[DirectX] Flatten arrays (#114332)

-  Relevant piece is `DXILFlattenArrays.cpp`
- Loads and Store Instruction visits are just for finding
GetElementPtrConstantExpr and splitting them.
-  Allocas needed to be replaced with flattened allocas.
- Global arrays were similar to allocas. Only interesting piece here is
around initializers.
- Most of the work went into building correct GEP chains. The approach
here was a recursive strategy via `recursivelyCollectGEPs`.
- All intermediary GEPs get marked for deletion and only the leaf GEPs
get updated with the new index.

fixes [89646](https://github.com/llvm/llvm-project/issues/89646)

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
index 18251ea..59dbf05 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
@@ -13,6 +13,7 @@
 
 #include "DirectXTargetMachine.h"
 #include "DXILDataScalarization.h"
+#include "DXILFlattenArrays.h"
 #include "DXILIntrinsicExpansion.h"
 #include "DXILOpLowering.h"
 #include "DXILPrettyPrinter.h"
@@ -48,6 +49,7 @@ extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeDirectXTarget() {
   auto *PR = PassRegistry::getPassRegistry();
   initializeDXILIntrinsicExpansionLegacyPass(*PR);
   initializeDXILDataScalarizationLegacyPass(*PR);
+  initializeDXILFlattenArraysLegacyPass(*PR);
   initializeScalarizerLegacyPassPass(*PR);
   initializeDXILPrepareModulePass(*PR);
   initializeEmbedDXILPassPass(*PR);
@@ -91,6 +93,7 @@ public:
     addPass(createDXILDataScalarizationLegacyPass());
     ScalarizerPassOptions DxilScalarOptions;
     DxilScalarOptions.ScalarizeLoadStore = true;
+    addPass(createDXILFlattenArraysLegacyPass());
     addPass(createScalarizerPass(DxilScalarOptions));
     addPass(createDXILOpLoweringLegacyPass());
     addPass(createDXILFinalizeLinkageLegacyPass());