[Piglit] [PATCH] teximage-colors: fix divide by zero issue

[Brian Paul]

Not exactly sure why, but the max = ~(~0ul << bits) assignment resulted
in max=0 when bits==32 with MinGW.  This caused us to do a divide by zero
and many of the tests failed.

Special-case the 32-bit case and change the arithmetic to be a little
simpler (to me at least).  Change sn_to_float() to be similar.
---
 tests/texturing/teximage-colors.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tests/texturing/teximage-colors.c b/tests/texturing/teximage-colors.c
index 815ef4d..b350b99 100644
--- a/tests/texturing/teximage-colors.c
+++ b/tests/texturing/teximage-colors.c
@@ -189,14 +189,21 @@ valid_combination(GLenum format, GLenum type)
 static float
 un_to_float(unsigned char bits, unsigned int color)
 {
-	unsigned int max = ~(~0ul << bits);
+	unsigned int max;
+	if (bits == 32) {
+		max = 0xffffffffU;
+	}
+	else {
+		assert(bits < 32);
+		max = (1 << bits) - 1;
+	}
 	return (float)color / (float)max;
 }
 
 static float
 sn_to_float(unsigned char bits, int color)
 {
-	int max = ~(~0 << (bits-1));
+	int max = (1 << (bits - 1)) - 1;
 	if (color < -max)
 		color = -max;
 	return (float)color / (float)max;
-- 
1.7.10.4