[PowerPC] Fix a DAG replacement bug in PPCTargetLowering::DAGCombineExtBoolTrunc

While promoting nodes in PPCTargetLowering::DAGCombineExtBoolTrunc, it is
possible for one of the nodes to be replaced by another. To make sure we do not
visit the deleted nodes, and to make sure we visit the replacement nodes, use a
list of HandleSDNodes to track the to-be-promoted nodes during the promotion
process.

The same fix has been applied to the analogous code in
PPCTargetLowering::DAGCombineTruncBoolExt.

Fixes PR26985.

llvm-svn: 269272

1 files changed, 19 insertions, 10 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index bb6a0c5bbd3..2607df1e3f8 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -42,6 +42,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetOptions.h"
+#include <list>
 
 using namespace llvm;
 
@@ -9914,14 +9915,18 @@ SDValue PPCTargetLowering::DAGCombineTruncBoolExt(SDNode *N,
       DAG.ReplaceAllUsesOfValueWith(Inputs[i], Inputs[i].getOperand(0));
   }
 
+  std::list<HandleSDNode> PromOpHandles;
+  for (auto &PromOp : PromOps)
+    PromOpHandles.emplace_back(PromOp); 
+
   // Replace all operations (these are all the same, but have a different
   // (i1) return type). DAG.getNode will validate that the types of
   // a binary operator match, so go through the list in reverse so that
   // we've likely promoted both operands first. Any intermediate truncations or
   // extensions disappear.
-  while (!PromOps.empty()) {
-    SDValue PromOp = PromOps.back();
-    PromOps.pop_back();
+  while (!PromOpHandles.empty()) {
+    SDValue PromOp = PromOpHandles.back().getValue();
+    PromOpHandles.pop_back();
 
     if (PromOp.getOpcode() == ISD::TRUNCATE ||
         PromOp.getOpcode() == ISD::SIGN_EXTEND ||
@@ -9930,7 +9935,7 @@ SDValue PPCTargetLowering::DAGCombineTruncBoolExt(SDNode *N,
       if (!isa<ConstantSDNode>(PromOp.getOperand(0)) &&
           PromOp.getOperand(0).getValueType() != MVT::i1) {
         // The operand is not yet ready (see comment below).
-        PromOps.insert(PromOps.begin(), PromOp);
+        PromOpHandles.emplace_front(PromOp);
         continue;
       }
 
@@ -9957,7 +9962,7 @@ SDValue PPCTargetLowering::DAGCombineTruncBoolExt(SDNode *N,
       // promoted (this should be rare because we're going through the
       // list backward, but if one of the operands has several users in
       // this cluster of to-be-promoted nodes, it is possible).
-      PromOps.insert(PromOps.begin(), PromOp);
+      PromOpHandles.emplace_front(PromOp);
       continue;
     }
 
@@ -10164,13 +10169,17 @@ SDValue PPCTargetLowering::DAGCombineExtBoolTrunc(SDNode *N,
         DAG.getAnyExtOrTrunc(InSrc, dl, N->getValueType(0)));
   }
 
+  std::list<HandleSDNode> PromOpHandles;
+  for (auto &PromOp : PromOps)
+    PromOpHandles.emplace_back(PromOp); 
+
   // Replace all operations (these are all the same, but have a different
   // (promoted) return type). DAG.getNode will validate that the types of
   // a binary operator match, so go through the list in reverse so that
   // we've likely promoted both operands first.
-  while (!PromOps.empty()) {
-    SDValue PromOp = PromOps.back();
-    PromOps.pop_back();
+  while (!PromOpHandles.empty()) {
+    SDValue PromOp = PromOpHandles.back().getValue();
+    PromOpHandles.pop_back();
 
     unsigned C;
     switch (PromOp.getOpcode()) {
@@ -10187,7 +10196,7 @@ SDValue PPCTargetLowering::DAGCombineExtBoolTrunc(SDNode *N,
       // promoted (this should be rare because we're going through the
       // list backward, but if one of the operands has several users in
       // this cluster of to-be-promoted nodes, it is possible).
-      PromOps.insert(PromOps.begin(), PromOp);
+      PromOpHandles.emplace_front(PromOp);
       continue;
     }
 
@@ -10199,7 +10208,7 @@ SDValue PPCTargetLowering::DAGCombineExtBoolTrunc(SDNode *N,
            PromOp.getOperand(0).getValueType() != N->getValueType(0)) ||
           (SelectTruncOp[1].count(PromOp.getNode()) &&
            PromOp.getOperand(1).getValueType() != N->getValueType(0))) {
-        PromOps.insert(PromOps.begin(), PromOp);
+        PromOpHandles.emplace_front(PromOp);
         continue;
       }
     }