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6deca89e
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2023-03-22T22:33:40
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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>
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