GlobalISel: select G_[SU]MULH on AArch64.

Hopefully this'll be nuked by tablegen pretty soon, but until then it's
reasonably important for supporting C++ operator new[].

llvm-svn: 294520

lib/Target/AArch64/AArch64InstructionSelector.cpp

@@ -715,6 +715,34 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
     return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
   }
 
+  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 unsigned DefReg = I.getOperand(0).getReg();
+    const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
+
+    if (RB.getID() != AArch64::GPRRegBankID) {
+      DEBUG(dbgs() << "G_[SU]MULH on bank: " << RB << ", expected: GPR\n");
+      return false;
+    }
+
+    if (Ty != LLT::scalar(64)) {
+      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_MUL: {
     // Reject the various things we don't support yet.
     if (unsupportedBinOp(I, RBI, MRI, TRI))

test/CodeGen/AArch64/GlobalISel/arm64-instructionselect.mir

@@ -36,6 +36,8 @@
   define void @mul_s32_gpr() { ret void }
   define void @mul_s64_gpr() { ret void }
 
+  define void @mulh_s64_gpr() { ret void }
+
   define void @sdiv_s32_gpr() { ret void }
   define void @sdiv_s64_gpr() { ret void }
 
@@ -698,6 +700,34 @@ body:             |
     %2(s64) = G_MUL %0, %1
 ...
 
+---
+# Same as mul_s32_gpr for the s64 type.
+# CHECK-LABEL: name: mulh_s64_gpr
+name:            mulh_s64_gpr
+legalized:       true
+regBankSelected: true
+
+# CHECK:      registers:
+# CHECK-NEXT:  - { id: 0, class: gpr64 }
+# CHECK-NEXT:  - { id: 1, class: gpr64 }
+# CHECK-NEXT:  - { id: 2, class: gpr64 }
+# CHECK-NEXT:  - { id: 3, class: gpr64 }
+
+# CHECK:  body:
+# CHECK:    %0 = COPY %x0
+# CHECK:    %1 = COPY %x1
+# CHECK:    %2 = SMULHrr %0, %1
+# CHECK:    %3 = UMULHrr %0, %1
+body:             |
+  bb.0:
+    liveins: %x0, %x1
+
+    %0:gpr(s64) = COPY %x0
+    %1:gpr(s64) = COPY %x1
+    %2:gpr(s64) = G_SMULH %0, %1
+    %3:gpr(s64) = G_UMULH %0, %1
+...
+
 ---
 # Same as add_s32_gpr, for G_SDIV operations.
 # CHECK-LABEL: name: sdiv_s32_gpr