projects / mirror_edk2.git / blame
| Commit | Line | Data |
|---|---|---|
| 102b4c7c HW |
1 | ;------------------------------------------------------------------------------\r |
| 2 | ;\r | |
| 3 | ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>\r | |
| 9344f092 | 4 | ; SPDX-License-Identifier: BSD-2-Clause-Patent\r |
| 102b4c7c HW |
5 | ;\r |
| 6 | ; Module Name:\r | |
| 7 | ;\r | |
| 8 | ; IsZeroBuffer.nasm\r | |
| 9 | ;\r | |
| 10 | ; Abstract:\r | |
| 11 | ;\r | |
| 12 | ; IsZeroBuffer function\r | |
| 13 | ;\r | |
| 14 | ; Notes:\r | |
| 15 | ;\r | |
| 16 | ;------------------------------------------------------------------------------\r | |
| 17 | \r | |
| 18 | DEFAULT REL\r | |
| 19 | SECTION .text\r | |
| 20 | \r | |
| 21 | ;------------------------------------------------------------------------------\r | |
| 22 | ; BOOLEAN\r | |
| 23 | ; EFIAPI\r | |
| 24 | ; InternalMemIsZeroBuffer (\r | |
| 25 | ; IN CONST VOID *Buffer,\r | |
| 26 | ; IN UINTN Length\r | |
| 27 | ; );\r | |
| 28 | ;------------------------------------------------------------------------------\r | |
| 29 | global ASM_PFX(InternalMemIsZeroBuffer)\r | |
| 30 | ASM_PFX(InternalMemIsZeroBuffer):\r | |
| 31 | push rdi\r | |
| 32 | mov rdi, rcx ; rdi <- Buffer\r | |
| 33 | xor rcx, rcx ; rcx <- 0\r | |
| 34 | sub rcx, rdi\r | |
| 35 | and rcx, 15 ; rcx + rdi aligns on 16-byte boundary\r | |
| 36 | jz @Is16BytesZero\r | |
| 37 | cmp rcx, rdx ; Length already in rdx\r | |
| 38 | cmova rcx, rdx ; bytes before the 16-byte boundary\r | |
| 39 | sub rdx, rcx\r | |
| 40 | xor rax, rax ; rax <- 0, also set ZF\r | |
| 41 | repe scasb\r | |
| 42 | jnz @ReturnFalse ; ZF=0 means non-zero element found\r | |
| 43 | @Is16BytesZero:\r | |
| 44 | mov rcx, rdx\r | |
| 45 | and rdx, 15\r | |
| 46 | shr rcx, 4\r | |
| 47 | jz @IsBytesZero\r | |
| 48 | .0:\r | |
| 49 | pxor xmm0, xmm0 ; xmm0 <- 0\r | |
| 50 | pcmpeqb xmm0, [rdi] ; check zero for 16 bytes\r | |
| 51 | pmovmskb eax, xmm0 ; eax <- compare results\r | |
| 52 | ; nasm doesn't support 64-bit destination\r | |
| 53 | ; for pmovmskb\r | |
| 54 | cmp eax, 0xffff\r | |
| 55 | jnz @ReturnFalse\r | |
| 56 | add rdi, 16\r | |
| 57 | loop .0\r | |
| 58 | @IsBytesZero:\r | |
| 59 | mov rcx, rdx\r | |
| 60 | xor rax, rax ; rax <- 0, also set ZF\r | |
| 61 | repe scasb\r | |
| 62 | jnz @ReturnFalse ; ZF=0 means non-zero element found\r | |
| 63 | pop rdi\r | |
| 64 | mov rax, 1 ; return TRUE\r | |
| 65 | ret\r | |
| 66 | @ReturnFalse:\r | |
| 67 | pop rdi\r | |
| 68 | xor rax, rax\r | |
| 69 | ret ; return FALSE\r | |
| 70 | \r |