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lib/libc/arch/amd64/string/bzero.S
43 строки
816 B
guenther
Add ENTRY_NB() macro for doing an ASM function entry without setting
02 янв 2022, 02:47
02 янв 2022, 02:47
ec0f1ad
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/* * Written by J.T. Conklin <jtc@netbsd.org>. * Public domain. * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com> */ #include "DEFS.h" ENTRY_NB(bzero) RETGUARD_SETUP(bzero, r11) movq %rsi,%rdx cld /* set fill direction forward */ xorq %rax,%rax /* set fill data to 0 */ /* * if the string is too short, it's really not worth the overhead * of aligning to word boundaries, etc. So we jump to a plain * unaligned set. */ cmpq $16,%rdx jb L1 movq %rdi,%rcx /* compute misalignment */ negq %rcx andq $7,%rcx subq %rcx,%rdx rep /* zero until word aligned */ stosb movq %rdx,%rcx /* zero by words */ shrq $3,%rcx andq $7,%rdx rep stosq L1: movq %rdx,%rcx /* zero remainder by bytes */ rep stosb RETGUARD_CHECK(bzero, r11) ret END_WEAK(bzero)