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

[trueroad]

How about this patch?
Sorry, not tested.

If I understand correctly,
this patch solves not only Issue 4943 but also Issue 4975.
These issues do not only occur on Windows, but on all x86 platforms
except Linux.
`defined (__MINGW32__)` is not necessary.

For Linux-x86, it uses the original precision setting. i.e. _FPU_SETCW
().
For other x86 platforms, it uses Arnold's inline asm for setting
precision.

```
diff --git a/lily/main.cc b/lily/main.cc
index 9145345fff..cba6856159 100644
--- a/lily/main.cc
+++ b/lily/main.cc
@@ -209,19 +209,40 @@ char const *LILYPOND_DATADIR = PACKAGE_DATADIR "/"
TOPLEVEL_VERSION;
    unpredictable places. To get around this, we tell the x87 FPU to use
only
    double precision. Note that this is not needed for x86_64 because
that uses
    the SSE unit by default instead of the x87 FPU. */
-#if ((defined (__x86__) || defined (__i386__)) \
-  && defined (HAVE_FPU_CONTROL_H) && (HAVE_FPU_CONTROL_H == 1))
+#if defined (__x86__) || defined (__i386__)
+// This environment is x86.
+// It is necessary that setting precision by setting x87 FPU control
word.
 
+#if defined (HAVE_FPU_CONTROL_H) && (HAVE_FPU_CONTROL_H == 1)
 #include <fpu_control.h>
+#endif
+
 static void
 configure_fpu ()
 {
+#if defined (HAVE_FPU_CONTROL_H) && (HAVE_FPU_CONTROL_H == 1)
+  // This environment has fpu_control.h. (e.g. Linux glibc)
+  // We use _FPU_SETCW () to set x87 FPU control word.
   fpu_control_t fpu_control = 0x027f;
   _FPU_SETCW (fpu_control);
+#else
+  // This environment doesn't have fpu_control.h. (e.g. MinGW)
+  // We use inline asm to set x87 FPU control word.
+  asm(
+      "     push %ebp"
+    "\n     mov  $0x027f, %eax"
+    "\n     push %eax"
+    "\n     mov  %esp, %ebp"
+    "\n     fldcw (%ebp)"
+    "\n     pop %eax"
+    "\n     pop %ebp"
+  );
+#endif
 }
 
 #else
-
+// This environment isn't x86. (e.g. x86_64)
+// It is unnecessary that setting precision.
 static void
 configure_fpu ()
 {
-- 
```



https://codereview.appspot.com/577450043/