ARM: Fix codegen for rbit intrinsic

[kongyi]

Summary

LLVM generates illegal rbit r0, #352 instruction for llvm.arm.rbit intrinsic. According to ARMARM, rbit only takes register as argument, not immediate. The correct instruction should be rbit <Rd>, <Rm>.

The bug was introduced by r211057.

[t.p.northover]

Hi Yi,

Looks like an obvious change, but could you add/modify a test where the input argument actually *is* a constant integer? (It should still be fine because it's a Constant rather than a TargetConstant in the DAG, but it's as well to have it tested).

You can just commit with that adjustment.

Cheers.

Tim.

[kongyi]

Closed by commit rL216064 (authored by @kongyi).

llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp

 SDValue
 ARMTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG,
                                           const ARMSubtarget *Subtarget) const {
   unsigned IntNo = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
   SDLoc dl(Op);
   switch (IntNo) {
   default: return SDValue();    // Don't custom lower most intrinsics.
   case Intrinsic::arm_rbit: {
-    assert(Op.getOperand(0).getValueType() == MVT::i32 &&
+    assert(Op.getOperand(1).getValueType() == MVT::i32 &&
            "RBIT intrinsic must have i32 type!");
-    return DAG.getNode(ARMISD::RBIT, dl, MVT::i32, Op.getOperand(0));
+    return DAG.getNode(ARMISD::RBIT, dl, MVT::i32, Op.getOperand(1));
   }
   case Intrinsic::arm_thread_pointer: {
     EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
     return DAG.getNode(ARMISD::THREAD_POINTER, dl, PtrVT);
   }
   case Intrinsic::eh_sjlj_lsda: {
     MachineFunction &MF = DAG.getMachineFunction();
     ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();

llvm/trunk/test/CodeGen/AArch64/rbit.ll

+; RUN: llc -mtriple=aarch64-eabi %s -o - | FileCheck %s
+
+; CHECK-LABEL: rbit32
+; CHECK: rbit w0, w0
+define i32 @rbit32(i32 %t) {
+entry:
+  %rbit.i = call i32 @llvm.aarch64.rbit.i32(i32 %t)
+  ret i32 %rbit.i
+}
+
+; CHECK-LABEL: rbit64
+; CHECK: rbit x0, x0
+define i64 @rbit64(i64 %t) {
+entry:
+  %rbit.i = call i64 @llvm.aarch64.rbit.i64(i64 %t)
+  ret i64 %rbit.i
+}
+
+declare i64 @llvm.aarch64.rbit.i64(i64)
+declare i32 @llvm.aarch64.rbit.i32(i32)

llvm/trunk/test/CodeGen/ARM/rbit.ll

+; RUN: llc -mtriple=armv8-eabi %s -o - | FileCheck %s
+
+; CHECK-LABEL: rbit
+; CHECK: rbit r0, r0
+define i32 @rbit(i32 %t) {
+entry:
+  %rbit = call i32 @llvm.arm.rbit(i32 %t)
+  ret i32 %rbit
+}
+
+; CHECK-LABEL: rbit_constant
+; CHECK: mov r0, #0
+; CHECK: rbit r0, r0
+define i32 @rbit_constant() {
+entry:
+  %rbit.i = call i32 @llvm.arm.rbit(i32 0)
+  ret i32 %rbit.i
+}
+
+declare i32 @llvm.arm.rbit(i32)