[llvm] [DirectX] Strip `dx.rootsignatures` metadata during `dxil-prepare` (PR #145746)

[Finn Plummer via llvm-commits]

https://github.com/inbelic updated https://github.com/llvm/llvm-project/pull/145746

>From b862eea070494099621d09f40a30cf61963e3546 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 25 Jun 2025 17:03:31 +0000
Subject: [PATCH 1/4] remove dx.rootsignatures metadata and ensure dependent
 pass runs before

Co-authored-by: Justin Bogner "mail at justinbogner.com"
---
 llvm/lib/Target/DirectX/DXILPrepare.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/llvm/lib/Target/DirectX/DXILPrepare.cpp b/llvm/lib/Target/DirectX/DXILPrepare.cpp
index cb58f4833631d..c8866bfefdfc5 100644
--- a/llvm/lib/Target/DirectX/DXILPrepare.cpp
+++ b/llvm/lib/Target/DirectX/DXILPrepare.cpp
@@ -11,6 +11,7 @@
 /// Language (DXIL).
 //===----------------------------------------------------------------------===//
 
+#include "DXILRootSignature.h"
 #include "DXILShaderFlags.h"
 #include "DirectX.h"
 #include "DirectXIRPasses/PointerTypeAnalysis.h"
@@ -286,12 +287,21 @@ class DXILPrepareModule : public ModulePass {
     }
     // Remove flags not for DXIL.
     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();
+
     return true;
   }
 
   DXILPrepareModule() : ModulePass(ID) {}
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<DXILMetadataAnalysisWrapperPass>();
+    AU.addRequired<RootSignatureAnalysisWrapper>();
+    AU.addPreserved<RootSignatureAnalysisWrapper>();
     AU.addPreserved<ShaderFlagsAnalysisWrapper>();
     AU.addPreserved<DXILMetadataAnalysisWrapperPass>();
     AU.addPreserved<DXILResourceWrapperPass>();
@@ -305,6 +315,7 @@ char DXILPrepareModule::ID = 0;
 INITIALIZE_PASS_BEGIN(DXILPrepareModule, DEBUG_TYPE, "DXIL Prepare Module",
                       false, false)
 INITIALIZE_PASS_DEPENDENCY(DXILMetadataAnalysisWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(RootSignatureAnalysisWrapper)
 INITIALIZE_PASS_END(DXILPrepareModule, DEBUG_TYPE, "DXIL Prepare Module", false,
                     false)
 

>From 1fb6ff8f38767bb07c5b849ba6b7f6b2a8591bbf Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 25 Jun 2025 17:04:13 +0000
Subject: [PATCH 2/4] add test to ensure pass order is corrected

---
 llvm/test/CodeGen/DirectX/llc-pipeline.ll | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/test/CodeGen/DirectX/llc-pipeline.ll b/llvm/test/CodeGen/DirectX/llc-pipeline.ll
index 2b29fd30a7a56..5934de2c9758a 100644
--- a/llvm/test/CodeGen/DirectX/llc-pipeline.ll
+++ b/llvm/test/CodeGen/DirectX/llc-pipeline.ll
@@ -33,13 +33,13 @@
 ; CHECK-NEXT:   DXIL Translate Metadata
 ; CHECK-NEXT:   DXIL Post Optimization Validation
 ; CHECK-NEXT:   DXIL Op Lowering
+; CHECK-NEXT: DXIL Root Signature Analysis
 ; CHECK-NEXT:   DXIL Prepare Module
 
 ; CHECK-ASM-NEXT: DXIL Metadata Pretty Printer
 ; CHECK-ASM-NEXT: Print Module IR
 
 ; CHECK-OBJ-NEXT: DXIL Embedder
-; CHECK-OBJ-NEXT: DXIL Root Signature Analysis
 ; CHECK-OBJ-NEXT: DXContainer Global Emitter
 ; CHECK-OBJ-NEXT: FunctionPass Manager
 ; CHECK-OBJ-NEXT:   Lazy Machine Block Frequency Analysis

>From 4cce9453be5238c40b0300595d05b63683a69147 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 25 Jun 2025 17:32:12 +0000
Subject: [PATCH 3/4] add test to ensure the metadata is removed during
 dxil-prepare

---
 .../CodeGen/DirectX/strip-rootsignatures.ll     | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 llvm/test/CodeGen/DirectX/strip-rootsignatures.ll

diff --git a/llvm/test/CodeGen/DirectX/strip-rootsignatures.ll b/llvm/test/CodeGen/DirectX/strip-rootsignatures.ll
new file mode 100644
index 0000000000000..3b3ddf4886511
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/strip-rootsignatures.ll
@@ -0,0 +1,17 @@
+; RUN: opt -S -dxil-prepare < %s | FileCheck %s
+
+; Ensures that dxil-prepare will remove the dx.rootsignatures metadata
+
+target triple = "dxil-unknown-shadermodel6.0-compute"
+
+define void @main() {
+entry:
+  ret void
+}
+
+; CHECK-NOT: !dx.rootsignature
+
+!dx.rootsignatures = !{!2} ; list of function/root signature pairs
+!2 = !{ ptr @main, !3, i32 2 } ; function, root signature
+!3 = !{ !4 } ; list of root signature elements
+!4 = !{ !"RootFlags", i32 1 } ; 1 = allow_input_assembler_input_layout

>From c042e6f6d97b6c0c7158040b61ccadaa8985e81e Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 25 Jun 2025 17:44:38 +0000
Subject: [PATCH 4/4] review: fix typo

---
 llvm/test/CodeGen/DirectX/llc-pipeline.ll | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/test/CodeGen/DirectX/llc-pipeline.ll b/llvm/test/CodeGen/DirectX/llc-pipeline.ll
index 5934de2c9758a..36fed88fc52d6 100644
--- a/llvm/test/CodeGen/DirectX/llc-pipeline.ll
+++ b/llvm/test/CodeGen/DirectX/llc-pipeline.ll
@@ -33,7 +33,7 @@
 ; CHECK-NEXT:   DXIL Translate Metadata
 ; CHECK-NEXT:   DXIL Post Optimization Validation
 ; CHECK-NEXT:   DXIL Op Lowering
-; CHECK-NEXT: DXIL Root Signature Analysis
+; CHECK-NEXT:   DXIL Root Signature Analysis
 ; CHECK-NEXT:   DXIL Prepare Module
 
 ; CHECK-ASM-NEXT: DXIL Metadata Pretty Printer