[Loads] Fix crash in is isDereferenceableAndAlignedPointer()

Summary:
We were trying to add APInt values with different bit sizes after
visiting an addrspacecast instruction which changed the bit width
of the pointer.

Reviewers: majnemer, hfinkel

Subscribers: hfinkel, wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D24774

llvm-svn: 285407

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index af7ccb9dfc9..e46541e6538 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -91,8 +91,11 @@ static bool isDereferenceableAndAlignedPointer(
     // then the GEP (== Base + Offset == k_0 * Align + k_1 * Align) is also
     // aligned to Align bytes.
 
-    return isDereferenceableAndAlignedPointer(Base, Align, Offset + Size, DL,
-                                              CtxI, DT, Visited);
+    // Offset and Size may have different bit widths if we have visited an
+    // addrspacecast, so we can't do arithmetic directly on the APInt values.
+    return isDereferenceableAndAlignedPointer(
+        Base, Align, Offset + Size.sextOrTrunc(Offset.getBitWidth()),
+        DL, CtxI, DT, Visited);
   }
 
   // For gc.relocate, look through relocations