[llvm] r215415 - msan: Handle musttail calls

[Reid Kleckner]

Author: rnk
Date: Mon Aug 11 19:12:43 2014
New Revision: 215415

URL: http://llvm.org/viewvc/llvm-project?rev=215415&view=rev
Log:
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

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
    llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll

Modified: llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp?rev=215415&r1=215414&r2=215415&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp Mon Aug 11 19:12:43 2014
@@ -2356,6 +2356,12 @@ struct MemorySanitizerVisitor : public I
       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 I
   }
 
   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;

Modified: llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll?rev=215415&r1=215414&r2=215415&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll (original)
+++ llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll Mon Aug 11 19:12:43 2014
@@ -878,3 +878,16 @@ define void @MismatchedReturnTypeTailCal
 ; 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