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Another peephole optimization which removes superfluous expressions such as (A + 0), (A - 0), (A * 1) and (A / 1).

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This commit is contained in:
Dale Weiler 2013-10-04 06:46:54 -04:00
parent 263fcfbc2f
commit cc69370575
3 changed files with 45 additions and 3 deletions
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14
ast.c
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@ -438,6 +438,7 @@ bool ast_value_set_name(ast_value *self, const char *name)
ast_binary* ast_binary_new(lex_ctx_t ctx, int op,
ast_expression* left, ast_expression* right)
{
ast_binary *fold;
ast_instantiate(ast_binary, ctx, ast_binary_delete);
ast_expression_init((ast_expression*)self, (ast_expression_codegen*)&ast_binary_codegen);
@ -449,6 +450,15 @@ ast_binary* ast_binary_new(lex_ctx_t ctx, int op,
ast_propagate_effects(self, left);
ast_propagate_effects(self, right);
/*
* Try to fold away superfluous binary operations, such as:
* A * 1, a + 0, etc.
*/
if ((fold = (ast_binary*)fold_superfluous(left, right, op))) {
ast_binary_delete(self);
return fold;
}
if (op >= INSTR_EQ_F && op <= INSTR_GT)
self->expression.vtype = TYPE_FLOAT;
else if (op == INSTR_AND || op == INSTR_OR) {
@ -459,10 +469,8 @@ ast_binary* ast_binary_new(lex_ctx_t ctx, int op,
}
else if (op == INSTR_BITAND || op == INSTR_BITOR)
self->expression.vtype = TYPE_FLOAT;
else if (op == INSTR_MUL_VF || op == INSTR_MUL_FV)
else if (op == INSTR_MUL_FV || op == INSTR_MUL_FV)
self->expression.vtype = TYPE_VECTOR;
else if (op == INSTR_MUL_V)
self->expression.vtype = TYPE_FLOAT;
else
self->expression.vtype = left->vtype;

33
fold.c
View file

@ -796,6 +796,39 @@ ast_expression *fold_intrin(fold_t *fold, const char *intrin, ast_expression **a
#define fold_can_1(X) ((X)->hasvalue && (X)->cvq == CV_CONST)
/*#define fold_can_2(X,Y) (fold_can_1(X) && fold_can_1(Y))*/
ast_expression *fold_superfluous(ast_expression *left, ast_expression *right, int op) {
ast_value *load;
if (!ast_istype(left, ast_value))
return NULL;
load = (ast_value*)right;
switch (op) {
case INSTR_MUL_F:
case INSTR_MUL_V:
case INSTR_MUL_FV:
case INSTR_MUL_VF:
case INSTR_DIV_F:
if (fold_can_1(load) && fold_immvalue_float(load) == 1.0f) {
++opts_optimizationcount[OPTIM_PEEPHOLE];
return (ast_expression*)left;
}
break;
case INSTR_ADD_F:
case INSTR_ADD_V:
case INSTR_SUB_F:
case INSTR_SUB_V:
if (fold_can_1(load) && fold_immvalue_float(load) == 0.0f) {
++opts_optimizationcount[OPTIM_PEEPHOLE];
return (ast_expression*)left;
}
break;
}
return NULL;
}
static GMQCC_INLINE int fold_cond(ir_value *condval, ast_function *func, ast_ifthen *branch) {
if (isfloat(condval) && fold_can_1(condval) && OPTS_OPTIMIZATION(OPTIM_CONST_FOLD_DCE)) {

1
parser.h
View file

@ -133,6 +133,7 @@ bool fold_generate (fold_t *, ir_builder *);
ast_expression *fold_op (fold_t *, const oper_info *, ast_expression **);
ast_expression *fold_intrin (fold_t *, const char *, ast_expression **);
ast_expression *fold_superfluous (ast_expression *, ast_expression *, int);
int fold_cond_ifthen (ir_value *, ast_function *, ast_ifthen *);
int fold_cond_ternary (ir_value *, ast_function *, ast_ternary *);