. */ var = create_tmp_reg (type, "predreastmp"); new_name = make_ssa_name (var); new_stmt = gimple_build_assign (new_name, code, name1, name2); var = create_tmp_reg (type, "predreastmp"); tmp_name = make_ssa_name (var); /* Rhs of S1 may now be either a binary expression with operation CODE, or gimple_val (in case that stmt1 == s1 or stmt2 == s1, so that name1 or name2 was removed from it). */ tmp_stmt = gimple_build_assign (tmp_name, gimple_assign_rhs_code (s1), gimple_assign_rhs1 (s1), gimple_assign_rhs2 (s1)); bsi = gsi_for_stmt (s1); gimple_assign_set_rhs_with_ops (&bsi, code, new_name, tmp_name); s1 = gsi_stmt (bsi); update_stmt (s1); gsi_insert_before (&bsi, new_stmt, GSI_SAME_STMT); gsi_insert_before (&bsi, tmp_stmt, GSI_SAME_STMT); return new_stmt; } /* Returns the statement that combines references R1 and R2. In case R1 and R2 are not used in the same statement, but they are used with an associative and commutative operation in the same expression, reassociate the expression so that they are used in the same statement. */ static gimple * stmt_combining_refs (dref r1, dref r2) { gimple *stmt1, *stmt2; tree name1 = name_for_ref (r1); tree name2 = name_for_ref (r2); stmt1 = find_use_stmt (&name1); stmt2 = find_use_stmt (&name2); if (stmt1 == stmt2) return stmt1; return reassociate_to_the_same_stmt (name1, name2); } /* Tries to combine chains CH1 and CH2 together. If this succeeds, the description of the new chain is returned, otherwise we return NULL. */ static chain_p combine_chains (chain_p ch1, chain_p ch2) { dref r1, r2, nw; enum tree_code op = ERROR_MARK; bool swap = false; chain_p new_chain; unsigned i; tree rslt_type = NULL_TREE; if (ch1 == ch2) return NULL; if (ch1->length != ch2->length) return NULL; if (ch1->refs.length () != ch2->refs.length ()) return NULL; for (i = 0; (ch1->refs.iterate (i, &r1) && ch2->refs.iterate (i, &r2)); i++) { if (r1->distance != r2->distance) return NULL; if (!combinable_refs_p (r1, r2, &op, &swap, &rslt_type)) return NULL; } if (swap) std::swap (ch1, ch2); new_chain = XCNEW (struct chain); new_chain->type = CT_COMBINATION; new_chain->op = op; new_chain->ch1 = ch1; new_chain->ch2 = ch2; new_chain->rslt_type = rslt_type; new_chain->length = ch1->length; for (i = 0; (ch1->refs.iterate (i, &r1) && ch2->refs.iterate (i, &r2)); i++) { nw = XCNEW (class dref_d); nw->stmt = stmt_combining_refs (r1, r2); nw->distance = r1->distance; new_chain->refs.safe_push (nw); } ch1->combined = true; ch2->combined = true; return new_chain; } /* Recursively update position information of all offspring chains to ROOT chain's position information. */ static void update_pos_for_combined_chains (chain_p root) { chain_p ch1 = root->ch1, ch2 = root->ch2; dref ref, ref1, ref2; for (unsigned j = 0; (root->refs.iterate (j, &ref) && ch1->refs.iterate (j, &ref1) && ch2->refs.iterate (j, &ref2)); ++j) ref1->pos = ref2->pos = ref->pos; if (ch1->type == CT_COMBINATION) update_pos_for_combined_chains (ch1); if (ch2->type == CT_COMBINATION) update_pos_for_combined_chains (ch2); } /* Returns true if statement S1 dominates statement S2. */ static bool pcom_stmt_dominates_stmt_p (gimple *s1, gimple *s2) { basic_block bb1 = gimple_bb (s1), bb2 = gimple_bb (s2); if (!bb1 || s1 == s2) return true; if (bb1 == bb2) return gimple_uid (s1) < gimple_uid (s2); return dominated_by_p (CDI_DOMINATORS, bb2, bb1); } /* Try to combine the CHAINS in LOOP. */ static void try_combine_chains (class loop *loop, vec *chains) { unsigned i, j; chain_p ch1, ch2, cch; auto_vec worklist; bool combined_p = false; FOR_EACH_VEC_ELT (*chains, i, ch1) if (chain_can_be_combined_p (ch1)) worklist.safe_push (ch1); while (!worklist.is_empty ()) { ch1 = worklist.pop (); if (!chain_can_be_combined_p (ch1)) continue; FOR_EACH_VEC_ELT (*chains, j, ch2) { if (!chain_can_be_combined_p (ch2)) continue; cch = combine_chains (ch1, ch2); if (cch) { worklist.safe_push (cch); chains->safe_push (cch); combined_p = true; break; } } } if (!combined_p) return; /* Setup UID for all statements in dominance order. */ basic_block *bbs = get_loop_body_in_dom_order (loop); renumber_gimple_stmt_uids_in_blocks (bbs, loop->num_nodes); free (bbs); /* Re-association in combined chains may generate statements different to order of references of the original chain. We need to keep references of combined chain in dominance order so that all uses will be inserted after definitions. Note: A) This is necessary for all combined chains. B) This is only necessary for ZERO distance references because other references inherit value from loop carried PHIs. We first update position information for all combined chains. */ dref ref; for (i = 0; chains->iterate (i, &ch1); ++i) { if (ch1->type != CT_COMBINATION || ch1->combined) continue; for (j = 0; ch1->refs.iterate (j, &ref); ++j) ref->pos = gimple_uid (ref->stmt); update_pos_for_combined_chains (ch1); } /* Then sort references according to newly updated position information. */ for (i = 0; chains->iterate (i, &ch1); ++i) { if (ch1->type != CT_COMBINATION && !ch1->combined) continue; /* Find the first reference with non-ZERO distance. */ if (ch1->length == 0) j = ch1->refs.length(); else { for (j = 0; ch1->refs.iterate (j, &ref); ++j) if (ref->distance != 0) break; } /* Sort all ZERO distance references by position. */ qsort (&ch1->refs[0], j, sizeof (ch1->refs[0]), order_drefs_by_pos); if (ch1->combined) continue; /* For ZERO length chain, has_max_use_after must be true since root combined stmt must dominates others. */ if (ch1->length == 0) { ch1->has_max_use_after = true; continue; } /* Check if there is use at max distance after root for combined chains and set flag accordingly. */ ch1->has_max_use_after = false; gimple *root_stmt = get_chain_root (ch1)->stmt; for (j = 1; ch1->refs.iterate (j, &ref); ++j) { if (ref->distance == ch1->length && !pcom_stmt_dominates_stmt_p (ref->stmt, root_stmt)) { ch1->has_max_use_after = true; break; } } } } /* Prepare initializers for store elimination CHAIN in LOOP. Returns false if this is impossible because one of these initializers may trap, true otherwise. */ static bool prepare_initializers_chain_store_elim (class loop *loop, chain_p chain) { unsigned i, n = chain->length; /* For now we can't eliminate stores if some of them are conditional executed. */ if (!chain->all_always_accessed) return false; /* Nothing to intialize for intra-iteration store elimination. */ if (n == 0 && chain->type == CT_STORE_STORE) return true; /* For store elimination chain, there is nothing to initialize if stores to be eliminated only store loop invariant values into memory. */ if (chain->type == CT_STORE_STORE && is_inv_store_elimination_chain (loop, chain)) { chain->inv_store_elimination = true; return true; } chain->inits.create (n); chain->inits.safe_grow_cleared (n); /* For store eliminatin chain like below: for (i = 0; i < len; i++) { a[i] = 1; // a[i + 1] = ... a[i + 2] = 3; } store to a[i + 1] is missed in loop body, it acts like bubbles. The content of a[i + 1] remain the same if the loop iterates fewer times than chain->length. We need to set up root variables for such stores by loading from memory before loop. Note we only need to load bubble elements because loop body is guaranteed to be executed at least once after loop's preheader edge. */ auto_vec bubbles; bubbles.safe_grow_cleared (n + 1); for (i = 0; i < chain->refs.length (); i++) bubbles[chain->refs[i]->distance] = true; struct data_reference *dr = get_chain_root (chain)->ref; for (i = 0; i < n; i++) { if (bubbles[i]) continue; gimple_seq stmts = NULL; tree init = ref_at_iteration (dr, (int) 0 - i, &stmts); if (stmts) gimple_seq_add_seq_without_update (&chain->init_seq, stmts); chain->inits[i] = init; } return true; } /* Prepare initializers for CHAIN in LOOP. Returns false if this is impossible because one of these initializers may trap, true otherwise. */ static bool prepare_initializers_chain (class loop *loop, chain_p chain) { unsigned i, n = (chain->type == CT_INVARIANT) ? 1 : chain->length; struct data_reference *dr = get_chain_root (chain)->ref; tree init; dref laref; edge entry = loop_preheader_edge (loop); if (chain->type == CT_STORE_STORE) return prepare_initializers_chain_store_elim (loop, chain); /* Find the initializers for the variables, and check that they cannot trap. */ chain->inits.create (n); for (i = 0; i < n; i++) chain->inits.quick_push (NULL_TREE); /* If we have replaced some looparound phi nodes, use their initializers instead of creating our own. */ FOR_EACH_VEC_ELT (chain->refs, i, laref) { if (gimple_code (laref->stmt) != GIMPLE_PHI) continue; gcc_assert (laref->distance > 0); chain->inits[n - laref->distance] = PHI_ARG_DEF_FROM_EDGE (laref->stmt, entry); } for (i = 0; i < n; i++) { gimple_seq stmts = NULL; if (chain->inits[i] != NULL_TREE) continue; init = ref_at_iteration (dr, (int) i - n, &stmts); if (!chain->all_always_accessed && tree_could_trap_p (init)) { gimple_seq_discard (stmts); return false; } if (stmts) gimple_seq_add_seq_without_update (&chain->init_seq, stmts); chain->inits[i] = init; } return true; } /* Prepare initializers for CHAINS in LOOP, and free chains that cannot be used because the initializers might trap. */ static void prepare_initializers (class loop *loop, vec chains) { chain_p chain; unsigned i; for (i = 0; i < chains.length (); ) { chain = chains[i]; if (prepare_initializers_chain (loop, chain)) i++; else { release_chain (chain); chains.unordered_remove (i); } } } /* Generates finalizer memory references for CHAIN in LOOP. Returns true if finalizer code for CHAIN can be generated, otherwise false. */ static bool prepare_finalizers_chain (class loop *loop, chain_p chain) { unsigned i, n = chain->length; struct data_reference *dr = get_chain_root (chain)->ref; tree fini, niters = number_of_latch_executions (loop); /* For now we can't eliminate stores if some of them are conditional executed. */ if (!chain->all_always_accessed) return false; chain->finis.create (n); for (i = 0; i < n; i++) chain->finis.quick_push (NULL_TREE); /* We never use looparound phi node for store elimination chains. */ /* Find the finalizers for the variables, and check that they cannot trap. */ for (i = 0; i < n; i++) { gimple_seq stmts = NULL; gcc_assert (chain->finis[i] == NULL_TREE); if (TREE_CODE (niters) != INTEGER_CST && TREE_CODE (niters) != SSA_NAME) { niters = unshare_expr (niters); niters = force_gimple_operand (niters, &stmts, true, NULL); if (stmts) { gimple_seq_add_seq_without_update (&chain->fini_seq, stmts); stmts = NULL; } } fini = ref_at_iteration (dr, (int) 0 - i, &stmts, niters); if (stmts) gimple_seq_add_seq_without_update (&chain->fini_seq, stmts); chain->finis[i] = fini; } return true; } /* Generates finalizer memory reference for CHAINS in LOOP. Returns true if finalizer code generation for CHAINS breaks loop closed ssa form. */ static bool prepare_finalizers (class loop *loop, vec chains) { chain_p chain; unsigned i; bool loop_closed_ssa = false; for (i = 0; i < chains.length ();) { chain = chains[i]; /* Finalizer is only necessary for inter-iteration store elimination chains. */ if (chain->length == 0 || chain->type != CT_STORE_STORE) { i++; continue; } if (prepare_finalizers_chain (loop, chain)) { i++; /* Be conservative, assume loop closed ssa form is corrupted by store-store chain. Though it's not always the case if eliminated stores only store loop invariant values into memory. */ loop_closed_ssa = true; } else { release_chain (chain); chains.unordered_remove (i); } } return loop_closed_ssa; } /* Insert all initializing gimple stmts into loop's entry edge. */ static void insert_init_seqs (class loop *loop, vec chains) { unsigned i; edge entry = loop_preheader_edge (loop); for (i = 0; i < chains.length (); ++i) if (chains[i]->init_seq) { gsi_insert_seq_on_edge_immediate (entry, chains[i]->init_seq); chains[i]->init_seq = NULL; } } /* Performs predictive commoning for LOOP. Sets bit 1<<0 of return value if LOOP was unrolled; Sets bit 1<<1 of return value if loop closed ssa form was corrupted. */ static unsigned tree_predictive_commoning_loop (class loop *loop) { vec datarefs; vec dependences; struct component *components; vec chains = vNULL; unsigned unroll_factor; class tree_niter_desc desc; bool unroll = false, loop_closed_ssa = false; edge exit; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Processing loop %d\n", loop->num); /* Nothing for predicitive commoning if loop only iterates 1 time. */ if (get_max_loop_iterations_int (loop) == 0) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Loop iterates only 1 time, nothing to do.\n"); return 0; } /* Find the data references and split them into components according to their dependence relations. */ auto_vec loop_nest; dependences.create (10); datarefs.create (10); if (! compute_data_dependences_for_loop (loop, true, &loop_nest, &datarefs, &dependences)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Cannot analyze data dependencies\n"); free_data_refs (datarefs); free_dependence_relations (dependences); return 0; } if (dump_file && (dump_flags & TDF_DETAILS)) dump_data_dependence_relations (dump_file, dependences); components = split_data_refs_to_components (loop, datarefs, dependences); loop_nest.release (); free_dependence_relations (dependences); if (!components) { free_data_refs (datarefs); free_affine_expand_cache (&name_expansions); return 0; } if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Initial state:\n\n"); dump_components (dump_file, components); } /* Find the suitable components and split them into chains. */ components = filter_suitable_components (loop, components); auto_bitmap tmp_vars; looparound_phis = BITMAP_ALLOC (NULL); determine_roots (loop, components, &chains); release_components (components); if (!chains.exists ()) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Predictive commoning failed: no suitable chains\n"); goto end; } prepare_initializers (loop, chains); loop_closed_ssa = prepare_finalizers (loop, chains); /* Try to combine the chains that are always worked with together. */ try_combine_chains (loop, &chains); insert_init_seqs (loop, chains); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Before commoning:\n\n"); dump_chains (dump_file, chains); } /* Determine the unroll factor, and if the loop should be unrolled, ensure that its number of iterations is divisible by the factor. */ unroll_factor = determine_unroll_factor (chains); scev_reset (); unroll = (unroll_factor > 1 && can_unroll_loop_p (loop, unroll_factor, &desc)); exit = single_dom_exit (loop); /* Execute the predictive commoning transformations, and possibly unroll the loop. */ if (unroll) { struct epcc_data dta; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Unrolling %u times.\n", unroll_factor); dta.chains = chains; dta.tmp_vars = tmp_vars; update_ssa (TODO_update_ssa_only_virtuals); /* Cfg manipulations performed in tree_transform_and_unroll_loop before execute_pred_commoning_cbck is called may cause phi nodes to be reallocated, which is a problem since CHAINS may point to these statements. To fix this, we store the ssa names defined by the phi nodes here instead of the phi nodes themselves, and restore the phi nodes in execute_pred_commoning_cbck. A bit hacky. */ replace_phis_by_defined_names (chains); tree_transform_and_unroll_loop (loop, unroll_factor, exit, &desc, execute_pred_commoning_cbck, &dta); eliminate_temp_copies (loop, tmp_vars); } else { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Executing predictive commoning without unrolling.\n"); execute_pred_commoning (loop, chains, tmp_vars); } end: ; release_chains (chains); free_data_refs (datarefs); BITMAP_FREE (looparound_phis); free_affine_expand_cache (&name_expansions); return (unroll ? 1 : 0) | (loop_closed_ssa ? 2 : 0); } /* Runs predictive commoning. */ unsigned tree_predictive_commoning (void) { class loop *loop; unsigned ret = 0, changed = 0; initialize_original_copy_tables (); FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST) if (optimize_loop_for_speed_p (loop)) { changed |= tree_predictive_commoning_loop (loop); } free_original_copy_tables (); if (changed > 0) { scev_reset (); if (changed > 1) rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa); ret = TODO_cleanup_cfg; } return ret; } /* Predictive commoning Pass. */ static unsigned run_tree_predictive_commoning (struct function *fun) { if (number_of_loops (fun) <= 1) return 0; return tree_predictive_commoning (); } namespace { const pass_data pass_data_predcom = { GIMPLE_PASS, /* type */ "pcom", /* name */ OPTGROUP_LOOP, /* optinfo_flags */ TV_PREDCOM, /* tv_id */ PROP_cfg, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_update_ssa_only_virtuals, /* todo_flags_finish */ }; class pass_predcom : public gimple_opt_pass { public: pass_predcom (gcc::context *ctxt) : gimple_opt_pass (pass_data_predcom, ctxt) {} /* opt_pass methods: */ virtual bool gate (function *) { return flag_predictive_commoning != 0; } virtual unsigned int execute (function *fun) { return run_tree_predictive_commoning (fun); } }; // class pass_predcom } // anon namespace gimple_opt_pass * make_pass_predcom (gcc::context *ctxt) { return new pass_predcom (ctxt); }