Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
x86/crc32: improve crc32c_arch() code generation with clang
crc32c_arch() is affected by
https://github.com/llvm/llvm-project/issues/20571 where clang
unnecessarily spills the inputs to "rm"-constrained operands to the
stack. Replace "rm" with ASM_INPUT_RM which partially works around this
by expanding to "r" when the compiler is clang. This results in better
code generation with clang, though still not optimal.
Link: https://lore.kernel.org/r/20250210210741.471725-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
+2
-2
+2
-2
arch/x86/lib/crc32-glue.c
+2
-2
arch/x86/lib/crc32-glue.c
···
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for (num_longs = len / sizeof(unsigned long);
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num_longs != 0; num_longs--, p += sizeof(unsigned long))
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-
asm(CRC32_INST : "+r" (crc) : "rm" (*(unsigned long *)p));
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+
asm(CRC32_INST : "+r" (crc) : ASM_INPUT_RM (*(unsigned long *)p));
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for (len %= sizeof(unsigned long); len; len--, p++)
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-
asm("crc32b %1, %0" : "+r" (crc) : "rm" (*p));
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+
asm("crc32b %1, %0" : "+r" (crc) : ASM_INPUT_RM (*p));
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return crc;
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}