[llvm] [AArch64][GlobalISel] Remove mulh c++ lowering (PR #81105)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: David Green (davemgreen)

<details>
<summary>Changes</summary>

I believe these should be selectable via tablegen patterns nowadays.

---
Full diff: https://github.com/llvm/llvm-project/pull/81105.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp (-28) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
index 2515991fbea11..9d51a7f7616dd 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -3020,34 +3020,6 @@ bool AArch64InstructionSelector::select(MachineInstr &I) {
   case TargetOpcode::G_INDEXED_STORE:
     return selectIndexedStore(cast<GIndexedStore>(I), MRI);
 
-  case TargetOpcode::G_SMULH:
-  case TargetOpcode::G_UMULH: {
-    // Reject the various things we don't support yet.
-    if (unsupportedBinOp(I, RBI, MRI, TRI))
-      return false;
-
-    const Register DefReg = I.getOperand(0).getReg();
-    const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
-
-    if (RB.getID() != AArch64::GPRRegBankID) {
-      LLVM_DEBUG(dbgs() << "G_[SU]MULH on bank: " << RB << ", expected: GPR\n");
-      return false;
-    }
-
-    if (Ty != LLT::scalar(64)) {
-      LLVM_DEBUG(dbgs() << "G_[SU]MULH has type: " << Ty
-                        << ", expected: " << LLT::scalar(64) << '\n');
-      return false;
-    }
-
-    unsigned NewOpc = I.getOpcode() == TargetOpcode::G_SMULH ? AArch64::SMULHrr
-                                                             : AArch64::UMULHrr;
-    I.setDesc(TII.get(NewOpc));
-
-    // Now that we selected an opcode, we need to constrain the register
-    // operands to use appropriate classes.
-    return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
-  }
   case TargetOpcode::G_LSHR:
   case TargetOpcode::G_ASHR:
     if (MRI.getType(I.getOperand(0).getReg()).isVector())

``````````

</details>


https://github.com/llvm/llvm-project/pull/81105