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[DXIL] Remove incompatible metadata types when preparing DXIL. #136386

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Merged
merged 8 commits into from
Apr 28, 2025
Merged

[DXIL] Remove incompatible metadata types when preparing DXIL. #136386

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c1a89d6
add md node type filter, and test
bob80905 Apr 18, 2025
0399c6f
add dxil prepare pass
bob80905 Apr 24, 2025
19de155
remove hlsl file
bob80905 Apr 24, 2025
416084c
drop tbaa and memparallelloopaccess, add 3 dx mds, simplify test
bob80905 Apr 25, 2025
84ad1d4
prune whitelist
bob80905 Apr 25, 2025
fb2932e
address Justin
bob80905 Apr 25, 2025
b18f093
remove nonuniform test, patternmatch vars, simplify test description
bob80905 Apr 28, 2025
58683b6
address Justin
bob80905 Apr 28, 2025
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15 changes: 15 additions & 0 deletions llvm/lib/Target/DirectX/DXILPrepare.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,15 @@ class DXILPrepareModule : public ModulePass {
Builder.getPtrTy(PtrTy->getAddressSpace())));
}

static std::array<unsigned, 6> getCompatibleInstructionMDs(llvm::Module &M) {
return {M.getMDKindID("dx.nonuniform"),
M.getMDKindID("dx.controlflow.hints"),
M.getMDKindID("dx.precise"),
llvm::LLVMContext::MD_range,
llvm::LLVMContext::MD_alias_scope,
llvm::LLVMContext::MD_noalias};
}

public:
bool runOnModule(Module &M) override {
PointerTypeMap PointerTypes = PointerTypeAnalysis::run(M);
Expand All @@ -176,6 +185,9 @@ class DXILPrepareModule : public ModulePass {
VersionTuple ValVer = MetadataInfo.ValidatorVersion;
bool SkipValidation = ValVer.getMajor() == 0 && ValVer.getMinor() == 0;

// construct whitelist of valid metadata node kinds
std::array<unsigned, 6> DXILCompatibleMDs = getCompatibleInstructionMDs(M);

for (auto &F : M.functions()) {
F.removeFnAttrs(AttrMask);
F.removeRetAttrs(AttrMask);
Expand All @@ -189,6 +201,9 @@ class DXILPrepareModule : public ModulePass {
for (auto &BB : F) {
IRBuilder<> Builder(&BB);
for (auto &I : make_early_inc_range(BB)) {

I.dropUnknownNonDebugMetadata(DXILCompatibleMDs);

if (I.getOpcode() == Instruction::FNeg) {
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DXILPrepare has a bunch of overlap with the legalization pass. Seems like MetaData might not be able to move because legalization is a function level pass and this is a module level one, but at a minimum it seems like FNeg -> FSub should move.

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I agree. I think DXILPrepare should do things like translate attributes and metadata, insert no-op bitcasts to appease the bitcode writer, and that sort of thing. Replacing ops with their equivalents should squarely be a part of legalization, not here.

I've filed #137685

Builder.SetInsertPoint(&I);
Value *In = I.getOperand(0);
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29 changes: 29 additions & 0 deletions llvm/test/CodeGen/DirectX/metadata-stripping.ll
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@@ -0,0 +1,29 @@
; RUN: opt -S --dxil-prepare %s | FileCheck %s

; Test that only metadata nodes that are valid in DXIL are allowed through

target triple = "dxilv1.0-unknown-shadermodel6.0-compute"

; Function Attrs: noinline nounwind memory(readwrite, inaccessiblemem: none)
define void @main(i32* %ptr) {
entry:
; metadata ID changes to 0 once the current !0 and !1 are removed
; since they aren't in the whitelist. range needs a payload.
; CHECK: %val = load i32, ptr %ptr, align 4, !range [[RANGEMD:![0-9]+]]
%val = load i32, ptr %ptr, align 4, !range !2

%cmp.i = icmp ult i32 1, 2
br i1 %cmp.i, label %_Z4mainDv3_j.exit, label %_Z4mainDv3_j.exit, !llvm.loop !0

_Z4mainDv3_j.exit: ; preds = %for.body.i, %entry
ret void
}

; CHECK: [[RANGEMD]] = !{i32 1, i32 5}
; this next check line checks that nothing comes after the above check line.
; No more metadata should be necessary, the rest (the current 0 and 1)
; should be removed.
; CHECK-NOT: !{!"llvm.loop.mustprogress"}
!0 = distinct !{!0, !1}
!1 = !{!"llvm.loop.mustprogress"}
!2 = !{i32 1, i32 5}
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