kc3-lang/angle

2023-03-22T22:33:40

Add Spirv Instruction to explicitly cast mediump float to 16 bit If the GLSL shader code expects the comparison between two mediump float values returning true, but the SpirV compiler treats one of them as 32-bit, and treats the other one as 16-bit, the comparison would return false instead. The SpirV compiler may not automatically cast the mediump float values to 16 bits, because it may utilize the RelaxedPrecision decoration to keep a mediump float as 32-bit, so that the compiler can avoid the type cast from 32-bit highp to 16-bit mediump. This change adds an additional OpQuantizeToF16 SpirV instruction to explicitly cast mediump float scalar or mediump float vector to 16 bit, if they are assigned with a highp float value. This ensures that if the GLSL shader code ever compares two meiump float values, the SpirV shader compiler is not accidentally comparing a 16 bit with a 32 bit float value. This fixe the deqp test failure on Pixel 6 and Pixel 7: dEQP-GLES2.functional.shaders.algorithm.rgb_to_hsl_vertex. Bug: b/274859104 Bug: b/274408172 Change-Id: Ifd996cea14c0f77f45ae90f38c8e53cf5035139f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4400404 Commit-Queue: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com>