On 08/13/2013 05:57 PM, Kenneth Graunke wrote:
On 08/13/2013 05:49 PM, Ian Romanick wrote:
On 08/13/2013 04:47 PM, Kenneth Graunke wrote:
Sandybridge is the only platform that supports an IF instruction
with an embedded comparison. In this case, we need to emit a CMP
to go along with the SEL.
Fixes regressions in Piglit's glsl-fs-atan-3, fs-unpackHalf2x16,
fs-faceforward-float-float-float, isinf-and-isnan fs_basic, and
isinf-and-isnan fs_fbo.
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index a36c248..984b08a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -1911,10 +1911,19 @@ fs_visitor::try_replace_with_sel()
emit(MOV(src0, then_mov->src[0]));
}
- fs_inst *sel = emit(BRW_OPCODE_SEL, then_mov->dst, src0,
else_mov->src[0]);
- sel->predicate = if_inst->predicate;
- sel->predicate_inverse = if_inst->predicate_inverse;
- sel->conditional_mod = if_inst->conditional_mod;
+ fs_inst *sel;
+ if (if_inst->conditional_mod) {
+ /* Sandybridge-specific IF with embedded comparison */
This doesn't appear to be SNB-specific code. Can you explain this? Is
if_inst->conditional_mod only set on SNB? I really need to learn more
about the back end...
Normally, control flow looks like:
cmp.l.f0(8) null g5<8,8,1>F 0F
(+f0) if(8)
For Sandybridge, the hardware designers extended IF to support built-in
comparisons, so you can simply do:
if.l(8) g5<8,8,1>F 0F
They immediately dropped this with Ivybridge; it's not been present on
any other platform.
fs_inst::conditional_mod represents that conditional modifier (always =
0, never, less, equal, lequal, greater, notequal, gequal).
In other words... yes to "Is if_inst->conditional_mod only set on SNB?" :)
Reviewed-by: Ian Romanick <ian.d.roman...@intel.com>
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