ARM: don't use a deleted node as the BaseReg in complex pattern.

We mutated the DAG, which invalidated the node we were trying to use
as a base register. Sometimes we got away with it, but other times the
node really did get deleted before it was finished with.

Should fix PR25733

llvm-svn: 255120

2 files changed, 19 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index cd73021dfc6..024244092a3 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -548,8 +548,11 @@ bool ARMDAGToDAGISel::SelectImmShifterOperand(SDValue N,
     unsigned PowerOfTwo = 0;
     SDValue NewMulConst;
     if (canExtractShiftFromMul(N, 31, PowerOfTwo, NewMulConst)) {
+      BaseReg = SDValue(Select(CurDAG->getNode(ISD::MUL, SDLoc(N), MVT::i32,
+                                               N.getOperand(0), NewMulConst)
+                                   .getNode()),
+                        0);
       replaceDAGValue(N.getOperand(1), NewMulConst);
-      BaseReg = N;
       Opc = CurDAG->getTargetConstant(ARM_AM::getSORegOpc(ARM_AM::lsl,
                                                           PowerOfTwo),
                                       SDLoc(N), MVT::i32);
diff --git a/llvm/test/CodeGen/ARM/shifter_operand.ll b/llvm/test/CodeGen/ARM/shifter_operand.ll
index 11a8ee6ef7d..5d44eb0f11d 100644
--- a/llvm/test/CodeGen/ARM/shifter_operand.ll
+++ b/llvm/test/CodeGen/ARM/shifter_operand.ll
@@ -224,3 +224,18 @@ entry:
   %conv = zext i8 %0 to i32
   ret i32 %conv
 }
+
+
+define void @test_well_formed_dag(i32 %in1, i32 %in2, i32* %addr) {
+; CHECK-LABEL: test_well_formed_dag:
+; CHECK-ARM: movw [[SMALL_CONST:r[0-9]+]], #675
+; CHECK-ARM: mul [[SMALL_PROD:r[0-9]+]], r0, [[SMALL_CONST]]
+; CHECK-ARM: add {{r[0-9]+}}, r1, [[SMALL_PROD]], lsl #7
+
+  %mul.small = mul i32 %in1, 675
+  store i32 %mul.small, i32* %addr
+  %mul.big = mul i32 %in1, 86400
+  %add = add i32 %in2, %mul.big
+  store i32 %add, i32* %addr
+  ret void
+}