AMDGPU: Disable some passes that are not meaningful

[arsenm]

Summary

Don't run passes related to stack maps, garbage collection,
exceptions since these aren't useful for GPUs.

There might be a few more to turn off that I'm less sure about
(e.g. ShrinkWrapping) or I'm not sure how to disable
(SafeStack and StackProtector)

[• tstellarAMD]

lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

300–303

Would it be better to disable the passes from the GCNPassConfig constructor?

LGTM.

[arsenm]

r248591

[arsenm]

lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

300–303

I moved it to the AMDGPUPassConfig constructor

lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

createMachineScheduler(MachineSchedContext *C) const override {
     const AMDGPUSubtarget &ST = *getAMDGPUTargetMachine().getSubtargetImpl();
     if (ST.getGeneration() <= AMDGPUSubtarget::NORTHERN_ISLANDS)
       return createR600MachineScheduler(C);
     return nullptr;
   }
 
   void addIRPasses() override;
   void addCodeGenPrepare() override;
-  virtual bool addPreISel() override;
-  virtual bool addInstSelector() override;
+  bool addPreISel() override;
+  bool addInstSelector() override;
+  bool addGCPasses() override;
 };
 
 class R600PassConfig : public AMDGPUPassConfig {
 public:
   R600PassConfig(TargetMachine *TM, PassManagerBase &PM)
     : AMDGPUPassConfig(TM, PM) { }
 
   bool addPreISel() override;
AMDGPUPassConfig::addPreISel() {
   return false;
 }
 
 bool AMDGPUPassConfig::addInstSelector() {
   addPass(createAMDGPUISelDag(getAMDGPUTargetMachine()));
   return false;
 }
 
+bool AMDGPUPassConfig::addGCPasses() {
+  // Do nothing. GC is not supported.
+  return false;
+}
+
 //===----------------------------------------------------------------------===//
 // R600 Pass Setup
 //===----------------------------------------------------------------------===//
 
 bool R600PassConfig::addPreISel() {
   AMDGPUPassConfig::addPreISel();
   addPass(createR600TextureIntrinsicsReplacer());
   return false;

 }
 
 void GCNPassConfig::addPreSched2() {
 }
 
 void GCNPassConfig::addPreEmitPass() {
   addPass(createSIInsertWaits(*TM), false);
   addPass(createSILowerControlFlowPass(*TM), false);
+
+  // Exceptions and StackMaps are not supported, so these passes will never do
+  // anything.
+  disablePass(&StackMapLivenessID);
+  disablePass(&FuncletLayoutID);
 }
 
 TargetPassConfig *GCNTargetMachine::createPassConfig(PassManagerBase &PM) {
   return new GCNPassConfig(this, PM);
 }