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nir/peephole_ffma: Be less agressive about fusing multiply-adds

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shader-db results for fragment shaders on Haswell:
total instructions in shared programs: 4395688 -> 4389623 (-0.14%)
instructions in affected programs:     355876 -> 349811 (-1.70%)
helped:                                1455
HURT:                                  14
GAINED:                                5
LOST:                                  0

Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Jason Ekstrand 2015-03-23 14:55:20 -07:00
parent a8c8b3b872
commit 7f344721b1
1 changed files with 41 additions and 0 deletions
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41
src/glsl/nir/nir_opt_peephole_ffma.c
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@ -38,6 +38,41 @@ struct peephole_ffma_state {
bool progress;
};
static inline bool
are_all_uses_fadd(nir_ssa_def *def)
{
if (def->if_uses->entries > 0)
return false;
struct set_entry *use_iter;
set_foreach(def->uses, use_iter) {
nir_instr *use_instr = (nir_instr *)use_iter->key;
if (use_instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *use_alu = nir_instr_as_alu(use_instr);
switch (use_alu->op) {
case nir_op_fadd:
break; /* This one's ok */
case nir_op_imov:
case nir_op_fmov:
case nir_op_fneg:
case nir_op_fabs:
assert(use_alu->dest.dest.is_ssa);
if (!are_all_uses_fadd(&use_alu->dest.dest.ssa))
return false;
break;
default:
return false;
}
}
return true;
}
static nir_alu_instr *
get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4], bool *negate, bool *abs)
{
@ -66,6 +101,12 @@ get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4], bool *negate, bool *abs)
break;
case nir_op_fmul:
/* Only absorbe a fmul into a ffma if the fmul is is only used in fadd
* operations. This prevents us from being too agressive with our
* fusing which can actually lead to more instructions.
*/
if (!are_all_uses_fadd(&alu->dest.dest.ssa))
return NULL;
break;
default: