[GlobalISel] Refactor Legalizer helpers for libcalls

We used to have a helper that replaced an instruction with a libcall.
That turns out to be too aggressive, since sometimes we need to replace
the instruction with at least two libcalls. Therefore, change our
existing helper to only create the libcall and leave the instruction
removal as a separate step. Also rename the helper accordingly.

llvm-svn: 307149

1 files changed, 20 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 84b0a0ac415..6b3c5249db1 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -99,23 +99,17 @@ static RTLIB::Libcall getRTLibDesc(unsigned Opcode, unsigned Size) {
   llvm_unreachable("Unknown libcall function");
 }
 
-LegalizerHelper::LegalizeResult llvm::replaceWithLibcall(
-    MachineInstr &MI, MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
-    const CallLowering::ArgInfo &Result, ArrayRef<CallLowering::ArgInfo> Args) {
+LegalizerHelper::LegalizeResult
+llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
+                    const CallLowering::ArgInfo &Result,
+                    ArrayRef<CallLowering::ArgInfo> Args) {
   auto &CLI = *MIRBuilder.getMF().getSubtarget().getCallLowering();
   auto &TLI = *MIRBuilder.getMF().getSubtarget().getTargetLowering();
   const char *Name = TLI.getLibcallName(Libcall);
   MIRBuilder.getMF().getFrameInfo().setHasCalls(true);
-  MIRBuilder.setInstr(MI);
   if (!CLI.lowerCall(MIRBuilder, TLI.getLibcallCallingConv(Libcall),
                      MachineOperand::CreateES(Name), Result, Args))
     return LegalizerHelper::UnableToLegalize;
-
-  // We're about to remove MI, so move the insert point after it.
-  MIRBuilder.setInsertPt(MIRBuilder.getMBB(),
-                         std::next(MIRBuilder.getInsertPt()));
-
-  MI.eraseFromParent();
   return LegalizerHelper::Legalized;
 }
 
@@ -123,10 +117,9 @@ static LegalizerHelper::LegalizeResult
 simpleLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, unsigned Size,
               Type *OpType) {
   auto Libcall = getRTLibDesc(MI.getOpcode(), Size);
-  return replaceWithLibcall(MI, MIRBuilder, Libcall,
-                            {MI.getOperand(0).getReg(), OpType},
-                            {{MI.getOperand(1).getReg(), OpType},
-                             {MI.getOperand(2).getReg(), OpType}});
+  return createLibcall(MIRBuilder, Libcall, {MI.getOperand(0).getReg(), OpType},
+                       {{MI.getOperand(1).getReg(), OpType},
+                        {MI.getOperand(2).getReg(), OpType}});
 }
 
 LegalizerHelper::LegalizeResult
@@ -135,6 +128,8 @@ LegalizerHelper::libcall(MachineInstr &MI) {
   unsigned Size = LLTy.getSizeInBits();
   auto &Ctx = MIRBuilder.getMF().getFunction()->getContext();
 
+  MIRBuilder.setInstr(MI);
+
   switch (MI.getOpcode()) {
   default:
     return UnableToLegalize;
@@ -143,15 +138,24 @@ LegalizerHelper::libcall(MachineInstr &MI) {
   case TargetOpcode::G_SREM:
   case TargetOpcode::G_UREM: {
     Type *HLTy = Type::getInt32Ty(Ctx);
-    return simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    if (Status != Legalized)
+      return Status;
+    break;
   }
   case TargetOpcode::G_FADD:
   case TargetOpcode::G_FPOW:
   case TargetOpcode::G_FREM: {
     Type *HLTy = Size == 64 ? Type::getDoubleTy(Ctx) : Type::getFloatTy(Ctx);
-    return simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    if (Status != Legalized)
+      return Status;
+    break;
   }
   }
+
+  MI.eraseFromParent();
+  return Legalized;
 }
 
 LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,