llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-directx
Author: Farzon Lotfi (farzonl)
<details>
<summary>Changes</summary>
fixes #<!-- -->135719
LLVM 3.7 did not have a freeze instruction
Further this instruction is really only used as syntactic sugar
in LLVM's optimizer passes to not aggressively optimize things
that could be undef or poison ie x*2 to x+x.
Most backends treat it as a no-op so we will do the same
by removing it and replacing its uses with its input.
---
Full diff: https://github.com/llvm/llvm-project/pull/136043.diff
2 Files Affected:
- (modified) llvm/lib/Target/DirectX/DXILLegalizePass.cpp (+14)
- (added) llvm/test/CodeGen/DirectX/legalize-freeze.ll (+17)
``````````diff
diff --git a/llvm/lib/Target/DirectX/DXILLegalizePass.cpp b/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
index 395311e430fbb..c133e59d2e3c6 100644
--- a/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
+++ b/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
@@ -8,6 +8,7 @@
#include "DXILLegalizePass.h"
#include "DirectX.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
@@ -20,6 +21,18 @@
using namespace llvm;
+static void legalizeFreeze(Instruction &I,
+ SmallVectorImpl<Instruction *> &ToRemove,
+ DenseMap<Value *, Value *>) {
+ auto *FI = dyn_cast<FreezeInst>(&I);
+ if (!FI)
+ return;
+
+ Value *Input = FI->getOperand(0);
+ FI->replaceAllUsesWith(Input);
+ ToRemove.push_back(FI);
+}
+
static void fixI8TruncUseChain(Instruction &I,
SmallVectorImpl<Instruction *> &ToRemove,
DenseMap<Value *, Value *> &ReplacedValues) {
@@ -169,6 +182,7 @@ class DXILLegalizationPipeline {
void initializeLegalizationPipeline() {
LegalizationPipeline.push_back(fixI8TruncUseChain);
LegalizationPipeline.push_back(downcastI64toI32InsertExtractElements);
+ LegalizationPipeline.push_back(legalizeFreeze);
}
};
diff --git a/llvm/test/CodeGen/DirectX/legalize-freeze.ll b/llvm/test/CodeGen/DirectX/legalize-freeze.ll
new file mode 100644
index 0000000000000..29446adeef215
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/legalize-freeze.ll
@@ -0,0 +1,17 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+
+; RUN: opt -S -passes='dxil-legalize' -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+
+define i32 @test_remove_freeze(i32 %x) {
+; CHECK-LABEL: define i32 @test_remove_freeze(
+; CHECK-SAME: i32 [[X:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[Y:%.*]] = add i32 [[X]], 1
+; CHECK-NEXT: ret i32 [[Y]]
+;
+entry:
+ %f = freeze i32 %x
+ %y = add i32 %f, 1
+ ret i32 %y
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/136043