Mesa (master): ac: reassociate FP expressions for inexact instructions for radeonsi

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Module: Mesa
Branch: master
Commit: cf2f3c27533d8721abed4cdd4dfb00d4d53e8a0f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=cf2f3c27533d8721abed4cdd4dfb00d4d53e8a0f

Author: Marek Olšák <marek.olsak at amd.com>
Date:   Wed Apr 22 23:01:28 2020 -0400

ac: reassociate FP expressions for inexact instructions for radeonsi

Totals:
SGPRS: 2591784 -> 2590696 (-0.04 %)
VGPRS: 1666888 -> 1666736 (-0.01 %)
Spilled SGPRs: 4131 -> 4107 (-0.58 %)
Spilled VGPRs: 38 -> 38 (0.00 %)
Private memory VGPRs: 2176 -> 2176 (0.00 %)
Scratch size: 2228 -> 2228 (0.00 %) dwords per thread
Code Size: 52715468 -> 52693584 (-0.04 %) bytes
LDS: 92 -> 92 (0.00 %) blocks
Max Waves: 479897 -> 479892 (-0.00 %)
Wait states: 0 -> 0 (0.00 %)

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4696>

---

 src/amd/llvm/ac_llvm_helper.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/amd/llvm/ac_llvm_helper.cpp b/src/amd/llvm/ac_llvm_helper.cpp
index f5383344dd4..97b9a1a035a 100644
--- a/src/amd/llvm/ac_llvm_helper.cpp
+++ b/src/amd/llvm/ac_llvm_helper.cpp
@@ -101,6 +101,11 @@ LLVMBuilderRef ac_create_builder(LLVMContextRef ctx,
 		 */
 		flags.setAllowContract(); /* contract */
 
+		/* Allow reassociation transformations for floating-point
+		 * instructions. This may dramatically change results.
+		 */
+		flags.setAllowReassoc(); /* reassoc */
+
 		llvm::unwrap(builder)->setFastMathFlags(flags);
 		break;
 	}
@@ -113,11 +118,13 @@ bool ac_disable_inexact_math(LLVMBuilderRef builder)
 {
 	auto *b = llvm::unwrap(builder);
 	llvm::FastMathFlags flags = b->getFastMathFlags();
+	assert(flags.allowContract() == flags.allowReassoc());
 
 	if (!flags.allowContract())
 		return false;
 
 	flags.setAllowContract(false);
+	flags.setAllowReassoc(false);
 	b->setFastMathFlags(flags);
 	return true;
 }
@@ -126,11 +133,13 @@ void ac_restore_inexact_math(LLVMBuilderRef builder, bool value)
 {
 	auto *b = llvm::unwrap(builder);
 	llvm::FastMathFlags flags = b->getFastMathFlags();
+	assert(flags.allowContract() == flags.allowReassoc());
 
 	if (flags.allowContract() == value)
 		return;
 
 	flags.setAllowContract(value);
+	flags.setAllowReassoc(value);
 	b->setFastMathFlags(flags);
 }