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i965: Optimize multiplication by -1 into a negated MOV. 

instructions in affected programs:     968 -> 942 (-2.69%)
helped:                                4

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Matt Turner 2015-02-04 18:08:30 -08:00
parent e8a6f2ad65
commit eb47d0efd3
2 changed files with 14 additions and 0 deletions
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9
src/mesa/drivers/dri/i965/brw_fs.cpp
View File

@ -2325,6 +2325,15 @@ fs_visitor::opt_algebraic()
break;
}
/* a * -1.0 = -a */
if (inst->src[1].is_negative_one()) {
inst->opcode = BRW_OPCODE_MOV;
inst->src[0].negate = !inst->src[0].negate;
inst->src[1] = reg_undef;
progress = true;
break;
}
/* a * 0.0 = 0.0 */
if (inst->src[1].is_zero()) {
inst->opcode = BRW_OPCODE_MOV;

5
src/mesa/drivers/dri/i965/brw_vec4.cpp
View File

@ -725,6 +725,11 @@ vec4_visitor::opt_algebraic()
inst->opcode = BRW_OPCODE_MOV;
inst->src[1] = src_reg();
progress = true;
} else if (inst->src[1].is_negative_one()) {
inst->opcode = BRW_OPCODE_MOV;
inst->src[0].negate = !inst->src[0].negate;
inst->src[1] = src_reg();
progress = true;
}
break;
case BRW_OPCODE_CMP: