r267904 - Debug info: Apply an artificial debug location to __cyg_profile_func.* calls.

[Adrian Prantl via cfe-commits]

> On Apr 28, 2016, at 12:53 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> 
> On Thu, Apr 28, 2016 at 12:50 PM, Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:
> 
>> On Apr 28, 2016, at 12:34 PM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote:
>> 
>> Should these have no/artificial location? It seems like perhaps they should have the same location as the scope they're for? (well, the beginning or end of that scope, respectively, etc)
> 
> While there is usually a single source location for the beginning of the function, there can be more than one such location for the end of the function, so I don’t think this is generally possible.
> 
> Seems to me like it would be - declare a variable with a non-trivial dtor at the start of the function. Whichever line the dtor call is attributed to, that's the end of the function. (I think we use the } for this, or perhaps the final return statement if there is one and only one - I forget the specifics)

Ah yes, I guess we could be using the cleanup location of the function for this.

>  
> The artificial location unambiguously marks the function call as something that does not appear in source code. For a (terrible) example (given the nature of these function calls :-p) if you look at a profile you wouldn’t want these function calls to be misattributed to any line in the source code.
> 
> I'm not quite sure what the ramifications of that would be/why that would be bad (or good) - could you explain further?

If the compiler generates code that does not have any meaningful source location (in this case one could argue that ‘{‘ and ‘}’ might be meaningful source locations?) then I wouldn’t want that code to be attributed to a source location just because the instructions immediately follow some completely unrelated instructions that happen to have a source location.
- Profiling: It shouldn't show up in a profile counted towards the source location of the instructions before it.
- Debugging: Since there is no source code for it a source-based debugger (you can still switch to disassembly) should treat the function call as transparent and skip over it as if it didn’t exist.

-- adrian

> 
> - Dave
>  
> 
> -- adrian
> 
>> 
>> On Thu, Apr 28, 2016 at 10:21 AM, Adrian Prantl via cfe-commits <cfe-commits at lists.llvm.org <mailto:cfe-commits at lists.llvm.org>> wrote:
>> Author: adrian
>> Date: Thu Apr 28 12:21:56 2016
>> New Revision: 267904
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=267904&view=rev <http://llvm.org/viewvc/llvm-project?rev=267904&view=rev>
>> Log:
>> Debug info: Apply an artificial debug location to __cyg_profile_func.* calls.
>> The LLVM Verifier expects all inlinable calls in debuggable functions to
>> have a location.
>> 
>> rdar://problem/25818489 <>
>> 
>> Modified:
>>     cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
>>     cfe/trunk/test/CodeGen/instrument-functions.c
>> 
>> Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=267904&r1=267903&r2=267904&view=diff <http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=267904&r1=267903&r2=267904&view=diff>
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Thu Apr 28 12:21:56 2016
>> @@ -401,6 +401,7 @@ bool CodeGenFunction::ShouldInstrumentFu
>>  /// instrumentation function with the current function and the call site, if
>>  /// function instrumentation is enabled.
>>  void CodeGenFunction::EmitFunctionInstrumentation(const char *Fn) {
>> +  auto NL = ApplyDebugLocation::CreateArtificial(*this);
>>    // void __cyg_profile_func_{enter,exit} (void *this_fn, void *call_site);
>>    llvm::PointerType *PointerTy = Int8PtrTy;
>>    llvm::Type *ProfileFuncArgs[] = { PointerTy, PointerTy };
>> 
>> Modified: cfe/trunk/test/CodeGen/instrument-functions.c
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/instrument-functions.c?rev=267904&r1=267903&r2=267904&view=diff <http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/instrument-functions.c?rev=267904&r1=267903&r2=267904&view=diff>
>> ==============================================================================
>> --- cfe/trunk/test/CodeGen/instrument-functions.c (original)
>> +++ cfe/trunk/test/CodeGen/instrument-functions.c Thu Apr 28 12:21:56 2016
>> @@ -1,9 +1,9 @@
>> -// RUN: %clang_cc1 -S -emit-llvm -o - %s -finstrument-functions | FileCheck %s
>> +// RUN: %clang_cc1 -S -debug-info-kind=standalone -emit-llvm -o - %s -finstrument-functions | FileCheck %s
>> 
>>  // CHECK: @test1
>>  int test1(int x) {
>> -// CHECK: __cyg_profile_func_enter
>> -// CHECK: __cyg_profile_func_exit
>> +// CHECK: call void @__cyg_profile_func_enter({{.*}}, !dbg
>> +// CHECK: call void @__cyg_profile_func_exit({{.*}}, !dbg
>>  // CHECK: ret
>>    return x;
>>  }
>> 
>> 
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