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Add SSA optimization to remove useless FREE and result var stores #21

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4 changes: 2 additions & 2 deletions Zend/Optimizer/block_pass.c
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Original file line number Diff line number Diff line change
Expand Up @@ -262,7 +262,7 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
VAR_SOURCE(opline->op1) = NULL;
}
break;

#if 0
case ZEND_FREE:
/* Note: Only remove the source if the source is local to this block.
* If it's not local, then the other blocks successors must also eventually either FREE or consume the temporary,
Expand Down Expand Up @@ -330,7 +330,7 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
}
}
break;

#endif
#if 0
/* pre-evaluate functions:
constant(x)
Expand Down
86 changes: 84 additions & 2 deletions Zend/Optimizer/dfa_pass.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,9 @@
#include "zend_inference.h"
#include "zend_dump.h"

#ifndef ZEND_DEBUG_DFA
// #ifndef ZEND_DEBUG_DFA
# define ZEND_DEBUG_DFA ZEND_DEBUG
#endif
// #endif

#if ZEND_DEBUG_DFA
# include "ssa_integrity.c"
Expand Down Expand Up @@ -1076,6 +1076,84 @@ static bool zend_dfa_try_to_replace_result(zend_op_array *op_array, zend_ssa *ss
return 0;
}

static int zend_dfa_remove_only_free_uses(zend_op_array *op_array, zend_ssa *ssa)
{
int times_applied = 0;
for (uint32_t i = 0; i < op_array->last; i++) {
zend_op *opline = op_array->opcodes + i;
if (opline->opcode != ZEND_FREE) {
continue;
}
int op1_use = ssa->ops[i].op1_use;
/* Possible if it's unreachable. */
if (op1_use < 0) {
continue;
}
int definition = ssa->vars[op1_use].definition;
if (definition < 0) {
continue;
}
zend_op *defining_opline = op_array->opcodes + definition;
if (opline->op1_type == IS_TMP_VAR) {
switch (defining_opline->opcode) {
case ZEND_ASSIGN:
case ZEND_ASSIGN_DIM:
case ZEND_ASSIGN_OBJ:
case ZEND_ASSIGN_STATIC_PROP:
case ZEND_ASSIGN_OP:
case ZEND_ASSIGN_DIM_OP:
case ZEND_ASSIGN_OBJ_OP:
case ZEND_ASSIGN_STATIC_PROP_OP:
case ZEND_PRE_INC:
case ZEND_PRE_DEC:
case ZEND_PRE_INC_OBJ:
case ZEND_PRE_DEC_OBJ:
case ZEND_PRE_INC_STATIC_PROP:
case ZEND_PRE_DEC_STATIC_PROP:
break;
default:
continue;
}
} else if (opline->op1_type == IS_VAR) {
switch (defining_opline->opcode) {
case ZEND_FETCH_R:
case ZEND_FETCH_STATIC_PROP_R:
case ZEND_FETCH_DIM_R:
case ZEND_FETCH_OBJ_R:
case ZEND_NEW:
case ZEND_FETCH_THIS:
continue;
default:
break;
}
}
int use;
bool all_free = true;
int result_def = ssa->ops[definition].result_def;
if (result_def < 0) {
continue;
}
FOREACH_USE(ssa->vars + result_def, use) {
if (op_array->opcodes[use].opcode != ZEND_FREE) {
all_free = false;
break;
}
} FOREACH_USE_END();
if (all_free) {
FOREACH_USE(ssa->vars + result_def, use) {
MAKE_NOP(op_array->opcodes + use);
ssa->ops[use].op1_use_chain = -1;
ssa->ops[use].op1_use = -1;
} FOREACH_USE_END();
defining_opline->result_type = IS_UNUSED;
zend_ssa_remove_uses_of_var(ssa, result_def);
zend_ssa_remove_result_def(ssa, ssa->ops + definition);
times_applied++;
}
}
return times_applied;
}

void zend_dfa_optimize_op_array(zend_op_array *op_array, zend_optimizer_ctx *ctx, zend_ssa *ssa, zend_call_info **call_map)
{
if (ctx->debug_level & ZEND_DUMP_BEFORE_DFA_PASS) {
Expand All @@ -1094,6 +1172,10 @@ void zend_dfa_optimize_op_array(zend_op_array *op_array, zend_optimizer_ctx *ctx
ssa_verify_integrity(op_array, ssa, "before dfa");
#endif

if (zend_dfa_remove_only_free_uses(op_array, ssa)) {
remove_nops = 1;
}

if (ZEND_OPTIMIZER_PASS_8 & ctx->optimization_level) {
if (sccp_optimize_op_array(ctx, op_array, ssa, call_map)) {
remove_nops = 1;
Expand Down
16 changes: 6 additions & 10 deletions ext/opcache/tests/opt/gh11245_2.phpt
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Original file line number Diff line number Diff line change
Expand Up @@ -21,15 +21,11 @@ switch (++X::$prop) {
?>
--EXPECTF--
$_main:
; (lines=7, args=0, vars=1, tmps=2)
; (lines=5, args=0, vars=1, tmps=1)
; (after optimizer)
; %s
0000 T1 = PRE_INC_STATIC_PROP string("prop") string("X")
0001 T2 = ISSET_ISEMPTY_CV (empty) CV0($xx)
0002 JMPZ T2 0005
0003 FREE T1
0004 RETURN null
0005 FREE T1
0006 RETURN int(1)
LIVE RANGES:
1: 0001 - 0005 (tmp/var)
0000 PRE_INC_STATIC_PROP string("prop") string("X")
0001 T1 = ISSET_ISEMPTY_CV (empty) CV0($xx)
0002 JMPZ T1 0004
0003 RETURN null
0004 RETURN int(1)