Mesa (master): glsl: Use conditional-select in mix().
Matt Turner
mattst88 at kemper.freedesktop.org
Mon Sep 9 22:07:59 UTC 2013
Module: Mesa
Branch: master
Commit: fd183fa02c4430e439faf6a5195f5008d34db987
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=fd183fa02c4430e439faf6a5195f5008d34db987
Author: Matt Turner <mattst88 at gmail.com>
Date: Fri Sep 6 12:36:48 2013 -0700
glsl: Use conditional-select in mix().
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
---
src/glsl/builtin_functions.cpp | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp
index 662fc1e..0139b6f 100644
--- a/src/glsl/builtin_functions.cpp
+++ b/src/glsl/builtin_functions.cpp
@@ -2262,14 +2262,14 @@ builtin_builder::_mix_sel(const glsl_type *val_type, const glsl_type *blend_type
ir_variable *a = in_var(blend_type, "a");
MAKE_SIG(val_type, v130, 3, x, y, a);
- if (blend_type->vector_elements == 1) {
- body.emit(assign(x, y, a));
- } else {
- for (int i = 0; i < blend_type->vector_elements; i++) {
- body.emit(assign(x, swizzle(y, i, 1), swizzle(a, i, 1), 1 << i));
- }
- }
- body.emit(ret(x));
+ /* csel matches the ternary operator in that a selector of true choses the
+ * first argument. This differs from mix(x, y, false) which choses the
+ * second argument (to remain consistent with the interpolating version of
+ * mix() which takes a blend factor from 0.0 to 1.0 where 0.0 is only x.
+ *
+ * To handle the behavior mismatch, reverse the x and y arguments.
+ */
+ body.emit(ret(csel(a, y, x)));
return sig;
}
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