[DirectX] remove unrecognized 'llvm.errno.tbaa' named metadata for DXIL target (llvm#164472)

This is a temporary measure to explicitly remove the unrecognized named
metadata when targeting DXIL.

This should be removed for an allowlist as tracked here:
llvm#164473.

Author: inbelic

llvm/lib/Target/DirectX/DXILPrepare.cpp

@@ -294,6 +294,14 @@ class DXILPrepareModule : public ModulePass {
     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 whitelist once
+    // we have determined all metadata that the DXIL Validator allows
+    if (NamedMDNode *ErrNo = M.getNamedMetadata("llvm.errno.tbaa"))
+      ErrNo->eraseFromParent();
+
     return true;
   }
 

llvm/test/CodeGen/DirectX/strip-llvm-errno-tbaa.ll

@@ -0,0 +1,19 @@
+; RUN: opt -S -dxil-prepare < %s | FileCheck %s
+
+; Ensures that dxil-prepare will remove the llvm.errno.tbaa metadata
+
+target triple = "dxil-unknown-shadermodel6.0-compute"
+
+define void @main() {
+entry:
+  ret void
+}
+
+; CHECK-NOT: !llvm.errno.tbaa
+; CHECK-NOT: {{^!}}
+
+!llvm.errno.tbaa = !{!0}
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"omnipotent char", !2}
+!2 = !{!"Simple C/C++ TBAA"}