mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-18 15:27:48 +01:00
54 lines
1.5 KiB
NASM
54 lines
1.5 KiB
NASM
;------------------------------------------------------------------------------
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; @file
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; Copyright (C) 2020, vit9696. All rights reserved.
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;
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; All rights reserved.
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;
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; This program and the accompanying materials
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; are licensed and made available under the terms and conditions of the BSD License
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; which accompanies this distribution. The full text of the license may be found at
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; http://opensource.org/licenses/bsd-license.php
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;
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; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;------------------------------------------------------------------------------
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BITS 64
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DEFAULT REL
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SECTION .text
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;------------------------------------------------------------------------------
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; UINT64
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; EFIAPI
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; AsmAddRngJitter (
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; IN UINT64 Value
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; );
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;------------------------------------------------------------------------------
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align 8
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global ASM_PFX(AsmAddRngJitter)
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ASM_PFX(AsmAddRngJitter):
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; This assembly code corresponds to Hamming Weight implementation for targets
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; with fast multiplication.
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; REF: https://en.wikipedia.org/wiki/Hamming_weight#Efficient_implementation
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mov rax, rcx
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shr rax, 1
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mov rdx, 5555555555555555h
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and rdx, rax
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sub rcx, rdx
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mov rax, 3333333333333333h
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mov rdx, rcx
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and rdx, rax
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shr rcx, 2
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and rcx, rax
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add rcx, rdx
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mov rax, rcx
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shr rax, 4
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lea rax, [rax+rcx]
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mov rcx, 0F0F0F0F0F0F0F0Fh
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and rcx, rax
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mov rax, 101010101010101h
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imul rax, rcx
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shr rax, 38h
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ret
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