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workaround for lame stack packing on i386 ...
- build gcc with -Os (crtfastmath.o to be specific)
- crtfastmath.o is installed into gcc libdir
- run gcc with -ffast-math and get crtfastmath.o linked in
- resulting compiled app segfaults due to init code in
crtfastmath.o that has mis-aligned structure on stack
http://bugs.gentoo.org/147020
http://gcc.gnu.org/PR28621
this is supposed to be fixed in current 4.1 branch, but i'm unable to get
the fix to work so until i can figure out what i'm doing wrong, we'll use
this workaround for now.
--- gcc-4.1.1/gcc/config/i386/crtfastmath.c
+++ gcc-4.1.1/gcc/config/i386/crtfastmath.c
@@ -37,6 +37,23 @@
#define FXSAVE (1 << 24)
#define SSE (1 << 25)
+struct
+{
+ unsigned short int cwd;
+ unsigned short int swd;
+ unsigned short int twd;
+ unsigned short int fop;
+ long int fip;
+ long int fcs;
+ long int foo;
+ long int fos;
+ long int mxcsr;
+ long int mxcsr_mask;
+ long int st_space[32];
+ long int xmm_space[32];
+ long int padding[56];
+} __attribute__ ((aligned (16))) fxsave;
+
static void __attribute__((constructor))
set_fast_math (void)
{
@@ -75,22 +92,6 @@
if (edx & FXSAVE)
{
/* Check if DAZ is available. */
- struct
- {
- unsigned short int cwd;
- unsigned short int swd;
- unsigned short int twd;
- unsigned short int fop;
- long int fip;
- long int fcs;
- long int foo;
- long int fos;
- long int mxcsr;
- long int mxcsr_mask;
- long int st_space[32];
- long int xmm_space[32];
- long int padding[56];
- } __attribute__ ((aligned (16))) fxsave;
__builtin_memset (&fxsave, 0, sizeof (fxsave));
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