AMDGPU/NewPM: Start implementing addCodeGenPrepare

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPUCodeGenPassBuilder.cpp

@@ -19,6 +19,7 @@
 #include "llvm/Transforms/Scalar/StructurizeCFG.h"
 #include "llvm/Transforms/Utils/FixIrreducible.h"
 #include "llvm/Transforms/Utils/LCSSA.h"
+#include "llvm/Transforms/Utils/LowerSwitch.h"
 #include "llvm/Transforms/Utils/UnifyLoopExits.h"
 
 using namespace llvm;
@@ -35,6 +36,16 @@ AMDGPUCodeGenPassBuilder::AMDGPUCodeGenPassBuilder(
               ShadowStackGCLoweringPass>();
 }
 
+void AMDGPUCodeGenPassBuilder::addCodeGenPrepare(AddIRPass &addPass) const {
+  Base::addCodeGenPrepare(addPass);
+
+  // LowerSwitch pass may introduce unreachable blocks that can cause unexpected
+  // behavior for subsequent passes. Placing it here seems better that these
+  // blocks would get cleaned up by UnreachableBlockElim inserted next in the
+  // pass flow.
+  addPass(LowerSwitchPass());
+}
+
 void AMDGPUCodeGenPassBuilder::addPreISel(AddIRPass &addPass) const {
   const bool LateCFGStructurize = AMDGPUTargetMachine::EnableLateStructurizeCFG;
   const bool DisableStructurizer = AMDGPUTargetMachine::DisableStructurizer;

llvm/lib/Target/AMDGPU/AMDGPUCodeGenPassBuilder.h

@@ -19,10 +19,12 @@ class GCNTargetMachine;
 class AMDGPUCodeGenPassBuilder
     : public CodeGenPassBuilder<AMDGPUCodeGenPassBuilder, GCNTargetMachine> {
 public:
+  using Base = CodeGenPassBuilder<AMDGPUCodeGenPassBuilder, GCNTargetMachine>;
+
   AMDGPUCodeGenPassBuilder(GCNTargetMachine &TM,
                            const CGPassBuilderOption &Opts,
                            PassInstrumentationCallbacks *PIC);
-
+  void addCodeGenPrepare(AddIRPass &) const;
   void addPreISel(AddIRPass &addPass) const;
   void addAsmPrinter(AddMachinePass &, CreateMCStreamer) const;
   Error addInstSelector(AddMachinePass &) const;

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -67,6 +67,7 @@
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/InferAddressSpaces.h"
 #include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/LowerSwitch.h"
 #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
 #include "llvm/Transforms/Vectorize/LoadStoreVectorizer.h"
 #include <optional>