Revert r215415 which causse MSan to crash on a great deal of C++ code.

I've followed up on the original commit as well.

llvm-svn: 215532

Author: chandlerc

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -2356,12 +2356,6 @@ 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);
@@ -2395,10 +2389,6 @@ 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;

llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll

@@ -878,16 +878,3 @@ define void @MismatchedReturnTypeTailCall(i32 %a) sanitize_memory {
 ; CHECK-LABEL: define void @MismatchedReturnTypeTailCall
 ; CHECK: tail call i32 @InnerTailCall
 ; CHECK: ret void
-
-declare i32 @InnerMustTailCall(i32 %a)
-
-define i32 @MustTailCall(i32 %a) {
-  %b = musttail call i32 @InnerMustTailCall(i32 %a)
-  ret i32 %b
-}
-
-; Test that 'musttail' is preserved.  The ABI should make this work.
-
-; CHECK-LABEL: define i32 @MustTailCall
-; CHECK: musttail call i32 @InnerMustTailCall
-; CHECK-NEXT: ret i32