r228236 - Driver: Stop forcing frame pointer usage on Windows

[Timur Iskhodzhanov]

ping

Thu Feb 05 2015 at 4:53:30 PM, Timur Iskhodzhanov <timurrrr at google.com>:

> Interesting: this has broken down the dll_noreturn ASan tests (run as part
> of check-asan and check-asan-dynamic), which uses -O0 (yes, o-zero).
> Can you please make sure this doesn't affect -O0?
>
>
> On Thu Feb 05 2015 at 2:52:57 AM Reid Kleckner <reid at kleckner.net> wrote:
>
>> Author: rnk
>> Date: Wed Feb  4 17:45:07 2015
>> New Revision: 228236
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=228236&view=rev
>> Log:
>> Driver: Stop forcing frame pointer usage on Windows
>>
>> Previously, we would use a frame pointer by default on non-Linux OSs. On
>> Linux, any optimization flags imply -fomit-frame-pointer. XCore always
>> defaulted to -fomit-frame-pointer.
>>
>> Now x86 Windows matches our behavior on Linux. All other ISAs supported
>> by Windows (ARM, x64) use xdata information, and frame pointers aren't
>> useful. Frame pointers are now off by default for such targets, but can
>> be forced via -fno-omit-frame-pointer and code using alloca().
>>
>> In fact, on Win64 our frame-pointer prologue is not describable with
>> UNWIND_INFO. This change is a workaround to avoid using the broken FP
>> using prologue for most functions. This is PR22467.
>>
>> Modified:
>>     cfe/trunk/lib/Driver/Tools.cpp
>>
>> Modified: cfe/trunk/lib/Driver/Tools.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Too
>> ls.cpp?rev=228236&r1=228235&r2=228236&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Driver/Tools.cpp (original)
>> +++ cfe/trunk/lib/Driver/Tools.cpp Wed Feb  4 17:45:07 2015
>> @@ -2288,27 +2288,49 @@ static bool addSanitizerRuntimes(const T
>>    return !StaticRuntimes.empty();
>>  }
>>
>> +static bool areOptimizationsEnabled(const ArgList &Args) {
>> +  // Find the last -O arg and see if it is non-zero.
>> +  if (Arg *A = Args.getLastArg(options::OPT_O_Group))
>> +    return !A->getOption().matches(options::OPT_O0);
>> +  // Defaults to -O0.
>> +  return false;
>> +}
>> +
>>  static bool shouldUseFramePointerForTarget(const ArgList &Args,
>>                                             const llvm::Triple &Triple) {
>> -  switch (Triple.getArch()) {
>> -  // Don't use a frame pointer on linux if optimizing for certain
>> targets.
>> -  case llvm::Triple::mips64:
>> -  case llvm::Triple::mips64el:
>> -  case llvm::Triple::mips:
>> -  case llvm::Triple::mipsel:
>> -  case llvm::Triple::systemz:
>> -  case llvm::Triple::x86:
>> -  case llvm::Triple::x86_64:
>> -    if (Triple.isOSLinux())
>> -      if (Arg *A = Args.getLastArg(options::OPT_O_Group))
>> -        if (!A->getOption().matches(options::OPT_O0))
>> -          return false;
>> -    return true;
>> -  case llvm::Triple::xcore:
>> +  // XCore never wants frame pointers, regardless of OS.
>> +  if (Triple.getArch() == llvm::Triple::xcore) {
>>      return false;
>> -  default:
>> -    return true;
>>    }
>> +
>> +  if (Triple.isOSLinux()) {
>> +    switch (Triple.getArch()) {
>> +    // Don't use a frame pointer on linux if optimizing for certain
>> targets.
>> +    case llvm::Triple::mips64:
>> +    case llvm::Triple::mips64el:
>> +    case llvm::Triple::mips:
>> +    case llvm::Triple::mipsel:
>> +    case llvm::Triple::systemz:
>> +    case llvm::Triple::x86:
>> +    case llvm::Triple::x86_64:
>> +      return !areOptimizationsEnabled(Args);
>> +    default:
>> +      return true;
>> +    }
>> +  }
>> +
>> +  if (Triple.isOSWindows()) {
>> +    switch (Triple.getArch()) {
>> +    case llvm::Triple::x86:
>> +      return !areOptimizationsEnabled(Args);
>> +    default:
>> +      // All other supported Windows ISAs use xdata unwind information,
>> so frame
>> +      // pointers are not generally useful.
>> +      return false;
>> +    }
>> +  }
>> +
>> +  return true;
>>  }
>>
>>  static bool shouldUseFramePointer(const ArgList &Args,
>>
>>
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>>
>
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