[msan] Fix argument shadow alignment.

llvm-svn: 182771

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index d4664a95636..58108290d8d 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -769,14 +769,21 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
           if (AI->hasByValAttr()) {
             // ByVal pointer itself has clean shadow. We copy the actual
             // argument shadow to the underlying memory.
+            // Figure out maximal valid memcpy alignment.
+            unsigned ArgAlign = AI->getParamAlignment();
+            if (ArgAlign == 0) {
+              Type *EltType = A->getType()->getPointerElementType();
+              ArgAlign = MS.TD->getABITypeAlignment(EltType);
+            }
+            unsigned CopyAlign = std::min(ArgAlign, kShadowTLSAlignment);
             Value *Cpy = EntryIRB.CreateMemCpy(
-              getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB),
-              Base, Size, AI->getParamAlignment());
+                getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB), Base, Size,
+                CopyAlign);
             DEBUG(dbgs() << "  ByValCpy: " << *Cpy << "\n");
             (void)Cpy;
             *ShadowPtr = getCleanShadow(V);
           } else {
-            *ShadowPtr = EntryIRB.CreateLoad(Base);
+            *ShadowPtr = EntryIRB.CreateAlignedLoad(Base, kShadowTLSAlignment);
           }
           DEBUG(dbgs() << "  ARG:    "  << *AI << " ==> " <<
                 **ShadowPtr << "\n");
@@ -785,7 +792,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
             setOrigin(A, EntryIRB.CreateLoad(OriginPtr));
           }
         }
-        ArgOffset += DataLayout::RoundUpAlignment(Size, 8);
+        ArgOffset += DataLayout::RoundUpAlignment(Size, kShadowTLSAlignment);
       }
       assert(*ShadowPtr && "Could not find shadow for an argument");
       return *ShadowPtr;