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Set RETURN_VALUE_UNUSED instead of additional FREE opcode, if possible.

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Keep alive dead instructions that have to free two temporary variables.
This commit is contained in:
Dmitry Stogov 2017-07-13 12:30:27 +03:00
parent 94c9b26695
commit 624f76df48
1 changed files with 77 additions and 7 deletions
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84
ext/opcache/Optimizer/dce.c
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@ -276,6 +276,68 @@ static inline zend_bool is_var_dead(context *ctx, int var_num) {
}
}
// Sometimes we can mark the var as EXT_UNUSED
static zend_bool try_remove_var_def(context *ctx, int free_var, int use_chain, zend_op *opline) {
if (use_chain >= 0) {
return 0;
}
zend_ssa_var *var = &ctx->ssa->vars[free_var];
int def = var->definition;
if (def >= 0) {
zend_ssa_op *def_op = &ctx->ssa->ops[def];
if (def_op->result_def == free_var
&& var->phi_use_chain == NULL
&& var->use_chain == (opline - ctx->op_array->opcodes)) {
zend_op *def_opline = &ctx->op_array->opcodes[def];
switch (def_opline->opcode) {
case ZEND_ASSIGN:
case ZEND_ASSIGN_REF:
case ZEND_ASSIGN_DIM:
case ZEND_ASSIGN_OBJ:
case ZEND_ASSIGN_ADD:
case ZEND_ASSIGN_SUB:
case ZEND_ASSIGN_MUL:
case ZEND_ASSIGN_DIV:
case ZEND_ASSIGN_MOD:
case ZEND_ASSIGN_SL:
case ZEND_ASSIGN_SR:
case ZEND_ASSIGN_CONCAT:
case ZEND_ASSIGN_BW_OR:
case ZEND_ASSIGN_BW_AND:
case ZEND_ASSIGN_BW_XOR:
case ZEND_ASSIGN_POW:
case ZEND_PRE_INC:
case ZEND_POST_INC:
case ZEND_PRE_DEC:
case ZEND_POST_DEC:
case ZEND_PRE_INC_OBJ:
case ZEND_POST_INC_OBJ:
case ZEND_PRE_DEC_OBJ:
case ZEND_POST_DEC_OBJ:
case ZEND_DO_ICALL:
case ZEND_DO_UCALL:
case ZEND_DO_FCALL_BY_NAME:
case ZEND_DO_FCALL:
case ZEND_INCLUDE_OR_EVAL:
case ZEND_YIELD:
case ZEND_YIELD_FROM:
case ZEND_ASSERT_CHECK:
def_opline->result_type = IS_UNUSED;
def_opline->result.var = 0;
def_op->result_def = -1;
var->definition = -1;
return 1;
default:
break;
}
}
}
return 0;
}
/* Returns whether the instruction has been DCEd */
static zend_bool dce_instr(context *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
zend_ssa *ssa = ctx->ssa;
@ -291,20 +353,28 @@ static zend_bool dce_instr(context *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
return 0;
}
// TODO Two free vars?
if ((opline->op1_type & (IS_VAR|IS_TMP_VAR)) && !is_var_dead(ctx, ssa_op->op1_use)) {
free_var = ssa_op->op1_use;
free_var_type = opline->op1_type;
} else if ((opline->op2_type & (IS_VAR|IS_TMP_VAR)) && !is_var_dead(ctx, ssa_op->op2_use)) {
free_var = ssa_op->op2_use;
free_var_type = opline->op2_type;
if (!try_remove_var_def(ctx, ssa_op->op1_use, ssa_op->op1_use_chain, opline)) {
free_var = ssa_op->op1_use;
free_var_type = opline->op1_type;
}
}
if ((opline->op2_type & (IS_VAR|IS_TMP_VAR)) && !is_var_dead(ctx, ssa_op->op2_use)) {
if (!try_remove_var_def(ctx, ssa_op->op2_use, ssa_op->op2_use_chain, opline)) {
if (free_var >= 0) {
// TODO: We can't free two vars. Keep instruction alive.
zend_bitset_excl(ctx->instr_dead, opline - ctx->op_array->opcodes);
return 0;
}
free_var = ssa_op->op2_use;
free_var_type = opline->op2_type;
}
}
zend_ssa_rename_defs_of_instr(ctx->ssa, ssa_op);
zend_ssa_remove_instr(ctx->ssa, opline, ssa_op);
if (free_var >= 0) {
// TODO Sometimes we can mark the var as EXT_UNUSED
opline->opcode = ZEND_FREE;
opline->op1.var = (uintptr_t) ZEND_CALL_VAR_NUM(NULL, ssa->vars[free_var].var);
opline->op1_type = free_var_type;