CodeGen: Refactor regallocator command line and target selection

Make the sequence of passes to select and rewrite instructions to
physical registers be a target callback. This is to prepare to allow
targets to split register allocation into multiple phases.

include/llvm/CodeGen/TargetPassConfig.h

@@ -460,10 +460,10 @@ protected:
   /// regalloc pass.
   virtual FunctionPass *createRegAllocPass(bool Optimized);
 
-  /// Add core register alloator passes which do the actual register assignment
+  /// Add core register allocator passes which do the actual register assignment
   /// and rewriting. \returns true if any passes were added.
-  virtual bool addRegAssignmentFast();
+  virtual bool addRegAssignAndRewriteFast();
-  virtual bool addRegAssignmentOptimized();
+  virtual bool addRegAssignAndRewriteOptimized();
 };
 
 void registerCodeGenCallback(PassInstrumentationCallbacks &PIC,

lib/CodeGen/TargetPassConfig.cpp

@@ -1308,7 +1308,7 @@ FunctionPass *TargetPassConfig::createRegAllocPass(bool Optimized) {
   return createTargetRegisterAllocator(Optimized);
 }
 
-bool TargetPassConfig::addRegAssignmentFast() {
+bool TargetPassConfig::addRegAssignAndRewriteFast() {
   if (RegAlloc != &useDefaultRegisterAllocator &&
       RegAlloc != &createFastRegisterAllocator)
     report_fatal_error("Must use fast (default) register allocator for unoptimized regalloc.");
@@ -1317,7 +1317,7 @@ bool TargetPassConfig::addRegAssignmentFast() {
   return true;
 }
 
-bool TargetPassConfig::addRegAssignmentOptimized() {
+bool TargetPassConfig::addRegAssignAndRewriteOptimized() {
   // Add the selected register allocation pass.
   addPass(createRegAllocPass(true));
 
@@ -1327,12 +1327,6 @@ bool TargetPassConfig::addRegAssignmentOptimized() {
   // Finally rewrite virtual registers.
   addPass(&VirtRegRewriterID);
 
-  // Perform stack slot coloring and post-ra machine LICM.
-  //
-  // FIXME: Re-enable coloring with register when it's capable of adding
-  // kill markers.
-  addPass(&StackSlotColoringID);
-
   return true;
 }
 
@@ -1348,7 +1342,7 @@ void TargetPassConfig::addFastRegAlloc() {
   addPass(&PHIEliminationID, false);
   addPass(&TwoAddressInstructionPassID, false);
 
-  addRegAssignmentFast();
+  addRegAssignAndRewriteFast();
 }
 
 /// Add standard target-independent passes that are tightly coupled with
@@ -1391,7 +1385,13 @@ void TargetPassConfig::addOptimizedRegAlloc() {
   // PreRA instruction scheduling.
   addPass(&MachineSchedulerID);
 
-  if (addRegAssignmentOptimized()) {
+  if (addRegAssignAndRewriteOptimized()) {
+    // Perform stack slot coloring and post-ra machine LICM.
+    //
+    // FIXME: Re-enable coloring with register when it's capable of adding
+    // kill markers.
+    addPass(&StackSlotColoringID);
+
     // Allow targets to expand pseudo instructions depending on the choice of
     // registers before MachineCopyPropagation.
     addPostRewrite();

lib/Target/NVPTX/NVPTXTargetMachine.cpp

@@ -170,11 +170,11 @@ public:
   void addFastRegAlloc() override;
   void addOptimizedRegAlloc() override;
 
-  bool addRegAssignmentFast() override {
+  bool addRegAssignAndRewriteFast() override {
     llvm_unreachable("should not be used");
   }
 
-  bool addRegAssignmentOptimized() override {
+  bool addRegAssignAndRewriteOptimized() override {
     llvm_unreachable("should not be used");
   }
 

lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

@@ -326,10 +326,10 @@ public:
   void addPreEmitPass() override;
 
   // No reg alloc
-  bool addRegAssignmentFast() override { return false; }
+  bool addRegAssignAndRewriteFast() override { return false; }
 
   // No reg alloc
-  bool addRegAssignmentOptimized() override { return false; }
+  bool addRegAssignAndRewriteOptimized() override { return false; }
 };
 } // end anonymous namespace