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

[thomasmorley65]

Reviewers: ,

Description:
Inline assembler fallback for _FPU_SETCW() missing in MINGW libraries

Issue 4943
As Issue 4943 on Windows compilation was triggered by
missing _FPU_SETCW() in the MINGW libraries, an alternate call to
initiate the X87 FPU setup as an inline-assembler command is added
- for MINGW 32 Bit compilation only.

Please review this at https://codereview.appspot.com/577450043/

Affected files (+24, -0 lines):
  M lily/main.cc


Index: lily/main.cc
diff --git a/lily/main.cc b/lily/main.cc
index 
4834ff82aa9b6bb649bfe8fbe863877b56c819d1..cfb04d86f8d0b200c3a6e15ae8a36960b31570fa
 100644
--- a/lily/main.cc
+++ b/lily/main.cc
@@ -192,6 +192,30 @@ configure_fpu ()
 static void
 configure_fpu ()
 {
+#if ((defined (__x86__) || defined (__i386__)) \
+  && defined (__MINGW32__) && defined (__code_model_32__) && 
!defined(__SSE2_MATH__))
+  /* If this is a MINGW compilation (for Windows),
+   * but not using SSE2 arithmetic unit nor is a 64 bit compilation (which 
uses SSE2 by default)
+   * _FPU_SETCW() got lost in the MINGW libraries!
+   * Here is an inline assembler call to execute the same task for the X87 
arithmetic unit.
+   *
+   * TODO: output a message what we're going to do here, _only_ if DEBUG level 
is selected,
+   *       but configure_fpu() is called before the commandline options get 
evaluated.
+   *       At the moment the info message will be blanked on the console, but 
if output is
+   *       directed into a file, most editors will show it.
+   */
+  fprintf(stderr, " X87 FPU setup via asm() ... ");
+  asm(
+      "     push %ebp"
+    "\n     mov  $0x027f, %eax"
+    "\n     push %eax"
+    "\n     mov  %esp, %ebp"
+    "\n     fldcw (%ebp)"
+    "\n     pop %eax"
+    "\n     pop %ebp"
+  );
+  fprintf(stderr, "done.\r                                 \r");
+#endif /* (defined(__x86__) || defined(__i386__)) && defined (__MINGW32__) && 
defined (__code_model_32__) && !defined(__SSE2_MATH__) */
 }
 
 #endif /* defined(__x86__) || defined(__i386__) */