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authorKenneth Graunke <kenneth@whitecape.org>2017-07-13 16:22:12 -0700
committerKenneth Graunke <kenneth@whitecape.org>2017-07-18 23:48:46 -0700
commit2412c4c81ea0488df865817a0de91ec46e359b72 (patch)
tree36f921a41cd632a1e3535ccbf5ced152a563b52b /src/util
parent0320bb2c6cb27370e2389b392b63f8d05c7cb4c7 (diff)
util: Make CLAMP turn NaN into MIN.
The previous implementation of CLAMP() allowed NaN to pass through unscathed, by failing both comparisons. NaN isn't exactly a value between MIN and MAX, which can break the assumptions of many callers. This patch changes CLAMP to convert NaN to MIN, arbitrarily. Callers that need NaN to be handled in a specific manner should probably open code something, or use a macro specifically designed to do that. Section 2.3.4.1 of the OpenGL 4.5 spec says: "Any representable floating-point value is legal as input to a GL command that requires floating-point data. The result of providing a value that is not a floating-point number to such a command is unspecified, but must not lead to GL interruption or termination. In IEEE arithmetic, for example, providing a negative zero or a denormalized number to a GL command yields predictable results, while providing a NaN or an infinity yields unspecified results." While CLAMP may apply to more than just GL inputs, it seems reasonable to follow those rules, and allow MIN as an "unspecified result". This prevents assertion failures in i965 when running the games "XCOM: Enemy Unknown" and "XCOM: Enemy Within", which call glTexEnv(GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT, -nan(0x7ffff3)); presumably unintentionally. i965 clamps the LOD bias to be in range, and asserts that it's in the proper range when converting to fixed point. NaN is not, so it crashed. We'd like to at least avoid that. Reviewed-by: Roland Scheidegger <sroland@vmware.com> Reviewed-by: Marek Olšák <marek.olsak@amd.com> Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Diffstat (limited to 'src/util')
-rw-r--r--src/util/macros.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/src/util/macros.h b/src/util/macros.h
index a10f1de8145..a66f1bfed07 100644
--- a/src/util/macros.h
+++ b/src/util/macros.h
@@ -244,8 +244,8 @@ do { \
/** Compute ceiling of integer quotient of A divided by B. */
#define DIV_ROUND_UP( A, B ) ( (A) % (B) == 0 ? (A)/(B) : (A)/(B)+1 )
-/** Clamp X to [MIN,MAX] */
-#define CLAMP( X, MIN, MAX ) ( (X)<(MIN) ? (MIN) : ((X)>(MAX) ? (MAX) : (X)) )
+/** Clamp X to [MIN,MAX]. Turn NaN into MIN, arbitrarily. */
+#define CLAMP( X, MIN, MAX ) ( (X)>(MIN) ? ((X)>(MAX) ? (MAX) : (X)) : (MIN) )
/** Minimum of two values: */
#define MIN2( A, B ) ( (A)<(B) ? (A) : (B) )