mesa: fix possible precision issues in pack/unpack/fetch functions

GLfloat doesn't have enough precision to exactly represent 0xffffff
and 0xffffffff. (and a reciprocal of those, if I am not mistaken)

If -ffast-math is enabled, using GLfloat causes assertion failures in:
- fbo-blit-d24s8
- fbo-depth-sample-compare
- fbo-readpixels-depth-formats
- glean/depthStencil

For example:
fbo-depth-sample-compare: main/format_unpack.c:1769:
unpack_float_z_Z24_X8: Assertion `dst[i] <= 1.0F' failed.

Reviewed-by: Brian Paul <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/swrast/s_texfetch_tmp.h b/src/mesa/swrast/s_texfetch_tmp.h
index e9512b561a9..877c29c9b74 100644
--- a/src/mesa/swrast/s_texfetch_tmp.h
+++ b/src/mesa/swrast/s_texfetch_tmp.h
@@ -2270,7 +2270,7 @@ static void FETCH(f_z24_s8)( const struct swrast_texture_image *texImage,
 {
    /* only return Z, not stencil data */
    const GLuint *src = TEXEL_ADDR(GLuint, texImage, i, j, k, 1);
-   const GLfloat scale = 1.0F / (GLfloat) 0xffffff;
+   const GLdouble scale = 1.0 / (GLdouble) 0xffffff;
    texel[0] = ((*src) >> 8) * scale;
    ASSERT(texImage->Base.TexFormat == MESA_FORMAT_Z24_S8 ||
 	  texImage->Base.TexFormat == MESA_FORMAT_Z24_X8);
@@ -2298,7 +2298,7 @@ static void FETCH(f_s8_z24)( const struct swrast_texture_image *texImage,
 {
    /* only return Z, not stencil data */
    const GLuint *src = TEXEL_ADDR(GLuint, texImage, i, j, k, 1);
-   const GLfloat scale = 1.0F / (GLfloat) 0xffffff;
+   const GLdouble scale = 1.0 / (GLdouble) 0xffffff;
    texel[0] = ((*src) & 0x00ffffff) * scale;
    ASSERT(texImage->Base.TexFormat == MESA_FORMAT_S8_Z24 ||
 	  texImage->Base.TexFormat == MESA_FORMAT_X8_Z24);