msan: Handle musttail calls

First, avoid calling setTailCall(false) on musttail calls.  The funciton
prototypes should be "congruent", so the shadow layout should be exactly
the same.

Second, avoid inserting instrumentation after a musttail call to
propagate the return value shadow.  We don't need to propagate the
result of a tail call, it should already be in the right place.

Reviewed By: eugenis

Differential Revision: http://reviews.llvm.org/D4331

llvm-svn: 215415

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 3df1d157412..643faacc700 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -2356,6 +2356,12 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       VAHelper->visitCallSite(CS, IRB);
     }
 
+    // If this is a musttail call site, we can't insert propagation code here.
+    // The return type of the caller must match the callee, so the shadow should
+    // already be set up for an immediate return.
+    if (CS.isMustTailCall())
+      return;
+
     // Now, get the shadow for the RetVal.
     if (!I.getType()->isSized()) return;
     IRBuilder<> IRBBefore(&I);
@@ -2389,6 +2395,10 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
   }
 
   void visitReturnInst(ReturnInst &I) {
+    // Don't propagate shadow between musttail calls and the return.
+    if (I.getParent()->getTerminatingMustTailCall())
+      return;
+
     IRBuilder<> IRB(&I);
     Value *RetVal = I.getReturnValue();
     if (!RetVal) return;