vc4: Fix sin(0.0) and cos(0.0) accuracy to fix SDL rendering rotation.
SDL has some shaders that compute sin(angle) and cos(angle) for a rotation
matrix in the VS, and angle is usually 0.0. Our previous implementation
had quite a bit of error around 0.0, causing single-pixel rotations at
typical window sizes. SDL2 has changed as of August 28th (commit
12156:
e5a666405750) to not need sin/cos in the VS, but we should still fix
this for existing implementations or similar patterns that other programs
may have.
glsl-cos goes from 32 instructions to 36, but 9 uniforms to 7.
glsl-sin goes from 32 instructions to 34, but 8 uniforms to 7.
This seems like a fine impact to have for the bugfix.
Cc: 18.1 18.2 <mesa-stable@lists.freedesktop.org>
Fixes: https://github.com/anholt/mesa/issues/110