[globalisel][combine] Split existing rules into a match and apply step

Summary:
The declarative tablegen definitions split rules into match and apply steps.
Prepare for that by doing the same in the C++ implementations. This aids
some of the migration effort while the tablegen version is incomplete.

Reviewers: bogner, volkan, aditya_nandakumar, paquette, aemerson

Reviewed By: aditya_nandakumar

Subscribers: rovka, kristof.beyls, Petar.Avramovic, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58150

llvm-svn: 353996

include/llvm/CodeGen/GlobalISel/CombinerHelper.h

@@ -17,6 +17,8 @@
 #ifndef LLVM_CODEGEN_GLOBALISEL_COMBINER_HELPER_H
 #define LLVM_CODEGEN_GLOBALISEL_COMBINER_HELPER_H
 
+#include "llvm/CodeGen/LowLevelType.h"
+
 namespace llvm {
 
 class GISelChangeObserver;
@@ -25,6 +27,12 @@ class MachineRegisterInfo;
 class MachineInstr;
 class MachineOperand;
 
+struct PreferredTuple {
+  LLT Ty;                // The result type of the extend.
+  unsigned ExtendOpcode; // G_ANYEXT/G_SEXT/G_ZEXT
+  MachineInstr *MI;
+};
+
 class CombinerHelper {
   MachineIRBuilder &Builder;
   MachineRegisterInfo &MRI;
@@ -44,10 +52,14 @@ public:
   /// If \p MI is COPY, try to combine it.
   /// Returns true if MI changed.
   bool tryCombineCopy(MachineInstr &MI);
+  bool matchCombineCopy(MachineInstr &MI);
+  void applyCombineCopy(MachineInstr &MI);
 
   /// If \p MI is extend that consumes the result of a load, try to combine it.
   /// Returns true if MI changed.
   bool tryCombineExtendingLoads(MachineInstr &MI);
+  bool matchCombineExtendingLoads(MachineInstr &MI, PreferredTuple &MatchInfo);
+  void applyCombineExtendingLoads(MachineInstr &MI, PreferredTuple &MatchInfo);
 
   /// Try to transform \p MI by using all of the above
   /// combine functions. Returns true if changed.

lib/CodeGen/GlobalISel/CombinerHelper.cpp

@@ -46,6 +46,13 @@ void CombinerHelper::replaceRegOpWith(MachineRegisterInfo &MRI,
 }
 
 bool CombinerHelper::tryCombineCopy(MachineInstr &MI) {
+  if (matchCombineCopy(MI)) {
+    applyCombineCopy(MI);
+    return true;
+  }
+  return false;
+}
+bool CombinerHelper::matchCombineCopy(MachineInstr &MI) {
   if (MI.getOpcode() != TargetOpcode::COPY)
     return false;
   unsigned DstReg = MI.getOperand(0).getReg();
@@ -54,20 +61,18 @@ bool CombinerHelper::tryCombineCopy(MachineInstr &MI) {
   LLT SrcTy = MRI.getType(SrcReg);
   // Simple Copy Propagation.
   // a(sx) = COPY b(sx) -> Replace all uses of a with b.
-  if (DstTy.isValid() && SrcTy.isValid() && DstTy == SrcTy) {
-    MI.eraseFromParent();
-    replaceRegWith(MRI, DstReg, SrcReg);
+  if (DstTy.isValid() && SrcTy.isValid() && DstTy == SrcTy)
     return true;
-  }
   return false;
 }
+void CombinerHelper::applyCombineCopy(MachineInstr &MI) {
+  unsigned DstReg = MI.getOperand(0).getReg();
+  unsigned SrcReg = MI.getOperand(1).getReg();
+  MI.eraseFromParent();
+  replaceRegWith(MRI, DstReg, SrcReg);
+}
 
 namespace {
-struct PreferredTuple {
-  LLT Ty;                // The result type of the extend.
-  unsigned ExtendOpcode; // G_ANYEXT/G_SEXT/G_ZEXT
-  MachineInstr *MI;
-};
 
 /// Select a preference between two uses. CurrentUse is the current preference
 /// while *ForCandidate is attributes of the candidate under consideration.
@@ -152,16 +157,16 @@ static void InsertInsnsWithoutSideEffectsBeforeUse(
 } // end anonymous namespace
 
 bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) {
-  struct InsertionPoint {
-    MachineOperand *UseMO;
-    MachineBasicBlock *InsertIntoBB;
-    MachineBasicBlock::iterator InsertBefore;
-    InsertionPoint(MachineOperand *UseMO, MachineBasicBlock *InsertIntoBB,
-                   MachineBasicBlock::iterator InsertBefore)
-        : UseMO(UseMO), InsertIntoBB(InsertIntoBB), InsertBefore(InsertBefore) {
-    }
-  };
+  PreferredTuple Preferred;
+  if (matchCombineExtendingLoads(MI, Preferred)) {
+    applyCombineExtendingLoads(MI, Preferred);
+    return true;
+  }
+  return false;
+}
 
+bool CombinerHelper::matchCombineExtendingLoads(MachineInstr &MI,
+                                                PreferredTuple &Preferred) {
   // We match the loads and follow the uses to the extend instead of matching
   // the extends and following the def to the load. This is because the load
   // must remain in the same position for correctness (unless we also add code
@@ -199,7 +204,7 @@ bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) {
                                  : MI.getOpcode() == TargetOpcode::G_SEXTLOAD
                                        ? TargetOpcode::G_SEXT
                                        : TargetOpcode::G_ZEXT;
-  PreferredTuple Preferred = {LLT(), PreferredOpcode, nullptr};
+  Preferred = {LLT(), PreferredOpcode, nullptr};
   for (auto &UseMI : MRI.use_instructions(LoadValue.getReg())) {
     if (UseMI.getOpcode() == TargetOpcode::G_SEXT ||
         UseMI.getOpcode() == TargetOpcode::G_ZEXT ||
@@ -218,6 +223,20 @@ bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) {
   assert(Preferred.Ty != LoadValueTy && "Extending to same type?");
 
   LLVM_DEBUG(dbgs() << "Preferred use is: " << *Preferred.MI);
+  return true;
+}
+
+void CombinerHelper::applyCombineExtendingLoads(MachineInstr &MI,
+                                                PreferredTuple &Preferred) {
+  struct InsertionPoint {
+    MachineOperand *UseMO;
+    MachineBasicBlock *InsertIntoBB;
+    MachineBasicBlock::iterator InsertBefore;
+    InsertionPoint(MachineOperand *UseMO, MachineBasicBlock *InsertIntoBB,
+                   MachineBasicBlock::iterator InsertBefore)
+        : UseMO(UseMO), InsertIntoBB(InsertIntoBB), InsertBefore(InsertBefore) {
+    }
+  };
 
   // Rewrite the load to the chosen extending load.
   unsigned ChosenDstReg = Preferred.MI->getOperand(0).getReg();
@@ -232,6 +251,7 @@ bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) {
   // Rewrite all the uses to fix up the types.
   SmallVector<MachineInstr *, 1> ScheduleForErase;
   SmallVector<InsertionPoint, 4> ScheduleForInsert;
+  auto &LoadValue = MI.getOperand(0);
   for (auto &UseMO : MRI.use_operands(LoadValue.getReg())) {
     MachineInstr *UseMI = UseMO.getParent();
 
@@ -331,8 +351,6 @@ bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) {
   }
   MI.getOperand(0).setReg(ChosenDstReg);
   Observer.changedInstr(MI);
-
-  return true;
 }
 
 bool CombinerHelper::tryCombine(MachineInstr &MI) {