[llvm] [DirectX] Use an allow-list of DXIL compatible module metadata (PR #165290)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-directx

Author: Finn Plummer (inbelic)

<details>
<summary>Changes</summary>

This pr introduces an allow-list for module metadata, this encompasses the llvm metadata nodes: `llvm.ident` and `llvm.module.flags`, as well as, the generated `dx.` options.

Resolves: #<!-- -->164473.

---
Full diff: https://github.com/llvm/llvm-project/pull/165290.diff


2 Files Affected:

- (modified) llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp (+21-13) 
- (added) llvm/test/CodeGen/DirectX/strip-module-md.ll (+75) 


``````````diff
diff --git a/llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp b/llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp
index 1e4797bbd05aa..be31da15581a3 100644
--- a/llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp
+++ b/llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp
@@ -364,6 +364,16 @@ static void cleanModuleFlags(Module &M) {
     M.addModuleFlag(Flag.Behavior, Flag.Key->getString(), Flag.Val);
 }
 
+using GlobalMDList = std::array<StringLiteral, 7>;
+
+// The following are compatible with DXIL but not emit with clang, they can
+// be added when applicable:
+// dx.typeAnnotations, dx.viewIDState, dx.dxrPayloadAnnotations
+static GlobalMDList CompatibleNamedModuleMDs = {
+    "llvm.ident",     "llvm.module.flags", "dx.resources",   "dx.valver",
+    "dx.shaderModel", "dx.version",        "dx.entryPoints",
+};
+
 static void translateGlobalMetadata(Module &M, DXILResourceMap &DRM,
                                     DXILResourceTypeMap &DRTM,
                                     const ModuleShaderFlags &ShaderFlags,
@@ -426,19 +436,17 @@ static void translateGlobalMetadata(Module &M, DXILResourceMap &DRM,
 
   cleanModuleFlags(M);
 
-  // dx.rootsignatures will have been parsed from its metadata form as its
-  // binary form as part of the RootSignatureAnalysisWrapper, so safely
-  // remove it as it is not recognized in DXIL
-  if (NamedMDNode *RootSignature = M.getNamedMetadata("dx.rootsignatures"))
-    RootSignature->eraseFromParent();
-
-  // llvm.errno.tbaa was recently added but is not supported in LLVM 3.7 and
-  // causes all tests using the DXIL Validator to fail.
-  //
-  // This is a temporary fix and should be replaced with a allowlist once
-  // we have determined all metadata that the DXIL Validator allows
-  if (NamedMDNode *ErrNo = M.getNamedMetadata("llvm.errno.tbaa"))
-    ErrNo->eraseFromParent();
+  // Finally, strip all module metadata that is not explicitly specified in the
+  // allow-list
+  SmallVector<NamedMDNode *> ToStrip;
+
+  for (NamedMDNode &NamedMD : M.named_metadata())
+    if (!NamedMD.getName().starts_with("llvm.dbg.") &&
+        !llvm::is_contained(CompatibleNamedModuleMDs, NamedMD.getName()))
+      ToStrip.push_back(&NamedMD);
+
+  for (NamedMDNode *NamedMD : ToStrip)
+    NamedMD->eraseFromParent();
 }
 
 PreservedAnalyses DXILTranslateMetadata::run(Module &M,
diff --git a/llvm/test/CodeGen/DirectX/strip-module-md.ll b/llvm/test/CodeGen/DirectX/strip-module-md.ll
new file mode 100644
index 0000000000000..4d8b9ec935f6b
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/strip-module-md.ll
@@ -0,0 +1,75 @@
+; RUN: opt -S -dxil-translate-metadata < %s | FileCheck %s
+
+; Ensures that only metadata explictly specified on the allow list, or debug
+; related, metadata is emitted
+
+target triple = "dxil-unknown-shadermodel6.0-compute"
+
+; CHECK-NOT: !dx.rootsignatures
+; CHECK-NOT: !llvm.errno.tbaa
+
+; CHECK-DAG: !llvm.dbg.cu
+
+; CHECK-DAG: !llvm.module.flags = !{![[#DWARF_VER:]], ![[#DEBUG_VER:]]}
+; CHECK-DAG: !llvm.ident = !{![[#IDENT:]]}
+
+; CHECK-DAG: !dx.shaderModel
+; CHECK-DAG: !dx.version
+; CHECK-DAG: !dx.entryPoints
+; CHECK-DAG: !dx.valver
+; CHECK-DAG: !dx.resources
+
+; CHECK-NOT: !dx.rootsignatures
+; CHECK-NOT: !llvm.errno.tbaa
+
+; Check allowed llvm metadata structure to ensure it is still DXIL compatible
+; If this fails, please ensure that the updated form is DXIL compatible before
+; updating the test.
+
+; CHECK-DAG: ![[#IDENT]] = !{!"clang 22.0.0"}
+; CHECK-DAG: ![[#DWARF_VER]] = !{i32 2, !"Dwarf Version", i32 2}
+; CHECK-DAG: ![[#DEBUG_VER]] = !{i32 2, !"Debug Info Version", i32 3}
+
+; CHECK-NOT: !dx.rootsignatures
+; CHECK-NOT: !llvm.errno.tbaa
+
+ at BufA.str = private unnamed_addr constant [5 x i8] c"BufA\00", align 1
+
+define void @main () #0 {
+entry:
+  %typed0 = call target("dx.TypedBuffer", <4 x float>, 1, 0, 0)
+              @llvm.dx.resource.handlefrombinding.tdx.TypedBuffer_v4f32_1_0_0(
+                  i32 3, i32 5, i32 1, i32 0, ptr @BufA.str)
+  ret void
+}
+
+attributes #0 = { noinline nounwind "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
+
+; Incompatible
+!dx.rootsignatures = !{!2}
+!llvm.errno.tbaa = !{!5}
+
+; Compatible
+!llvm.dbg.cu = !{!8}
+!llvm.module.flags = !{!11, !12}
+!llvm.ident = !{!13}
+!dx.valver = !{!14}
+
+!2 = !{ ptr @main, !3, i32 2 }
+!3 = !{ !4 }
+!4 = !{ !"RootFlags", i32 1 }
+
+!5 = !{!6, !6, i64 0}
+!6 = !{!"omnipotent char", !7}
+!7 = !{!"Simple C/C++ TBAA"}
+
+!8 = distinct !DICompileUnit(language: DW_LANG_C99, file: !9, producer: "Some Compiler", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !10, splitDebugInlining: false, nameTableKind: None)
+!9 = !DIFile(filename: "hlsl.hlsl", directory: "/some-path")
+!10 = !{}
+
+!11 = !{i32 2, !"Dwarf Version", i32 2}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+
+!13 = !{!"clang 22.0.0"}
+
+!14 = !{i32 1, i32 1}

``````````

</details>


https://github.com/llvm/llvm-project/pull/165290