[AMDGPU] Port AMDGPURewriteUndefForPHI to new pass manager

This patch ports the AMDGPURewriteUndefForPHI pass to the new pass
manager. With this, the pass is supported under both the legacy and
the new pass managers.

Author: Jun Wang

llvm/lib/Target/AMDGPU/AMDGPU.h

@@ -291,6 +291,16 @@ FunctionPass *createAMDGPURewriteUndefForPHIPass();
 void initializeAMDGPURewriteUndefForPHIPass(PassRegistry &);
 extern char &AMDGPURewriteUndefForPHIPassID;
 
+class AMDGPURewriteUndefForPHIPass
+    : public PassInfoMixin<AMDGPURewriteUndefForPHIPass> {
+private:
+  TargetMachine &TM;
+
+public:
+  AMDGPURewriteUndefForPHIPass(TargetMachine &TM) : TM(TM){};
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
 void initializeSIAnnotateControlFlowPass(PassRegistry&);
 extern char &SIAnnotateControlFlowPassID;
 

llvm/lib/Target/AMDGPU/AMDGPURewriteUndefForPHI.cpp

@@ -177,6 +177,20 @@ bool AMDGPURewriteUndefForPHI::runOnFunction(Function &F) {
   return rewritePHIs(F, UA, DT);
 }
 
+PreservedAnalyses
+AMDGPURewriteUndefForPHIPass::run(Function &F, FunctionAnalysisManager &AM) {
+  UniformityInfo &UA = AM.getResult<UniformityInfoAnalysis>(F);
+  DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
+  bool Changed = rewritePHIs(F, UA, DT);
+  if (Changed) {
+    PreservedAnalyses PA;
+    PA.preserveSet<CFGAnalyses>();
+    return PA;
+  }
+
+  return PreservedAnalyses::all();
+}
+
 FunctionPass *llvm::createAMDGPURewriteUndefForPHIPass() {
   return new AMDGPURewriteUndefForPHI();
 }

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -663,6 +663,10 @@ void AMDGPUTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
           PM.addPass(AMDGPULowerKernelArgumentsPass(*this));
           return true;
         }
+        if (PassName == "amdgpu-rewrite-undef-for-phi") {
+          PM.addPass(AMDGPURewriteUndefForPHIPass(*this));
+          return true;
+        }
         return false;
       });
 

llvm/test/CodeGen/AMDGPU/rewrite-undef-for-phi.ll

@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -mtriple=amdgcn-- -S -amdgpu-rewrite-undef-for-phi %s | FileCheck -check-prefix=OPT %s
+; RUN: opt -mtriple=amdgcn-- -S -passes=amdgpu-rewrite-undef-for-phi %s | FileCheck -check-prefix=OPT %s
 
 define amdgpu_ps float @basic(float inreg %c, i32 %x) #0 {
 ; OPT-LABEL: @basic(