ref: e239a342a21b54d5e2302f5dece5624ef0f1aea7
dir: /libstd/util+plan9.s/
/* * Allocates a C string on the stack, for * use within system calls, which is the only * place the Myrddin stack should need nul-terminated * strings. * * This is in assembly, because for efficiency we * allocate the C strings on the stack, and don't adjust * SP when returning. */ TEXT sys$cstring+0(SB),$0 /* save registers */ PUSHQ BP MOVQ SP,BP PUSHQ R15 PUSHQ SI PUSHQ DI PUSHQ CX MOVQ 8(BP),R15 /* ret addr */ MOVQ 16(BP),SI /* src */ MOVQ 24(BP),CX /* len */ SUBQ CX,SP /* get stack */ SUBQ $1,SP /* +1 for nul */ MOVQ SP,DI /* dest */ MOVQ SP,AX /* ret val */ SUBQ $16,SP /* "unpop" the args */ ANDQ $(~15),SP /* align */ CLD REP; MOVSB MOVB $0,(DI) /* terminate */ PUSHQ R15 /* ret addr */ /* Restore registers */ MOVQ -32(BP),CX MOVQ -24(BP),DI MOVQ -16(BP),SI MOVQ -8(BP),R15 MOVQ (BP),BP RET TEXT sys$alloca+0(SB),$0 /* save registers */ PUSHQ BP MOVQ SP,BP PUSHQ R15 PUSHQ BX MOVQ 8(BP),R15 /* ret addr */ MOVQ 16(BP),BX /* len */ /* get stack space */ SUBQ BX,SP /* get stack space */ MOVQ SP,AX /* top of stack (return value) */ SUBQ $16,SP /* "unpop" the args for return */ ANDQ $(~15),SP /* align */ PUSHQ R15 /* ret addr */ /* restore registers */ MOVQ -16(BP),BX MOVQ -8(BP),R15 MOVQ (BP),BP RET