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authorDavid Miller <davem@davemloft.net>2009-02-27 23:34:41 -0800
committerBrian Paul <brianp@vmware.com>2009-02-28 09:36:56 -0700
commitae5c06b9ce1191afaa95dd784d7315f25ec729ff (patch)
tree88308e8f91dcbb34e41e3a2d35803069ce086917 /src/mesa/tnl_dd
parent389d50baff8234fdf4d7bcddeb09658d7d17012d (diff)
mesa: Sparc's IROUND() optimization is invalid.
We can't use the "fstoi" instruction like this. Unlike other floating point instructions, "fstoi" always rounds towards zero no matter what rounding mode the FPU has been set to. This was validated using the following test program: -------------------- static inline int iround(float f) { int r; __asm__ ("fstoi %1, %0" : "=f" (r) : "f" (f)); return r; } #define IROUND(x) iround(x) #define IROUND_REF(f) ((int) (((f) >= 0.0F) ? ((f) + 0.5F) : ((f) - 0.5F))) int main(void) { float f = -2.0; while (f < 3.0f) { int sparc_val = IROUND(f); int ref_val = IROUND_REF(f); if (sparc_val != ref_val) printf("DIFFERENT[%f]: REF==%d SPARC==%d\n", f, ref_val, sparc_val); f += 0.1f; } return 0; } -------------------- which prints out things like: -------------------- DIFFERENT[-1.900000]: REF==-2 SPARC==-1 DIFFERENT[-1.800000]: REF==-2 SPARC==-1 DIFFERENT[-1.700000]: REF==-2 SPARC==-1 DIFFERENT[-1.600000]: REF==-2 SPARC==-1 DIFFERENT[-1.000000]: REF==-1 SPARC==0 DIFFERENT[-0.900000]: REF==-1 SPARC==0 DIFFERENT[-0.800000]: REF==-1 SPARC==0 DIFFERENT[-0.700000]: REF==-1 SPARC==0 DIFFERENT[-0.600000]: REF==-1 SPARC==0 DIFFERENT[0.500000]: REF==1 SPARC==0 DIFFERENT[0.600000]: REF==1 SPARC==0 ... -------------------- So we have to remove Sparc's IROUND() definition, it's wrong. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'src/mesa/tnl_dd')
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