Mesa (gallium-strict-aliasing): mesa: fix strict aliasing issues in half-to-float/float-to-half conversions

Roland Scheidegger sroland at kemper.freedesktop.org
Mon Dec 7 12:49:40 PST 2009


Module: Mesa
Branch: gallium-strict-aliasing
Commit: c36d1aacf4c70d76165c91cd7048c0f9f43b8571
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c36d1aacf4c70d76165c91cd7048c0f9f43b8571

Author: Roland Scheidegger <sroland at vmware.com>
Date:   Mon Dec  7 20:11:46 2009 +0100

mesa: fix strict aliasing issues in half-to-float/float-to-half conversions

use union instead of casts

---

 src/mesa/main/imports.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/mesa/main/imports.c b/src/mesa/main/imports.c
index c9e00cf..f2ef84f 100644
--- a/src/mesa/main/imports.c
+++ b/src/mesa/main/imports.c
@@ -460,7 +460,7 @@ _mesa_inv_sqrtf(float n)
 #if 0 /* not used, see below -BP */
         float r3, x3, y3;
 #endif
-        union { float f; unsigned int i; } u;
+        fi_type u;
         unsigned int magic;
 
         /*
@@ -649,10 +649,10 @@ _mesa_bitcount(unsigned int n)
 GLhalfARB
 _mesa_float_to_half(float val)
 {
-   const int flt = *((int *) (void *) &val);
-   const int flt_m = flt & 0x7fffff;
-   const int flt_e = (flt >> 23) & 0xff;
-   const int flt_s = (flt >> 31) & 0x1;
+   const fi_type fi = {val};
+   const int flt_m = fi.i & 0x7fffff;
+   const int flt_e = (fi.i >> 23) & 0xff;
+   const int flt_s = (fi.i >> 31) & 0x1;
    int s, e, m = 0;
    GLhalfARB result;
    
@@ -739,7 +739,8 @@ _mesa_half_to_float(GLhalfARB val)
    const int m = val & 0x3ff;
    const int e = (val >> 10) & 0x1f;
    const int s = (val >> 15) & 0x1;
-   int flt_m, flt_e, flt_s, flt;
+   int flt_m, flt_e, flt_s;
+   fi_type fi;
    float result;
 
    /* sign bit */
@@ -774,8 +775,8 @@ _mesa_half_to_float(GLhalfARB val)
       flt_m = m << 13;
    }
 
-   flt = (flt_s << 31) | (flt_e << 23) | flt_m;
-   result = *((float *) (void *) &flt);
+   fi.i = (flt_s << 31) | (flt_e << 23) | flt_m;
+   result = fi.f;
    return result;
 }
 



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