diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -9057,7 +9057,7 @@ unsigned NextOp = N0.getOpcode(); // fold (rot* (rot* x, c2), c1) - // -> (rot* x, ((c1 % bitsize) +- (c2 % bitsize)) % bitsize) + // -> (rot* x, ((c1 % bitsize) +- (c2 % bitsize) + bitsize) % bitsize) if (NextOp == ISD::ROTL || NextOp == ISD::ROTR) { SDNode *C1 = DAG.isConstantIntBuildVectorOrConstantInt(N1); SDNode *C2 = DAG.isConstantIntBuildVectorOrConstantInt(N0.getOperand(1)); @@ -9073,6 +9073,8 @@ if (Norm1 && Norm2) if (SDValue CombinedShift = DAG.FoldConstantArithmetic( CombineOp, dl, ShiftVT, {Norm1, Norm2})) { + CombinedShift = DAG.FoldConstantArithmetic(ISD::ADD, dl, ShiftVT, + {CombinedShift, BitsizeC}); SDValue CombinedShiftNorm = DAG.FoldConstantArithmetic( ISD::UREM, dl, ShiftVT, {CombinedShift, BitsizeC}); return DAG.getNode(N->getOpcode(), dl, VT, N0->getOperand(0), diff --git a/llvm/test/CodeGen/AArch64/rotate.ll b/llvm/test/CodeGen/AArch64/rotate.ll --- a/llvm/test/CodeGen/AArch64/rotate.ll +++ b/llvm/test/CodeGen/AArch64/rotate.ll @@ -18,14 +18,13 @@ ret <2 x i64> %4 } -;; FIXME: This causes miscompile because rot combine +;; This causes miscompile because rot combine ;; doesn't handle negative shift well. define i5 @pr59898(i5 %x) { ; CHECK-LABEL: pr59898: ; CHECK: // %bb.0: -; CHECK-NEXT: lsr w8, w0, #4 -; CHECK-NEXT: bfi w8, w0, #1, #31 -; CHECK-NEXT: mov w0, w8 +; CHECK-NEXT: ubfx w8, w0, #1, #4 +; CHECK-NEXT: orr w0, w8, w0, lsl #4 ; CHECK-NEXT: ret %r1 = call i5 @llvm.fshr.i5(i5 %x, i5 %x, i5 3) %r2 = call i5 @llvm.fshl.i5(i5 %r1, i5 %r1, i5 2)