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1b8a43a0ba
util_cpu_detect is an anti-pattern: it relies on callers high up in the call chain initializing a local implementation detail. As a real example, I added: ...a Mali compiler unit test ...that called bi_imm_f16() to construct an FP16 immediate ...that calls _mesa_float_to_half internally ...that calls util_get_cpu_caps internally, but only on x86_64! ...that relies on util_cpu_detect having been called before. As a consequence, this unit test: ...crashes on x86_64 with USE_X86_64_ASM set ...passes on every other architecture ...works on my local arm64 workstation and on my test board ...failed CI which runs on x86_64 ...needed to have a random util_cpu_detect() call sprinkled in. This is a bad design decision. It pollutes the tree with magic, it causes mysterious CI failures especially for non-x86_64 developers, and it is not justified by a micro-optimization. Instead, let's call util_cpu_detect directly from util_get_cpu_caps, avoiding the footgun where it fails to be called. This cleans up Mesa's design, simplifies the tree, and avoids a class of a (possibly platform-specific) failures. To mitigate the added overhead, wrap it all in a (fast) atomic load check and declare the whole thing as ATTRIBUTE_CONST so the compiler will CSE calls to util_cpu_detect. Co-authored-by: Alyssa Rosenzweig <alyssa@collabora.com> Reviewed-by: Marek Olšák <maraeo@gmail.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15580> |
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