When legalising shifts, do not pre-build a list of operands which

may be RAUW'd by the recursive call to LegalizeOps; instead, retrieve
the other operands when calling UpdateNodeOperands.  Fixes PR12889.

llvm-svn: 157162

2 files changed, 32 insertions, 10 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 32973cceb28..b8cb897a86f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -817,9 +817,7 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
   }
 
   if (SimpleFinishLegalizing) {
-    SmallVector<SDValue, 8> Ops;
-    for (unsigned i = 0, e = Node->getNumOperands(); i != e; ++i)
-      Ops.push_back(Node->getOperand(i));
+    SDNode *NewNode = Node;
     switch (Node->getOpcode()) {
     default: break;
     case ISD::SHL:
@@ -829,11 +827,14 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
     case ISD::ROTR:
       // Legalizing shifts/rotates requires adjusting the shift amount
       // to the appropriate width.
-      if (!Ops[1].getValueType().isVector()) {
-        SDValue SAO = DAG.getShiftAmountOperand(Ops[0].getValueType(), Ops[1]);
+      if (!Node->getOperand(1).getValueType().isVector()) {
+        SDValue SAO =
+          DAG.getShiftAmountOperand(Node->getOperand(0).getValueType(),
+                                    Node->getOperand(1));
         HandleSDNode Handle(SAO);
         LegalizeOp(SAO.getNode());
-        Ops[1] = Handle.getValue();
+        NewNode = DAG.UpdateNodeOperands(Node, Node->getOperand(0),
+                                         Handle.getValue());
       }
       break;
     case ISD::SRL_PARTS:
@@ -841,16 +842,19 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
     case ISD::SHL_PARTS:
       // Legalizing shifts/rotates requires adjusting the shift amount
       // to the appropriate width.
-      if (!Ops[2].getValueType().isVector()) {
-        SDValue SAO = DAG.getShiftAmountOperand(Ops[0].getValueType(), Ops[2]);
+      if (!Node->getOperand(2).getValueType().isVector()) {
+        SDValue SAO =
+          DAG.getShiftAmountOperand(Node->getOperand(0).getValueType(),
+                                    Node->getOperand(2));
         HandleSDNode Handle(SAO);
         LegalizeOp(SAO.getNode());
-        Ops[2] = Handle.getValue();
+        NewNode = DAG.UpdateNodeOperands(Node, Node->getOperand(0),
+                                         Node->getOperand(1),
+                                         Handle.getValue());
       }
       break;
     }
 
-    SDNode *NewNode = DAG.UpdateNodeOperands(Node, Ops.data(), Ops.size());
     if (NewNode != Node) {
       DAG.ReplaceAllUsesWith(Node, NewNode);
       for (unsigned i = 0, e = Node->getNumValues(); i != e; ++i)
diff --git a/llvm/test/CodeGen/X86/pr12889.ll b/llvm/test/CodeGen/X86/pr12889.ll
new file mode 100644
index 00000000000..331d8f907d5
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr12889.ll
@@ -0,0 +1,18 @@
+; RUN: llc < %s -march=x86
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@c0 = common global i8 0, align 1
+
+define void @func() nounwind uwtable {
+entry:
+  %0 = load i8* @c0, align 1, !tbaa !0
+  %tobool = icmp ne i8 %0, 0
+  %conv = zext i1 %tobool to i8
+  %storemerge = shl nuw nsw i8 %conv, %conv
+  store i8 %storemerge, i8* @c0, align 1
+  ret void
+}
+
+!0 = metadata !{metadata !"omnipotent char", metadata !1}
+!1 = metadata !{metadata !"Simple C/C++ TBAA"}