add md node type filter, and test

Author: bob80905

clang/test/CodeGenHLSL/metadata-stripping.hlsl

@@ -0,0 +1,13 @@
+// RUN: %clang --driver-mode=dxc -T cs_6_0 -Fo x.dxil %s | FileCheck %s
+// CHECK-NOT: llvm.loop.mustprogress
+
+StructuredBuffer<uint4> X : register(t0);
+StructuredBuffer<float4> In : register(t1);
+RWStructuredBuffer<float4> Out : register(u0);
+
+[numthreads(1, 1, 1)]
+void main(uint3 dispatch_thread_id : SV_DispatchThreadID) {
+  for (uint I = 0; I < X[dispatch_thread_id].x; ++I) {
+    Out[dispatch_thread_id] = In[dispatch_thread_id];
+  }
+}

llvm/lib/Target/DirectX/DXILPrepare.cpp

@@ -189,6 +189,26 @@ class DXILPrepareModule : public ModulePass {
       for (auto &BB : F) {
         IRBuilder<> Builder(&BB);
         for (auto &I : make_early_inc_range(BB)) {
+
+          // TODO: Audit this list - is it enough? Too much?
+          static unsigned DXILCompatibleMDs[] = {
+              LLVMContext::MD_dbg,
+              LLVMContext::MD_tbaa,
+              LLVMContext::MD_prof,
+              LLVMContext::MD_fpmath,
+              LLVMContext::MD_range,
+              LLVMContext::MD_tbaa_struct,
+              LLVMContext::MD_invariant_load,
+              LLVMContext::MD_alias_scope,
+              LLVMContext::MD_noalias,
+              LLVMContext::MD_nontemporal,
+              LLVMContext::MD_mem_parallel_loop_access,
+              LLVMContext::MD_nonnull,
+              LLVMContext::MD_dereferenceable,
+              LLVMContext::MD_dereferenceable_or_null,
+          };
+          I.dropUnknownNonDebugMetadata(DXILCompatibleMDs);
+
           if (I.getOpcode() == Instruction::FNeg) {
             Builder.SetInsertPoint(&I);
             Value *In = I.getOperand(0);