[DirectX] Legalize llvm.lifetime.* intrinsics in EmbedDXILPass
#150100
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@llvm/pr-subscribers-backend-directx Author: Deric C. (Icohedron) ChangesFixes #147395 This PR:
Full diff: https://github.com/llvm/llvm-project/pull/150100.diff 4 Files Affected:
diff --git a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
index bd3349d2e18c5..eb4adfea5aed6 100644
--- a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
+++ b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
@@ -152,7 +152,7 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
if (!CSF.Int64Ops)
CSF.Int64Ops = I.getType()->isIntegerTy(64);
- if (!CSF.Int64Ops) {
+ if (!CSF.Int64Ops && !isa<LifetimeIntrinsic>(&I)) {
for (const Value *Op : I.operands()) {
if (Op->getType()->isIntegerTy(64)) {
CSF.Int64Ops = true;
diff --git a/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp b/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
index dfc79039cb54e..0ea1c5b905a45 100644
--- a/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
+++ b/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
@@ -17,6 +17,7 @@
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
@@ -52,6 +53,51 @@ class WriteDXILPass : public llvm::ModulePass {
}
};
+static void legalizeLifetimeIntrinsics(Module &M) {
+ for (Function &F : M) {
+ Intrinsic::ID IID = F.getIntrinsicID();
+ if (IID != Intrinsic::lifetime_start && IID != Intrinsic::lifetime_end)
+ continue;
+
+ // Lifetime intrinsics in LLVM 3.7 do not have the memory FnAttr
+ F.removeFnAttr(Attribute::Memory);
+
+ // Lifetime intrinsics in LLVM 3.7 do not have mangled names
+ F.setName(Intrinsic::getBaseName(IID));
+
+ // LLVM 3.7 Lifetime intrinics require an i8* operand, so we insert bitcasts
+ // to ensure that is the case
+ for (auto *User : make_early_inc_range(F.users())) {
+ CallInst *CI = dyn_cast<CallInst>(User);
+ assert(CI && "Expected user of a lifetime intrinsic function to be a "
+ "lifetime intrinsic call");
+ Value *PtrOperand = CI->getArgOperand(1);
+ PointerType *PtrTy = cast<PointerType>(PtrOperand->getType());
+ Value *NoOpBitCast = CastInst::Create(Instruction::BitCast, PtrOperand,
+ PtrTy, "", CI->getIterator());
+ CI->setArgOperand(1, NoOpBitCast);
+ }
+ }
+}
+
+static void removeLifetimeIntrinsics(Module &M) {
+ for (Function &F : make_early_inc_range(M))
+ if (Intrinsic::ID IID = F.getIntrinsicID();
+ IID == Intrinsic::lifetime_start || IID == Intrinsic::lifetime_end) {
+ for (User *U : make_early_inc_range(F.users())) {
+ LifetimeIntrinsic *LI = dyn_cast<LifetimeIntrinsic>(U);
+ assert(LI && "Expected user of lifetime intrinsic function to be "
+ "a LifetimeIntrinsic instruction");
+ BitCastInst *BCI = dyn_cast<BitCastInst>(LI->getArgOperand(1));
+ assert(BCI && "Expected pointer operand of LifetimeIntrinsic to be a "
+ "BitCastInst");
+ LI->eraseFromParent();
+ BCI->eraseFromParent();
+ }
+ F.eraseFromParent();
+ }
+}
+
class EmbedDXILPass : public llvm::ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
@@ -70,8 +116,17 @@ class EmbedDXILPass : public llvm::ModulePass {
// Only the output bitcode need to be DXIL triple.
M.setTargetTriple(Triple("dxil-ms-dx"));
+ // Perform late legalization of lifetime intrinsics that would otherwise
+ // fail the Module Verifier if performed in an earlier pass
+ legalizeLifetimeIntrinsics(M);
+
WriteDXILToFile(M, OS);
+ // We no longer need lifetime intrinsics after bitcode serialization, so we
+ // simply remove them to keep the Module Verifier happy after our
+ // not-so-legal legalizations
+ removeLifetimeIntrinsics(M);
+
// Recover triple.
M.setTargetTriple(OriginalTriple);
diff --git a/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll b/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
new file mode 100644
index 0000000000000..736c86ebb1299
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
@@ -0,0 +1,36 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+; RUN: llc %s --filetype=obj -o - | obj2yaml | FileCheck %s --check-prefix=DXC
+
+target triple = "dxil-pc-shadermodel6.7-library"
+
+; CHECK: ; Combined Shader Flags for Module
+; CHECK-NEXT: ; Shader Flags Value: 0x00000000
+; CHECK-NEXT: ;
+; CHECK-NOT: ; Note: shader requires additional functionality:
+; CHECK-NOT: ; 64-Bit integer
+; CHECK-NOT: ; Note: extra DXIL module flags:
+; CHECK-NOT: ;
+; CHECK-NEXT: ; Shader Flags for Module Functions
+; CHECK-NEXT: ; Function lifetimes : 0x00000000
+
+define void @lifetimes() #0 {
+ %a = alloca [4 x i32], align 8
+ call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %a)
+ call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %a)
+ ret void
+}
+
+; Function Attrs: nounwind memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(i64, ptr) #1
+
+; Function Attrs: nounwind memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(i64, ptr) #1
+
+attributes #0 = { convergent norecurse nounwind "hlsl.export"}
+attributes #1 = { nounwind memory(argmem: readwrite) }
+
+; DXC: - Name: SFI0
+; DXC-NEXT: Size: 8
+; DXC-NOT: Flags:
+; DXC-NOT: Int64Ops: true
+; DXC: ...
diff --git a/llvm/test/tools/dxil-dis/lifetimes.ll b/llvm/test/tools/dxil-dis/lifetimes.ll
new file mode 100644
index 0000000000000..cb3e6291c7bc0
--- /dev/null
+++ b/llvm/test/tools/dxil-dis/lifetimes.ll
@@ -0,0 +1,38 @@
+; RUN: llc --filetype=obj %s -o - | dxil-dis -o - | FileCheck %s
+target triple = "dxil-unknown-shadermodel6.7-library"
+
+define void @test_lifetimes() {
+; CHECK-LABEL: test_lifetimes
+; CHECK-NEXT: [[ALLOCA:%.*]] = alloca [2 x i32], align 4
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr [2 x i32], [2 x i32]* [[ALLOCA]], i32 0, i32 0
+; CHECK-NEXT: [[BITCAST:%.*]] = bitcast [2 x i32]* [[ALLOCA]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start(i64 4, i8* nonnull [[BITCAST]])
+; CHECK-NEXT: store i32 0, i32* [[GEP]], align 4
+; CHECK-NEXT: [[BITCAST:%.*]] = bitcast [2 x i32]* [[ALLOCA]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.end(i64 4, i8* nonnull [[BITCAST]])
+; CHECK-NEXT: ret void
+;
+ %a = alloca [2 x i32], align 4
+ %gep = getelementptr [2 x i32], ptr %a, i32 0, i32 0
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %a)
+ store i32 0, ptr %gep, align 4
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %a)
+ ret void
+}
+
+; CHECK-DAG: attributes [[LIFETIME_ATTRS:#.*]] = { nounwind }
+
+; CHECK-DAG: ; Function Attrs: nounwind
+; CHECK-DAG: declare void @llvm.lifetime.start(i64, i8* nocapture) [[LIFETIME_ATTRS]]
+
+; CHECK-DAG: ; Function Attrs: nounwind
+; CHECK-DAG: declare void @llvm.lifetime.end(i64, i8* nocapture) [[LIFETIME_ATTRS]]
+
+; Function Attrs: nounwind memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(i64, ptr) #0
+
+; Function Attrs: nounwind memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(i64, ptr) #0
+
+attributes #0 = { nounwind memory(argmem: readwrite) }
+
|
bob80905
reviewed
Jul 22, 2025
|
Is it possible to add a test so that we see the lifetime intrinsics / bitcasts getting removed, along with the lifetime function declaration? Perhaps by using a CHECK-NOT? |
llvm-beanz
reviewed
Jul 22, 2025
Comment on lines
85
to
86
| if (Intrinsic::ID IID = F.getIntrinsicID(); | ||
| IID == Intrinsic::lifetime_start || IID == Intrinsic::lifetime_end) { |
There was a problem hiding this comment.
nit: I'd usually recommend inverting the condition and having a continue here instead of nesting further. That matches what you did above and aligns with the coding standards.
https://llvm.org/docs/CodingStandards.html#use-early-exits-and-continue-to-simplify-code
llvm-beanz
approved these changes
Jul 22, 2025
You can test this locally with the following command:git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 'HEAD~1' HEAD llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll llvm/test/tools/dxil-dis/lifetimes.ll llvm/lib/Target/DirectX/DXILShaderFlags.cpp llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.llThe following files introduce new uses of undef:
Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields In tests, avoid using For example, this is considered a bad practice: define void @fn() {
...
br i1 undef, ...
}Please use the following instead: define void @fn(i1 %cond) {
...
br i1 %cond, ...
}Please refer to the Undefined Behavior Manual for more information. |
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Fixes #147395
This PR:
llvm.lifetime.*intrinsics in the EmbedDXILPass just before invoking the DXILBitcodeWriter.