0652035a57
In theory, compilers should be able to work this out themselves so we can use a simpler version based on the swab() helpers. I have verified that this works on all supported compiler versions (gcc-4.9 and up, clang-10 and up). Looking at the object code produced by gcc-11, I found that the impact is mostly a change in inlining decisions that lead to slightly larger code. In other cases, this version produces explicit byte swaps in place of separate byte access, or comparing against pre-swapped constants. While the source code is clearly simpler, I have not seen an indication of the new version actually producing better code on Arm, so maybe we want to skip this after all. From what I can tell, gcc recognizes the byteswap pattern in the byteshift.h header and can turn it into explicit instructions, but it does not turn a __builtin_bswap32() back into individual bytes when that would result in better output, e.g. when storing a byte-reversed constant. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> |
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| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| vdso | ||
| video | ||
| xen | ||