| // Copyright 2021 The Fuchsia Authors |
| // |
| // Use of this source code is governed by a MIT-style |
| // license that can be found in the LICENSE file or at |
| // https://opensource.org/licenses/MIT |
| |
| #include <lib/arch/asm.h> |
| |
| .text |
| |
| // memset implementation that sets 8 bytes at a time when possible |
| // %rax = memset_stosq(%rdi, %rsi, %rdx) |
| .function memset_stosq, global |
| // Save return value. |
| mov %rdi, %r11 |
| |
| // Create an 8-byte copy of the pattern |
| mov %rdx, %rcx |
| movzx %sil, %rax |
| movq $0x0101010101010101, %r10 |
| mul %r10 |
| mov %rcx, %rdx |
| |
| // Copy all of the 8 byte chunks we can |
| shr $3, %rcx |
| rep stosq // while (rcx-- > 0) { *rdi++ = rax; /* rdi is uint64_t* */ } |
| |
| // Copy the rest |
| mov %rdx, %rcx |
| and $0x7, %rcx |
| rep stosb |
| |
| mov %r11, %rax |
| ret |
| .end_function |
