[PATCH] D22666: Frontend: Fix mcount inlining bug

[Honggyu Kim via cfe-commits]

honggyu.kim added a comment.

Hi Renato and Saleem,

I found one more testcase that has to be changed. It's in `llvm/tools/clang/test/Frontend/gnu-mcount.c`.
But strangely, some cases provide mcount name with prefix '\01' such as below:

  class ARMTargetInfo : public TargetInfo {
    ...
  public:
    ARMTargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts,
                  bool IsBigEndian)
        : TargetInfo(Triple), FPMath(FP_Default), IsAAPCS(true), LDREX(0),
          HW_FP(0) {
      ...
      if (Triple.getOS() == llvm::Triple::Linux ||
          Triple.getOS() == llvm::Triple::UnknownOS)
        this->MCountName =
            Opts.EABIVersion == "gnu" ? "\01__gnu_mcount_nc" : "\01mcount";
    ...
    }
    ...
  };
  
  class AArch64TargetInfo : public TargetInfo {
    ...
    AArch64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
        : TargetInfo(Triple), ABI("aapcs") {
      ...
      if (Triple.getOS() == llvm::Triple::Linux ||
          Triple.getOS() == llvm::Triple::UnknownOS)
        this->MCountName = Opts.EABIVersion == "gnu" ? "\01_mcount" : "mcount";
      ...
    }
    ...
  };

The modified testcase does not pass because of '\01' prefix.  The following example is reduced version of the testcase.

  $ cat test-mcount.c
  // RUN: %clang -target armv7-unknown-none-eabi -pg -meabi gnu -S -emit-llvm -o - %s | FileCheck %s -check-prefix CHECK -check-prefix CHECK-ARM-EABI-MEABI-GNU
  
  int f() {
    return 0;
  }
  
  // CHECK-LABEL: f
  // CHECK-ARM-EABI-MEABI-GNU: attributes #{{[0-9]+}} = { {{.*}}"counting-function"="\01__gnu_mcount_nc"{{.*}} }

This is not passed only because of '\01' prefix.  It seems that '\01' prefix is analyzed in a strange way when string match is performed by `llvm-lit`.
If I remove \01 prefix in MCountName in `llvm/tools/clang/test/Frontend/gnu-mcount.c` file and recompile it, then test it again, the testcase passes.
Can you please check why '\01' prefix is needed?

Related links:
https://llvm.org/bugs/show_bug.cgi?id=23969
https://llvm.org/bugs/show_bug.cgi?id=27311


https://reviews.llvm.org/D22666