[GlobalISel] add helper function to create arbitrary libcalls

[gargaroff]

Summary

The existing helper function can only create a libcall to functions available in
RTLIB. Add a helper function that can create a libcall to a given function name
using the provided calling convention.

[gargaroff]

Our downstream target requires this function to lower llvm.trap to a libcall to abort.

[gargaroff]

9fedb6900dd8b9fd54c44d98fe8a2c10880d5a26

llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h

 
 private:
   MachineRegisterInfo &MRI;
   const LegalizerInfo &LI;
   /// To keep track of changes made by the LegalizerHelper.
   GISelChangeObserver &Observer;
 };
 
+/// Helper function that creates a libcall to the given \p Name using the given
+/// calling convention \p CC.
+LegalizerHelper::LegalizeResult
+createLibcall(MachineIRBuilder &MIRBuilder, const char *Name,
+              const CallLowering::ArgInfo &Result,
+              ArrayRef<CallLowering::ArgInfo> Args, CallingConv::ID CC);
+
 /// Helper function that creates the given libcall.
 LegalizerHelper::LegalizeResult
 createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
               const CallLowering::ArgInfo &Result,
               ArrayRef<CallLowering::ArgInfo> Args);
 
 /// Create a libcall to memcpy et al.
 LegalizerHelper::LegalizeResult createMemLibcall(MachineIRBuilder &MIRBuilder,
                                                  MachineRegisterInfo &MRI,
                                                  MachineInstr &MI);
 
 } // End namespace llvm.
 
 #endif

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

static bool isLibCallInTailPosition(MachineInstr &MI) {
   MachineInstr *Next = MI.getNextNode();
   if (!Next || TII.isTailCall(*Next) || !Next->isReturn())
     return false;
 
   return true;
 }
 
 LegalizerHelper::LegalizeResult
-llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
+llvm::createLibcall(MachineIRBuilder &MIRBuilder, const char *Name,
                     const CallLowering::ArgInfo &Result,
-                    ArrayRef<CallLowering::ArgInfo> Args) {
+                    ArrayRef<CallLowering::ArgInfo> Args,
+                    const CallingConv::ID CC) {
   auto &CLI = *MIRBuilder.getMF().getSubtarget().getCallLowering();
-  auto &TLI = *MIRBuilder.getMF().getSubtarget().getTargetLowering();
-  const char *Name = TLI.getLibcallName(Libcall);
 
   CallLowering::CallLoweringInfo Info;
-  Info.CallConv = TLI.getLibcallCallingConv(Libcall);
+  Info.CallConv = CC;
   Info.Callee = MachineOperand::CreateES(Name);
   Info.OrigRet = Result;
   std::copy(Args.begin(), Args.end(), std::back_inserter(Info.OrigArgs));
   if (!CLI.lowerCall(MIRBuilder, Info))
     return LegalizerHelper::UnableToLegalize;
 
   return LegalizerHelper::Legalized;
 }
 
+LegalizerHelper::LegalizeResult
+llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
+                    const CallLowering::ArgInfo &Result,
+                    ArrayRef<CallLowering::ArgInfo> Args) {
+  auto &TLI = *MIRBuilder.getMF().getSubtarget().getTargetLowering();
+  const char *Name = TLI.getLibcallName(Libcall);
+  const CallingConv::ID CC = TLI.getLibcallCallingConv(Libcall);
+  return createLibcall(MIRBuilder, Name, Result, Args, CC);
+}
+
 // Useful for libcalls where all operands have the same type.
 static LegalizerHelper::LegalizeResult
 simpleLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, unsigned Size,
               Type *OpType) {
   auto Libcall = getRTLibDesc(MI.getOpcode(), Size);
 
   SmallVector<CallLowering::ArgInfo, 3> Args;
   for (unsigned i = 1; i < MI.getNumOperands(); i++)

llvm/unittests/CodeGen/GlobalISel/LegalizerHelperTest.cpp

TEST_F(AArch64GISelMITest, BitcastBitOps) {
   CHECK: [[XOR:%[0-9]+]]:_(s32) = G_XOR [[CAST4]]:_, [[CAST5]]:_
   CHECK: [[CAST_XOR:%[0-9]+]]:_(<4 x s8>) = G_BITCAST [[XOR]]
   )";
 
   // Check
   EXPECT_TRUE(CheckMachineFunction(*MF, CheckStr)) << *MF;
 }
 
+TEST_F(AArch64GISelMITest, CreateLibcall) {
+  setUp();
+  if (!TM)
+    return;
+
+  DefineLegalizerInfo(A, {});
+
+  AInfo Info(MF->getSubtarget());
+  DummyGISelObserver Observer;
+
+  LLVMContext &Ctx = MF->getFunction().getContext();
+  auto *RetTy = Type::getVoidTy(Ctx);
+
+  EXPECT_EQ(LegalizerHelper::LegalizeResult::Legalized,
+            createLibcall(B, "abort", {{}, RetTy}, {}, CallingConv::C));
+
+  auto CheckStr = R"(
+  CHECK: ADJCALLSTACKDOWN 0, 0, implicit-def $sp, implicit $sp
+  CHECK: BL &abort
+  CHECK: ADJCALLSTACKUP 0, 0, implicit-def $sp, implicit $sp
+  )";
+
+  // Check
+  EXPECT_TRUE(CheckMachineFunction(*MF, CheckStr)) << *MF;
+}
+
 } // namespace