[llvm] r215415 - msan: Handle musttail calls

[Reid Kleckner]

Thanks! I'll take a look.


On Wed, Aug 13, 2014 at 2:28 AM, Chandler Carruth <chandlerc at google.com>
wrote:

> Hey Reid,
>
> I've reverted this in r215532 because it causes MSan instrumented compiles
> to crash in the instrumentation pass pretty rampantly on our C++ code. I
> suspect a boot strap would reproduce, but I've also sent you (off list) an
> easy if un-reduced reproduction. I needed to revert it to get the tree
> green while you investigate.
>
> Thanks,
> -Chandler
>
>
> On Mon, Aug 11, 2014 at 5:12 PM, Reid Kleckner <reid at kleckner.net> wrote:
>
>> 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
>>
>>
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>
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