Mesa (master): i965: Optimize multiplication by -1 into a negated MOV.
Matt Turner
mattst88 at kemper.freedesktop.org
Sun Feb 15 20:24:52 UTC 2015
Module: Mesa
Branch: master
Commit: eb47d0efd39d73d4388389d6c0ebe458160f79fa
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=eb47d0efd39d73d4388389d6c0ebe458160f79fa
Author: Matt Turner <mattst88 at gmail.com>
Date: Wed Feb 4 18:08:30 2015 -0800
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 at intel.com>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 9 +++++++++
src/mesa/drivers/dri/i965/brw_vec4.cpp | 5 +++++
2 files changed, 14 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index c7c6acc..0f1300c 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -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;
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index fda8552..58828c3 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -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:
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