The x86 sampler JIT returned zero for a whole sample when a texture level
pointer was null, and for a mipmapped texture it checked the next level
too, even when it isn't blended in. Tactics Ogre draws its font from a
mipmapped texture whose next level has an invalid address, at level 0,
so all its text was missing on x86-64. The generic samplers read a null
level's texels as zero only where they use that level, and still apply
the texture function. Now samplers for such textures aren't compiled,
and the JIT's null checks are gone. Test: gpu/textures/mipinvalid.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
* samplerjit: Remove unused x/y parameters.
Still need to tune the accuracy of filtering, but those were not the
right way.
* softgpu: Better approximate slope mip level mode.
This isn't exactly right, but it's closer.
* softgpu: Calculate auto from largest difference.
Direction shouldn't matter.
