[AArch64][GlobalISel] Select G_MUL.

llvm-svn: 278810

1 files changed, 37 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
index d9469faddd6..ce274c7cf0a 100644
--- a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -246,6 +246,43 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
     return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
   }
 
+  case TargetOpcode::G_MUL: {
+    // Reject the various things we don't support yet.
+    if (unsupportedBinOp(I, RBI, MRI, TRI))
+      return false;
+
+    const unsigned DefReg = I.getOperand(0).getReg();
+    const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
+
+    if (RB.getID() != AArch64::GPRRegBankID) {
+      DEBUG(dbgs() << "G_MUL on bank: " << RB << ", expected: GPR\n");
+      return false;
+    }
+
+    unsigned ZeroReg;
+    unsigned NewOpc;
+    if (Ty == LLT::scalar(32)) {
+      NewOpc = AArch64::MADDWrrr;
+      ZeroReg = AArch64::WZR;
+    } else if (Ty == LLT::scalar(64)) {
+      NewOpc = AArch64::MADDXrrr;
+      ZeroReg = AArch64::XZR;
+    } else {
+      DEBUG(dbgs() << "G_MUL has type: " << Ty << ", expected: "
+                   << LLT::scalar(32) << " or " << LLT::scalar(64) << '\n');
+      return false;
+    }
+
+    I.setDesc(TII.get(NewOpc));
+    I.removeTypes();
+
+    I.addOperand(MachineOperand::CreateReg(ZeroReg, /*isDef=*/false));
+
+    // 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_OR:
   case TargetOpcode::G_XOR:
   case TargetOpcode::G_AND: