Delete metadata dx.disable_optimizations, if it exists,

from module after its presence has been noted in
ModuleMetadata Analysis pass. This ensures that this
metadata that is not part of DXIL specification
is not emitted in the final output.

Update disable-opt.ll to verify dx.disable_optimizations
metadata is deleted.

Author: bharadwajy

llvm/lib/Analysis/DXILMetadataAnalysis.cpp

@@ -71,17 +71,32 @@ static ModuleMetadataInfo collectMetadataInfo(Module &M) {
 
   // Set shader flags based on Module properties
   SmallVector<llvm::Module::ModuleFlagEntry> FlagEntries;
+  SmallVector<llvm::Module::ModuleFlagEntry> NewFlagEntries;
   M.getModuleFlagsMetadata(FlagEntries);
   for (const auto &Flag : FlagEntries) {
-    if (Flag.Behavior != Module::ModFlagBehavior::Override)
-      continue;
-    if (Flag.Key->getString().compare("dx.disable_optimizations") == 0) {
+    if ((Flag.Behavior == Module::ModFlagBehavior::Override) &&
+        (Flag.Key->getString().compare("dx.disable_optimizations") == 0)) {
       const auto *V = mdconst::extract<llvm::ConstantInt>(Flag.Val);
-      if (V->isOne()) {
+      if (V->isOne())
         MMDAI.DisableOptimizations = true;
-        break;
-      }
-    }
+    } else
+      // Collect all Module Flags other than dx.disable_optimizations.
+      NewFlagEntries.push_back(Flag);
+  }
+
+  // "dx.disable_optimizations" is not included in the metadata specified in
+  // DXIL specification. Hence it needs to be deleted such that it is not
+  // emitted in the final DXIL output, now that its intent is captured in MMDAI,
+  // if present.
+
+  if (NewFlagEntries.size() != FlagEntries.size()) {
+    NamedMDNode *OrigMDFlags = M.getModuleFlagsMetadata();
+    // Delete all Module flags
+    OrigMDFlags->eraseFromParent();
+    // Repopulate Module flags using the list that excludes
+    // dx.delete_optimizations.
+    for (const auto &Flag : NewFlagEntries)
+      M.addModuleFlag(Flag.Behavior, Flag.Key->getString(), Flag.Val);
   }
 
   return MMDAI;

llvm/test/CodeGen/DirectX/ShaderFlags/disable-opt.ll

@@ -18,8 +18,10 @@ entry:
   ret void
 }
 
+; CHECK-NOT: llvm.module.flags
 !llvm.module.flags = !{!0}
 
+; CHECK-NOT: "dx.disable_optimizations"
 !0 = !{i32 4, !"dx.disable_optimizations", i32 1}