glsl: Use a single bit for the dual-source blend index
The only values allowed are 0 and 1, and the value is checked before
assigning.
Valgrind massif results for a trimmed apitrace of dota2:
n time(i) total(B) useful-heap(B) extra-heap(B) stacks(B)
Before (32-bit): 74 40,580,119,657 69,186,544 63,506,327 5,680,217 0
After (32-bit): 76 40,572,916,873 68,831,248 63,328,783 5,502,465 0
Before (64-bit): 89 36,822,971,897 96,526,616 88,735,296 7,791,320 0
After (64-bit): 60 36,822,640,058 96,526,824 88,735,296 7,791,528 0
A real savings of 173KiB on 32-bit and no change on 64-bit.
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 535693d..5032c26 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -689,6 +689,15 @@
unsigned must_be_shader_input:1;
/**
+ * Output index for dual source blending.
+ *
+ * \note
+ * The GLSL spec only allows the values 0 or 1 for the index in \b dual
+ * source blending.
+ */
+ unsigned index:1;
+
+ /**
* \brief Layout qualifier for gl_FragDepth.
*
* This is not equal to \c ir_depth_layout_none if and only if this
@@ -722,11 +731,6 @@
unsigned stream;
/**
- * output index for dual source blending.
- */
- int index;
-
- /**
* Initial binding point for a sampler, atomic, or UBO.
*
* For array types, this represents the binding point for the first element.