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.

Current stable/2.20 bcad34e31d7866eb126e73abc89eeeb01faf081f 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: In member function 'double Rational::to_double() const':
rational.cc:48:1: 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
$
```

Current stable/2.20 bcad34e31d7866eb126e73abc89eeeb01faf081f 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
$
```

>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
+    {
+      I64 inum = num_;
+      I64 iden = den_;
+      return static_cast<double> (sign_) *
+        static_cast<double> (inum) / static_cast<double> (iden);
+    }
+#else
     return (double)sign_ * (double)num_ / (double)den_;
+#endif
   if (sign_ == -2)
     return -HUGE_VAL;
   else if (sign_ == 2)
-- 
2.21.0