[llvm] r206671 - Check whether functions have any lines associated before emitting coverage info for them. This isn't just a size/time saving, gcov may crash on these.

[David Blaikie]

On Fri, Apr 18, 2014 at 4:32 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
> Author: nicholas
> Date: Fri Apr 18 18:32:28 2014
> New Revision: 206671
>
> URL: http://llvm.org/viewvc/llvm-project?rev=206671&view=rev
> Log:
> Check whether functions have any lines associated before emitting coverage info for them. This isn't just a size/time saving, gcov may crash on these.

:( lack of test coverage.

>
> Modified:
>     llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
>
> Modified: llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp?rev=206671&r1=206670&r2=206671&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp (original)
> +++ llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp Fri Apr 18 18:32:28 2014
> @@ -449,6 +449,21 @@ bool GCOVProfiler::runOnModule(Module &M
>    return false;
>  }
>
> +static bool functionHasLines(Function *F) {
> +  // Check whether this function actually has any source lines. Not only
> +  // do these waste space, they also can crash gcov.
> +  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
> +    for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
> +         I != IE; ++I) {
> +      const DebugLoc &Loc = I->getDebugLoc();
> +      if (Loc.isUnknown()) continue;
> +      if (Loc.getLine() != 0)

Well, at least this condition isn't covered - asserting that
Loc.getLine() != 0 just before the condition never asserts in make
check-llvm...

> +        return true;
> +    }
> +  }
> +  return false;
> +}
> +
>  void GCOVProfiler::emitProfileNotes() {
>    NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
>    if (!CU_Nodes) return;
> @@ -474,6 +489,7 @@ void GCOVProfiler::emitProfileNotes() {
>
>        Function *F = SP.getFunction();
>        if (!F) continue;
> +      if (!functionHasLines(F)) continue;
>
>        // gcov expects every function to start with an entry block that has a
>        // single successor, so split the entry block to make sure of that.
> @@ -549,6 +565,7 @@ bool GCOVProfiler::emitProfileArcs() {
>          continue;
>        Function *F = SP.getFunction();
>        if (!F) continue;
> +      if (!functionHasLines(F)) continue;
>        if (!Result) Result = true;
>        unsigned Edges = 0;
>        for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
>
>
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