Fix cross-compiling librt by enabling x86_64 optimisations with pragmas#20815
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ilevkivskyi merged 1 commit intopython:masterfrom Feb 16, 2026
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Fix cross-compiling librt by enabling x86_64 optimisations with pragmas#20815ilevkivskyi merged 1 commit intopython:masterfrom
ilevkivskyi merged 1 commit intopython:masterfrom
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chewi
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Okay, so it isn't normally built with |
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I suggest surrounding the pramas with checks for the appropriate compiler |
Although Python still lacks a supported method to cross-compile packages, many downstreams do it anyway, so librt should allow this. The current approach of enabling x86_64 optimisations after checking platform.machine() is broken. When building on x86_64 for another architecture, the build fails because the optimisations get enabled when they shouldn't. Conversely, when building on another architecture for x86_64, the build fails because the optimisations don't get enabled when they should. GCC supports enabling an optimisation with a pragma from that line onwards. Clang requires the optimisation to be pushed on and popped off the stack. Unfortunately, MSVC does not have an equivalent feature, but it is unlikely anyone would cross-compile to x86_64 with that. The remaining logic for MSVC could be simplified, but it looks like other compilers like Borland are potentially supported? I considered checking for x86_64 using CCompiler's preprocess() instead, but this seemed awkward. This has been tested with GCC and Clang, including with AVX512 enabled.
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Okay, done that. |
mr-c
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Although Python still lacks a supported method to cross-compile packages, many downstreams do it anyway, so librt should allow this.
The current approach of enabling x86_64 optimisations after checking
platform.machine()is broken. When building on x86_64 for another architecture, the build fails because the optimisations get enabled when they shouldn't. Conversely, when building on another architecture for x86_64, the build fails because the optimisations don't get enabled when they should.GCC supports enabling an optimisation with a pragma from that line onwards. Clang requires the optimisation to be pushed on and popped off the stack. Unfortunately, MSVC does not have an equivalent feature, but it is unlikely anyone would cross-compile to x86_64 with that.
The remaining logic for MSVC could be simplified, but it looks like other compilers like Borland are potentially supported?
I considered checking for x86_64 using CCompiler's
preprocess()instead, but this seemed awkward.This has been tested with GCC and Clang, including with AVX512 enabled.
Supersedes mypyc/librt#32.