[PATCH] D140837: [AAPointerInfo] fix assertion at the pass-through use of a pointer

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

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HandlePassthroughUser may sometimes create a new entry for the OffsetInfo of a
user in the OffsetInfoMap. This can invalidate outstanding references into the
map, including the one which needs to be copied into the new entry. This
produces invalid offset info that can trigger assertions.

Fixed this by not using references at this point. The bug was originally
introduced in commit ID 0dc0a441323d41b4860668f38d290579e0de130c <https://reviews.llvm.org/rG0dc0a441323d41b4860668f38d290579e0de130c>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D140837

Files:
  llvm/lib/Transforms/IPO/AttributorAttributes.cpp


Index: llvm/lib/Transforms/IPO/AttributorAttributes.cpp
===================================================================
--- llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -1434,11 +1434,10 @@
   DenseMap<Value *, OffsetInfo> OffsetInfoMap;
   OffsetInfoMap[&AssociatedValue].insert(0);
 
-  auto HandlePassthroughUser = [&](Value *Usr, const OffsetInfo &PtrOI,
-                                   bool &Follow) {
-    assert(!PtrOI.isUnassigned() &&
+  auto HandlePassthroughUser = [&](Value *Usr, Value *CurPtr, bool &Follow) {
+    assert(!OffsetInfoMap[CurPtr].isUnassigned() &&
            "Cannot pass through if the input Ptr was not visited!");
-    OffsetInfoMap[Usr] = PtrOI;
+    OffsetInfoMap[Usr] = OffsetInfoMap[CurPtr];
     Follow = true;
     return true;
   };
@@ -1460,7 +1459,7 @@
 
     if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Usr)) {
       if (CE->isCast())
-        return HandlePassthroughUser(Usr, OffsetInfoMap[CurPtr], Follow);
+        return HandlePassthroughUser(Usr, CurPtr, Follow);
       if (CE->isCompare())
         return true;
       if (!isa<GEPOperator>(CE)) {
@@ -1490,7 +1489,7 @@
     if (isa<PtrToIntInst>(Usr))
       return false;
     if (isa<CastInst>(Usr) || isa<SelectInst>(Usr) || isa<ReturnInst>(Usr))
-      return HandlePassthroughUser(Usr, OffsetInfoMap[CurPtr], Follow);
+      return HandlePassthroughUser(Usr, CurPtr, Follow);
 
     // For PHIs we need to take care of the recurrence explicitly as the value
     // might change while we iterate through a loop. For now, we give up if
@@ -1558,7 +1557,7 @@
         if (IsFirstPHIUser || BaseOI == UsrOI) {
           LLVM_DEBUG(dbgs() << "[AAPointerInfo] PHI is invariant " << *CurPtr
                             << " in " << *Usr << "\n");
-          return HandlePassthroughUser(Usr, PtrOI, Follow);
+          return HandlePassthroughUser(Usr, CurPtr, Follow);
         }
 
         LLVM_DEBUG(


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