Fix float->uint conversion for inputs less than 0

[dschuff]

Summary

The spec for these functions says that they should return 0 in this case but
this regressed in r234148. That revision essentially delegates the conversion
to the hardware, but that has different behavior on different platforms (e.g.
it is wrong on x86).

Also fix a typo in the name of __fixunsdfti

[dschuff]

ping! any takers?

[dschuff]

Since this is a pretty trivial fix for a pretty clear regression and violation of the compiler-rt/libgcc spec (such as it is), I'm just going to go ahead and land this. Post-commit review is welcome.

compiler-rt/trunk/lib/builtins/fixunsdfdi.c

 #ifndef __SOFT_FP__
 /* Support for systems that have hardware floating-point; can set the invalid
  * flag as a side-effect of computation.
  */
 
 COMPILER_RT_ABI du_int
 __fixunsdfdi(double a)
 {
+    if (a <= 0.0) return 0;
     su_int high = a/0x1p32f;
     su_int low = a - (double)high*0x1p32f;
     return ((du_int)high << 32) | low;
 }
 
 #else
 /* Support for systems that don't have hardware floating-point; there are no
  * flags to set, and we don't want to code-gen to an unknown soft-float

compiler-rt/trunk/lib/builtins/fixunsdfti.c

 
 #ifdef CRT_HAS_128BIT
 #define DOUBLE_PRECISION
 #include "fp_lib.h"
 typedef tu_int fixuint_t;
 #include "fp_fixuint_impl.inc"
 
 COMPILER_RT_ABI tu_int
-__fixunsdftti(fp_t a) {
+__fixunsdfti(fp_t a) {
     return __fixuint(a);
 }
 #endif /* CRT_HAS_128BIT */

compiler-rt/trunk/lib/builtins/fixunssfdi.c

 #ifndef __SOFT_FP__
 /* Support for systems that have hardware floating-point; can set the invalid
  * flag as a side-effect of computation.
  */
 
 COMPILER_RT_ABI du_int
 __fixunssfdi(float a)
 {
+    if (a <= 0.0f) return 0;
     double da = a;
     su_int high = da/0x1p32f;
     su_int low = da - (double)high*0x1p32f;
     return ((du_int)high << 32) | low;
 }
 
 #else
 /* Support for systems that don't have hardware floating-point; there are no