Re: Inline assembler fallback for _FPU_SETCW() missing in MINGW libraries (issue 577450043 by address@hidden)

[Masamichi Hosoda]

>>>>> We currently have the problem that the compiler used in GUB for
>>>>> compiling 32bit binaries gets an internal compiler fault for those
>>>>> options.
>>>>> 
>>>>> We'll need to figure out whether a newer compiler does the trick, and if
>>>>> it does, update GUB.  Or find a different way of proceeding.
>>>>> 
>>>>> I'll see whether I can convince my current compilers to generate 32bit
>>>>> code and see whether those are currently up to using those options.  If
>>>>> current compilers don't want them, we'll need to revert to a different
>>>>> plan.
>>>>
>>>> It seems that static cast from `unsigned long long` to `double`
>>>> by x86 SSE2 raises the internal compile error.
>>>> However, static cast from `signed long long` to `double`
>>>> does not raise the errir.
>>>> I think it can be a workaround for rational.cc.
>>>>
>>>> i.e.
>>>> First, static cast from `unsigned long long` to `signed long long`
>>>> Then, static cast from `singed long long` to `double`
>>> 
>>> Oh wow.  I would never have thought one could identify something as
>>> specific.  I think I have convinced my system to build a 32bit Guile,
>>> but have problems convincing LilyPond to do the same.  So I cannot help
>>> with debugging this situation yet or even finding out whether it
>>> persists into newer compiler versions.
>>
>> I've attached the workaround patch for stable/2.20 branch.
>> The results of my experiment is here.
> 
> 
>>>From 2a3816e49067e026c7180dc6a3b2d5614d9c20d6 Mon Sep 17 00:00:00 2001
>> From: Masamichi Hosoda <address@hidden>
>> Date: Tue, 4 Feb 2020 23:30:29 +0900
>> Subject: [PATCH] Add workaround for avoiding GUB darwin-x86 error
>>
>> In GUB, g++ 4.9.4 for darwin-x86 (macOS x86),
>> it seems that static cast from  `unsigned long long` to `double`
>> by x86 SSE2 raises an internal compile error.
>> However, static cast from `signed long long` to `double`
>> does not raise the error.
>> So we use it for a workaround.
>>
>> i.e.
>> First, static cast from `unsigned long long` to `signed long long`.
>> Then, static cast from `singed long long` to `double`.
>> ---
>>  flower/rational.cc | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>>
>> diff --git a/flower/rational.cc b/flower/rational.cc
>> index 559e1646a0..9435edbb8f 100644
>> --- a/flower/rational.cc
>> +++ b/flower/rational.cc
>> @@ -31,7 +31,23 @@ double
>>  Rational::to_double () const
>>  {
>>    if (sign_ == -1 || sign_ == 1 || sign_ == 0)
>> +// FIXME: workaround: In GUB, g++ 4.9.4 for darwin-x86,
>> +// it seems that static cast from `unsigned long long` to `double`
>> +// by x86 SSE2 raises an internal compile error.
>> +// However, static cast from `signed long long` to `double`
>> +// does not raise the error.
>> +// So we use it for a workaround.
>> +#if defined (__i386__) && defined (__APPLE__) && \
>> +  defined (__SSE2_MATH__) && __GNUC__ < 5
> 
> Wouldn't the same problem occur on Windows?  We have 32bit executables
> there as well.  Or is the compiler version we use there not afflicted?

Sorry, I forgot MinGW.
The internal compiler error seems to raise only in darwin-x86.
I don't have newer g++ for darwin-x86, so I'm not sure
if it was fixed in the newer g++.

without the patch:

```
$ ~gub/gub/target/darwin-x86/root/usr/cross/bin/i686-apple-darwin8-g++ -c 
-msse2 -mfpmath=sse -I include -I .. rational.cc
rational.cc:36:5: warning: floating constant exceeds range of 'double' 
[-Woverflow]
     return -HUGE_VAL;
     ^
rational.cc:38:5: warning: floating constant exceeds range of 'double' 
[-Woverflow]
     return HUGE_VAL;
     ^
rational.cc: In member function 'double Rational::to_double() const':
rational.cc:43:1: internal compiler error: in gen_reg_rtx, at emit-rtl.c:838
 }
 ^
0x773934 gen_reg_rtx(machine_mode)
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/emit-rtl.c:838
0xc53c53 gen_split_4130(rtx_def*, rtx_def**)
        
/home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/config/i386/sse.md:884
0x7772a7 try_split(rtx_def*, rtx_def*, int)
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/emit-rtl.c:3444
0x8feb71 split_insn
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/recog.c:2897
0x9034e4 split_all_insns()
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/recog.c:2987
0x903578 rest_of_handle_split_after_reload
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/recog.c:3938
0x903578 execute
        /home/gub/gub/target/darwin-x86/src/cross/gcc-4.9.4/gcc/recog.c:3967
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ ~gub/gub/target/linux-x86/root/usr/cross/bin/i686-linux-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$ ~gub/gub/target/freebsd-x86/root/usr/cross/bin/i686-freebsd6-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$ ~gub/gub/target/mingw/root/usr/cross/bin/i686-mingw32-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$
```

with the patch:

```
$ ~gub/gub/target/darwin-x86/root/usr/cross/bin/i686-apple-darwin8-g++ -c 
-msse2 -mfpmath=sse -I include -I .. rational.cc
rational.cc:52:5: warning: floating constant exceeds range of 'double' 
[-Woverflow]
     return -HUGE_VAL;
     ^
rational.cc:54:5: warning: floating constant exceeds range of 'double' 
[-Woverflow]
     return HUGE_VAL;
     ^
$ ~gub/gub/target/linux-x86/root/usr/cross/bin/i686-linux-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$ ~gub/gub/target/freebsd-x86/root/usr/cross/bin/i686-freebsd6-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$ ~gub/gub/target/mingw/root/usr/cross/bin/i686-mingw32-g++ -c -msse2 
-mfpmath=sse -I include -I .. rational.cc
$
```

g++ version:

```
$ ~gub/gub/target/darwin-x86/root/usr/cross/bin/i686-apple-darwin8-g++ --version
i686-apple-darwin8-g++ (GCC) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ~gub/gub/target/linux-x86/root/usr/cross/bin/i686-linux-g++ --version
i686-linux-g++ (GCC) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ~gub/gub/target/freebsd-x86/root/usr/cross/bin/i686-freebsd6-g++ --version
i686-freebsd6-g++ (GCC) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ~gub/gub/target/mingw/root/usr/cross/bin/i686-mingw32-g++ --version
i686-mingw32-g++ (GCC) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$
```