Mesa (master): i965/vec4: Fix dead code elimination for VGRFs of size > 1.
Kenneth Graunke
kwg at kemper.freedesktop.org
Sun Jun 15 23:50:02 UTC 2014
Module: Mesa
Branch: master
Commit: d0575d98fc595dcc17706dc73d1eb461027ca17a
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=d0575d98fc595dcc17706dc73d1eb461027ca17a
Author: Kenneth Graunke <kenneth at whitecape.org>
Date: Sat Jun 14 03:53:07 2014 -0700
i965/vec4: Fix dead code elimination for VGRFs of size > 1.
When faced with code such as:
mov vgrf31.0:UD, 960D
mov vgrf31.1:UD, vgrf30.xxxx:UD
The dead code eliminator didn't consider reg_offsets, so it decided that
the second instruction was writing was writing to the same register as
the first one, and eliminated the first one. But they're actually
different registers.
This fixes INTEL_DEBUG=shader_time for vertex shaders. In the above
code, vgrf31.0 represents the offset into the shader_time buffer where
the data should be written, and vgrf31.1 represents the actual time
data. With a completely undefined offset, results were...unexpected.
I think this is probably one of the few cases (maybe only case) where we
generate multiple MOVs to a large VGRF. Normally, we just use them as
texturing results; the other SEND-from-GRF uses a size 1 VGRF.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79029
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Cc: mesa-stable at lists.freedesktop.org
---
src/mesa/drivers/dri/i965/brw_vec4.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index e816b94..ee5be56 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -464,7 +464,8 @@ vec4_visitor::dead_code_eliminate()
}
if (inst->dst.file == scan_inst->dst.file &&
- inst->dst.reg == scan_inst->dst.reg) {
+ inst->dst.reg == scan_inst->dst.reg &&
+ inst->dst.reg_offset == scan_inst->dst.reg_offset) {
int new_writemask = scan_inst->dst.writemask & ~dead_channels;
progress = try_eliminate_instruction(scan_inst, new_writemask, brw) ||
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