Mesa (master): i965: Don' t dead-code eliminate instructions that write to the accumulator.
Matt Turner
mattst88 at kemper.freedesktop.org
Mon Oct 7 17:46:21 UTC 2013
Module: Mesa
Branch: master
Commit: 92dc16c3e2e2b9e3e71baaccc67bbe727e9d68ab
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=92dc16c3e2e2b9e3e71baaccc67bbe727e9d68ab
Author: Matt Turner <mattst88 at gmail.com>
Date: Thu Sep 19 19:31:31 2013 -0700
i965: Don't dead-code eliminate instructions that write to the accumulator.
Reviewed-by: Paul Berry <stereotype441 at gmail.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 16 +++++++++++++++-
src/mesa/drivers/dri/i965/brw_vec4.cpp | 16 +++++++++++++++-
2 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index b2c9f5a..b83aca4 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1846,7 +1846,21 @@ fs_visitor::dead_code_eliminate()
if (inst->dst.file == GRF) {
assert(this->virtual_grf_end[inst->dst.reg] >= pc);
if (this->virtual_grf_end[inst->dst.reg] == pc) {
- inst->remove();
+ /* Don't dead code eliminate instructions that write to the
+ * accumulator as a side-effect. Instead just set the destination
+ * to the null register to free it.
+ */
+ switch (inst->opcode) {
+ case BRW_OPCODE_ADDC:
+ case BRW_OPCODE_SUBB:
+ case BRW_OPCODE_MACH:
+ inst->dst.file = ARF;
+ inst->dst.reg = BRW_ARF_NULL;
+ break;
+ default:
+ inst->remove();
+ break;
+ }
progress = true;
}
}
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 75c3d34..790ff2e 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -314,7 +314,21 @@ vec4_visitor::dead_code_eliminate()
if (inst->dst.file == GRF) {
assert(this->virtual_grf_end[inst->dst.reg] >= pc);
if (this->virtual_grf_end[inst->dst.reg] == pc) {
- inst->remove();
+ /* Don't dead code eliminate instructions that write to the
+ * accumulator as a side-effect. Instead just set the destination
+ * to the null register to free it.
+ */
+ switch (inst->opcode) {
+ case BRW_OPCODE_ADDC:
+ case BRW_OPCODE_SUBB:
+ case BRW_OPCODE_MACH:
+ inst->dst.file = ARF;
+ inst->dst.reg = BRW_ARF_NULL;
+ break;
+ default:
+ inst->remove();
+ break;
+ }
progress = true;
}
}
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