ref: b3a8a63686f2447dea9c135ab863cee5364b3a07
dir: /libstd/util.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 * %rsp when returning. */ .globl std$cstring .globl _std$cstring _std$cstring: std$cstring: movq (%rsp),%r15 /* ret addr */ movq 8(%rsp),%rsi /* src */ movq 16(%rsp),%rcx /* len */ subq %rcx,%rsp /* get stack */ movq %rsp,%rdi /* dest */ movq %rsp,%rax /* ret val */ subq $16,%rsp /* "unpop" the args */ subq $1,%rsp /* nul */ andq $(~15),%rsp /* align */ cld rep movsb movb $0,(%rdi) /* terminate */ pushq %r15 /* ret addr */ ret .globl std$alloca .globl _std$alloca _std$alloca: std$alloca: movq (%rsp),%r15 /* ret addr */ movq 8(%rsp),%rbx /* len */ /* get stack space */ subq %rbx,%rsp /* get stack space */ movq %rsp,%rax /* top of stack (return value) */ subq $16,%rsp /* "unpop" the args for return */ andq $(~15),%rsp /* align */ pushq %r15 /* ret addr */ ret