[RISCV][GISel] Select trap and debugtrap. (#73171)

Author: topperc

llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp

@@ -71,6 +71,8 @@ class RISCVInstructionSelector : public InstructionSelector {
                     MachineRegisterInfo &MRI) const;
   bool selectFPCompare(MachineInstr &MI, MachineIRBuilder &MIB,
                        MachineRegisterInfo &MRI) const;
+  bool selectIntrinsicWithSideEffects(MachineInstr &MI, MachineIRBuilder &MIB,
+                                      MachineRegisterInfo &MRI) const;
 
   ComplexRendererFns selectShiftMask(MachineOperand &Root) const;
   ComplexRendererFns selectAddrRegImm(MachineOperand &Root) const;
@@ -608,6 +610,8 @@ bool RISCVInstructionSelector::select(MachineInstr &MI) {
     return selectSelect(MI, MIB, MRI);
   case TargetOpcode::G_FCMP:
     return selectFPCompare(MI, MIB, MRI);
+  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
+    return selectIntrinsicWithSideEffects(MI, MIB, MRI);
   default:
     return false;
   }
@@ -1060,6 +1064,29 @@ bool RISCVInstructionSelector::selectFPCompare(MachineInstr &MI,
   return true;
 }
 
+bool RISCVInstructionSelector::selectIntrinsicWithSideEffects(
+    MachineInstr &MI, MachineIRBuilder &MIB, MachineRegisterInfo &MRI) const {
+  assert(MI.getOpcode() == TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS &&
+         "Unexpected opcode");
+  // Find the intrinsic ID.
+  unsigned IntrinID = cast<GIntrinsic>(MI).getIntrinsicID();
+
+  // Select the instruction.
+  switch (IntrinID) {
+  default:
+    return false;
+  case Intrinsic::trap:
+    MIB.buildInstr(RISCV::UNIMP, {}, {});
+    break;
+  case Intrinsic::debugtrap:
+    MIB.buildInstr(RISCV::EBREAK, {}, {});
+    break;
+  }
+
+  MI.eraseFromParent();
+  return true;
+}
+
 namespace llvm {
 InstructionSelector *
 createRISCVInstructionSelector(const RISCVTargetMachine &TM,

llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/trap.mir

@@ -0,0 +1,34 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -run-pass=instruction-select -simplify-mir \
+# RUN:   -verify-machineinstrs %s -o - | FileCheck %s
+# RUN: llc -mtriple=riscv64 -run-pass=instruction-select -simplify-mir \
+# RUN:   -verify-machineinstrs %s -o - | FileCheck %s
+
+---
+name:            test_trap
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    ; CHECK-LABEL: name: test_trap
+    ; CHECK: UNIMP
+    ; CHECK-NEXT: PseudoRET
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.trap)
+    PseudoRET
+
+...
+---
+name:            test_debugtrap
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    ; CHECK-LABEL: name: test_debugtrap
+    ; CHECK: EBREAK
+    ; CHECK-NEXT: PseudoRET
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.debugtrap)
+    PseudoRET
+
+...