[PATCH 04/23] sim/erc32: Add FPU support on x86_64 hosts.

Jiri Gaisler
2015-02-17T07:45:35Z

* float.c (get_accex) access FPU control and status words on x64
---
sim/erc32/float.c | 80 +++++++++++++++++++++++--------------------------------
1 file changed, 34 insertions(+), 46 deletions(-)

diff --git a/sim/erc32/float.c b/sim/erc32/float.c
index 598b7cc..ce92a39 100644
--- a/sim/erc32/float.c
+++ b/sim/erc32/float.c
@@ -38,7 +38,6 @@

extern uint32 _get_sw (void);
extern uint32 _get_cw (void);
-static void __setfpucw (unsigned short fpu_control);

/* This host dependent routine should return the accrued exceptions */
int
@@ -46,7 +45,7 @@ get_accex()
{
#ifdef sparc
return ((_get_fsr_raw() >> 5) & 0x1F);
-#elif i386
+#elif defined(i386) || defined(__x86_64__)
uint32 accx;

accx = _get_sw() & 0x3f;
@@ -66,7 +65,7 @@ clear_accex()
{
#ifdef sparc
set_fsr((_get_fsr_raw() & ~0x3e0));
-#elif i386
+#elif defined(i386) || defined(__x86_64__)
asm("\n"
".text\n"
" fnclex\n"
@@ -84,9 +83,8 @@ uint32 fsr;
{
#ifdef sparc
_set_fsr_raw(fsr & ~0x0f800000);
-#elif i386
- void __setfpucw(unsigned short fpu_control);
- uint32 rawfsr;
+#elif defined(i386) || defined(__x86_64__)
+ unsigned short rawfsr;

fsr >>= 30;
switch (fsr) {
@@ -102,9 +100,8 @@ uint32 fsr;
fsr = 1;
break;
}
- rawfsr = _get_cw();
- rawfsr |= (fsr << 10) | 0x3ff;
- __setfpucw(rawfsr);
+ rawfsr = (fsr << 10) | 0x2FF; /* double precision, all traps masked */
+ __asm__ volatile ("fldcw %0" :: "m" (rawfsr));
#else
#warning no fpu trap support for this target
#endif
@@ -175,45 +172,36 @@ uint32 fsr;
"\n"
" ");

+#elif defined(__x86_64__)
+ asm ("\n"
+"\n"
+".text\n"
+".align 8\n"
+".globl _get_sw, __get_sw\n"
+"__get_sw:\n"
+"_get_sw:\n"
+" pushq %rbp\n"
+" movq %rsp, %rbp\n"
+" movl $0, %eax\n"
+" fnstsw %ax\n"
+" movq %rbp, %rsp\n"
+" popq %rbp\n"
+" ret\n"
+".align 8\n"
+".globl _get_cw, __get_cw\n"
+"__get_cw:\n"
+"_get_cw:\n"
+" pushq %rbp\n"
+" movq %rsp, %rbp\n"
+" subq $2, %rsp\n"
+" fnstcw -2(%rbp)\n"
+" movw -2(%rbp), %ax\n"
+" movq %rbp, %rsp\n"
+" popq %rbp\n"
+" ret\n"
+" ");

#else
#warning no fpu trap support for this target
#endif

-#if i386
-/* #if defined _WIN32 || defined __GO32__ */
-/* This is so floating exception handling works on NT
- These definitions are from the linux fpu_control.h, which
- doesn't exist on NT.
-
- default to:
- - extended precision
- - rounding to nearest
- - exceptions on overflow, zero divide and NaN
-*/
-#define _FPU_DEFAULT 0x1372
-#define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
-
-static void
-__setfpucw(unsigned short fpu_control)
-{
- volatile unsigned short cw;
-
- /* If user supplied _fpu_control, use it ! */
- if (!fpu_control)
- {
- /* use defaults */
- fpu_control = _FPU_DEFAULT;
- }
- /* Get Control Word */
- __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-
- /* mask in */
- cw &= _FPU_RESERVED;
- cw = cw | (fpu_control & ~_FPU_RESERVED);
-
- /* set cw */
- __asm__ volatile ("fldcw %0" :: "m" (cw));
-}
-/* #endif */
-#endif
--
2.1.0