[cfe-commits] [PATCH] Supporting thiscall compatibility with MSVC

Eli Friedman eli.friedman at gmail.com
Thu Feb 16 19:50:45 PST 2012

On Thu, Feb 16, 2012 at 7:38 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
> On Thu, Feb 16, 2012 at 8:52 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>> On Thu, Feb 16, 2012 at 6:25 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>> Here's the next attempt at the MSVC thiscall support patch, this time
>>> with test cases and an improved tablegen declaration.
>>> This is the first time I've done a test case for clang or llvm
>>> codegen, so please pay special attention to the test cases and let me
>>> know if I'm off-base (and what I should do differently).
>> You might want to make the LLVM testcase a bit stronger by using CHECK-NEXT.
> Does CHECK-NEXT basically chain the checks together to check several
> lines as a group?

Basically, yes.

>> +  if (callingConvention == llvm::CallingConv::X86_ThisCall &&
>> +      Context.getLangOptions().MicrosoftMode && RT->isStructureType()) {
>> +    return false;
>> +  }
>> You shouldn't make the behavior of thiscall depend on MicrosoftMode;
>> checking that the calling convention is thiscall should be sufficient.
>>  (If someone explicitly requests thiscall outside of MicrosoftMode,
>> they expect a Microsoft-compatible calling convention.)
> I didn't want to break compatibility if people were already using
> thiscall (for instance, for MinGW compiles).
> Takumi, I believe you know far more about MinGW than I do -- do you
> think this change would break anything if I were to make it the
> default for thiscall instead of MicrosoftMode only?

Note that MicrosoftMode isn't the right way to check for mingw anyway;
take a look at how IsWin32FloatStructABI works.


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