[PATCH] D16947: [PGO] assignment operator does not get profile data

[David Blaikie via llvm-commits]

This looks like a change to clang - could you test it in clang (& review it
on cfe-commits instead of llvm-commits)?

On Sat, Feb 6, 2016 at 11:57 AM, David Li via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> davidxl created this revision.
> davidxl added a reviewer: vsk.
> davidxl added subscribers: llvm-commits, cfe-commits.
>
> For compiler generated assignment operator that is not trivial (calling
> base class operator=()), Clang FE assign region counters to the function
> body but does not emit profile counter increment for the function entry.
> This leads to many problems:
>
> 1) the operator body does not have profile data generated leading to
> warning in profile-use
> 2) the size of the function body may be large and lack of profile data may
> lead to wrong inlining decisions
> 3) when FE assign region counters to the function, it also emit coverage
> mapping data for the function -- but it has no coverage data which is
> confusing (currently the llvm-cov tool will report malformed format (as the
> name of the operator is not put into the right name section).
>
> http://reviews.llvm.org/D16947
>
> Files:
>   lib/CodeGen/CGClass.cpp
>   test/Profile/def-assignop.cpp
>
> Index: test/Profile/def-assignop.cpp
> ===================================================================
> --- test/Profile/def-assignop.cpp
> +++ test/Profile/def-assignop.cpp
> @@ -0,0 +1,34 @@
> +// RUN: %clang_cc1 -x c++ %s -triple x86_64-unknown-linux-gnu
> -main-file-name def-assignop.cpp -o - -emit-llvm -fprofile-instrument=clang
> | FileCheck --check-prefix=PGOGEN %s
> +
> +
> +struct B {
> +  int B;
> +  void *operator=(const struct B &b2) {
> +    if (b2.B == 0) {
> +      B = b2.B + 1;
> +    } else
> +      B = b2.B;
> +    return this;
> +  }
> +};
> +
> +struct A : public B {
> +  A &operator=(const A &) = default;
> +// PGOGEN: define {{.*}}@_ZN1AaSERKS_(
> +// PGOGEN: %pgocount = load {{.*}} @__profc__ZN1AaSERKS_
> +// PGOGEN: {{.*}}add{{.*}}%pgocount, 1
> +// PGOGEN: store{{.*}}@__profc__ZN1AaSERKS_
> +  int I;
> +  int J;
> +  int getI() { return I; }
> +};
> +
> +A aa;
> +int g;
> +int main() {
> +  A aa2;
> +  aa2 = aa;
> +
> +  g = aa2.getI();
> +  return 0;
> +}
> Index: lib/CodeGen/CGClass.cpp
> ===================================================================
> --- lib/CodeGen/CGClass.cpp
> +++ lib/CodeGen/CGClass.cpp
> @@ -1608,6 +1608,7 @@
>
>    LexicalScope Scope(*this, RootCS->getSourceRange());
>
> +  incrementProfileCounter(RootCS);
>    AssignmentMemcpyizer AM(*this, AssignOp, Args);
>    for (auto *I : RootCS->body())
>      AM.emitAssignment(I);
>
>
>
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