u_format: fix inv_swizzles generation

inv_swizzles is used in lp_tile_soa.py to create lp_tile_soa.c, we overwrite swizzles if they are already set.

This results in the i8 format getting alpha instead of red, and the l8 format
getting blue instead of red.

Fixes fbo-alphatest-formats, fbo-alphatest-formats ARB_texture_float,
and fbo-alphatest-formats EXT_texture_snorm on llvmpipe.

Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/src/gallium/auxiliary/util/u_format_parse.py b/src/gallium/auxiliary/util/u_format_parse.py
index 73a4bcb..3a39e5b 100755 (executable)
--- a/src/gallium/auxiliary/util/u_format_parse.py
+++ b/src/gallium/auxiliary/util/u_format_parse.py
@@ -196,10 +196,11 @@ class Format:
 
     def inv_swizzles(self):
         '''Return an array[4] of inverse swizzle terms'''
+        '''Only pick the first matching value to avoid l8 getting blue and i8 getting alpha'''
         inv_swizzle = [None]*4
         for i in range(4):
             swizzle = self.swizzles[i]
-            if swizzle < 4:
+            if swizzle < 4 and inv_swizzle[swizzle] == None:
                 inv_swizzle[swizzle] = i
         return inv_swizzle