In the old code, we would generate the exact same instruction for
extract_u8(some_u64, 0) and extract_u8(some_u64, 1). The mask-a-word
trick only works for even numbered bytes.
This fixes the (new) piglit test
tests/spec/arb_gpu_shader_int64/execution/fs-ushr-and-mask.shader_test.
v2: Use a SHR instead of an AND. This saves an instruction compared to
using two moves. Suggested by Jason.
Fixes: 6ac2d16901 ("i965/fs: Fix extract_i8/u8 to a 64-bit destination")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Ian Romanick
55e6454d5e