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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-08-25 09:40:52 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-08-25 14:25:48 +0200 |
| commit | fd43eab36ea0bb18942e3a7233db2efed4b84b30 (patch) | |
| tree | 47162ba3fa25b6d13b1e18e76e3c4c56f6384162 /flow.c | |
| parent | dc49365a8026fad63297ffde53ca72e4252f4959 (diff) | |
| parent | 13cf4aaeef36031fcee071a1efcf9092b7d7cdf7 (diff) | |
| download | sparse-dev-fd43eab36ea0bb18942e3a7233db2efed4b84b30.tar.gz | |
Merge branch 'kill-dead-stores' into tip
* fix buggy recursion in kill_dead_stores()
* kill dead stores again after memops simplification is done.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Diffstat (limited to 'flow.c')
| -rw-r--r-- | flow.c | 95 |
1 files changed, 73 insertions, 22 deletions
@@ -547,7 +547,21 @@ found: } /* Kill a pseudo that is dead on exit from the bb */ -static void kill_dead_stores(pseudo_t pseudo, unsigned long generation, struct basic_block *bb, int local) +// The context is: +// * the variable is not global but may have its address used (local/non-local) +// * the stores are only needed by others functions which would do some +// loads via the escaped address +// We start by the terminating BB (normal exit BB + no-return/unreachable) +// We walkup the BB' intruction backward +// * we're only concerned by loads, stores & calls +// * if we reach a call -> we have to stop if var is non-local +// * if we reach a load of our var -> we have to stop +// * if we reach a store of our var -> we can kill it, it's dead +// * we can ignore other stores & loads if the var is local +// * if we reach another store or load done via non-symbol access +// (so done via some address calculation) -> we have to stop +// If we reach the top of the BB we can recurse into the parents BBs. +static void kill_dead_stores_bb(pseudo_t pseudo, unsigned long generation, struct basic_block *bb, int local) { struct instruction *insn; struct basic_block *parent; @@ -556,36 +570,33 @@ static void kill_dead_stores(pseudo_t pseudo, unsigned long generation, struct b return; bb->generation = generation; FOR_EACH_PTR_REVERSE(bb->insns, insn) { - int opcode = insn->opcode; - if (!insn->bb) continue; - if (opcode != OP_LOAD && opcode != OP_STORE) { - if (local) - continue; - if (opcode == OP_CALL) + switch (insn->opcode) { + case OP_LOAD: + if (insn->src == pseudo) return; - continue; - } - if (insn->src == pseudo) { - if (opcode == OP_LOAD) + break; + case OP_STORE: + if (insn->src == pseudo) { + kill_instruction_force(insn); + continue; + } + break; + case OP_CALL: + if (!local) return; - kill_instruction_force(insn); + default: continue; } - if (local) - continue; - if (insn->src->type != PSEUDO_SYM) + if (!local && insn->src->type != PSEUDO_SYM) return; } END_FOR_EACH_PTR_REVERSE(insn); FOR_EACH_PTR(bb->parents, parent) { - struct basic_block *child; - FOR_EACH_PTR(parent->children, child) { - if (child && child != bb) - return; - } END_FOR_EACH_PTR(child); - kill_dead_stores(pseudo, generation, parent, local); + if (bb_list_size(parent->children) > 1) + continue; + kill_dead_stores_bb(pseudo, generation, parent, local); } END_FOR_EACH_PTR(parent); } @@ -735,7 +746,7 @@ external_visibility: struct basic_block *bb; FOR_EACH_PTR(ep->bbs, bb) { if (!bb->children) - kill_dead_stores(pseudo, ++bb_generation, bb, !mod); + kill_dead_stores_bb(pseudo, ++bb_generation, bb, !mod); } END_FOR_EACH_PTR(bb); } } @@ -752,6 +763,46 @@ void simplify_symbol_usage(struct entrypoint *ep) } END_FOR_EACH_PTR(pseudo); } +static struct pseudo_user *first_user(pseudo_t p) +{ + struct pseudo_user *pu; + FOR_EACH_PTR(p->users, pu) { + if (!pu) + continue; + return pu; + } END_FOR_EACH_PTR(pu); + return NULL; +} + +void kill_dead_stores(struct entrypoint *ep, pseudo_t addr, int local) +{ + unsigned long generation; + struct basic_block *bb; + + switch (pseudo_user_list_size(addr->users)) { + case 0: + return; + case 1: + if (local) { + struct pseudo_user *pu = first_user(addr); + struct instruction *insn = pu->insn; + if (insn->opcode == OP_STORE) { + kill_instruction_force(insn); + return; + } + } + default: + break; + } + + generation = ++bb_generation; + FOR_EACH_PTR(ep->bbs, bb) { + if (bb->children) + continue; + kill_dead_stores_bb(addr, generation, bb, local); + } END_FOR_EACH_PTR(bb); +} + static void mark_bb_reachable(struct basic_block *bb, unsigned long generation) { struct basic_block *child; |