[LegacyPM][DirectX] Add legacy scalarizer back for use in the DirectX backend (#107427)

As discussed in this
[proposal](https://github.com/llvm/wg-hlsl/pull/62/files?short_path=ac6e592#diff-ac6e59276afe8016e307eedc5c835f534c0cb353707760b44df0fa9d905a5cf8).
We had to bring back the legacy pass manager interface for the
scalarizer pass. Two reasons for this:
1. The DirectX backend is still using the legacy pass manager
2. The new PM isn't hooked up in clang yet via `BackendUtil.cpp`'s
`AddEmitPasses` That means even if we add a `buildCodeGenPipeline` we
won't be able to benefit from the new pass manager's scalarizer pass
interface.

The remaining changes are hooking up the scalarizer pass to the DirectX
backend, updating the DirectX test cases,
and allowing the `optdriver` to not block the legacy invocation of the
scalarizer pass.

Future work still needs to be done to allow the scalarizer pass to
handle target specific intrinsics.

closes #105178

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
index a29fc21..606022a9 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
@@ -28,6 +28,7 @@
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/LegacyPassManager.h"
+#include "llvm/InitializePasses.h"
 #include "llvm/MC/MCSectionDXContainer.h"
 #include "llvm/MC/SectionKind.h"
 #include "llvm/MC/TargetRegistry.h"
@@ -36,6 +37,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
+#include "llvm/Transforms/Scalar/Scalarizer.h"
 #include <optional>
 
 using namespace llvm;
@@ -44,6 +46,7 @@ extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeDirectXTarget() {
   RegisterTargetMachine<DirectXTargetMachine> X(getTheDirectXTarget());
   auto *PR = PassRegistry::getPassRegistry();
   initializeDXILIntrinsicExpansionLegacyPass(*PR);
+  initializeScalarizerLegacyPassPass(*PR);
   initializeDXILPrepareModulePass(*PR);
   initializeEmbedDXILPassPass(*PR);
   initializeWriteDXILPassPass(*PR);
@@ -83,6 +86,9 @@ public:
   FunctionPass *createTargetRegisterAllocator(bool) override { return nullptr; }
   void addCodeGenPrepare() override {
     addPass(createDXILIntrinsicExpansionLegacyPass());
+    ScalarizerPassOptions DxilScalarOptions;
+    DxilScalarOptions.ScalarizeLoadStore = true;
+    addPass(createScalarizerPass(DxilScalarOptions));
     addPass(createDXILOpLoweringLegacyPass());
     addPass(createDXILFinalizeLinkageLegacyPass());
     addPass(createDXILTranslateMetadataLegacyPass());