99 lines
2.5 KiB
NASM
99 lines
2.5 KiB
NASM
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;
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;;; Microsoft Research Singularity
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;;;
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;;; Copyright (c) Microsoft Corporation. All rights reserved.
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;;;
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;;; This file contains ARM-specific assembly code.
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;;;
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;
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; void *
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; memset( void *dest, int c, size_t count );
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;
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; The memset function sets the first count bytes of
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; dest to the character c (value).
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;
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OPT 2 ; disable listing
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INCLUDE kxarm.inc
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OPT 1 ; reenable listing
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value RN R1 ; int c
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count RN R2
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dest RN R3
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temp RN R12
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IF Thumbing
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THUMBAREA
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ENDIF
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NESTED_ENTRY memset
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PROLOG_END
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IF Thumbing
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; Switch from Thumb mode to ARM mode
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DCW 0x4778 ; bx pc
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DCW 0x46C0 ; nop
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ENDIF
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SUBS count, count, #4
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MOV dest, R0 ;Save R0 for return
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BLT BYTESET
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AND value, value, #&FF
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ORR value, value, value, LSL #8
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CHECKALIGN ; 2-3 cycles
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ANDS temp, dest, #3 ;Check alignment and fix if possible
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BNE ALIGN
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BLOCKSET ; 6-7 cycles
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ORR value, value, value, LSL #16
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SUBS count, count, #12
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MOV temp, value
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BLT BLKSET8
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BLKSET16 ; 7 cycles/16 bytes
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STMIA dest!, {value, temp}
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SUBS count, count, #16
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STMIA dest!, {value, temp}
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BGE BLKSET16
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BLKSET8 ; 4 cycles/8 bytes
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ADDS count, count, #8
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STMGEIA dest!, {value, temp}
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SUBGE count, count, #8
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BLKSET4
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ADDS count, count, #4 ; 4 cycles/4 bytes
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STRGE value, [dest], #4
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BYTESET
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ADDLTS count, count, #4
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BEQ EXIT
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STRB value, [dest], #1 ; 5 cycles/1-3bytes
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CMP count, #2
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STRGEB value, [dest], #1
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STRGTB value, [dest], #1
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EXIT
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IF Interworking :LOR: Thumbing
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BX lr
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ELSE
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MOV pc, lr
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ENDIF
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ALIGN ; 8 cycles/1-3 bytes
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TST dest, #1 ;Check byte alignment
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SUBNE count, count, #1
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STRNEB value, [dest], #1
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TST dest, #2 ;Check Half-word alignment
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SUBNE count, count, #2
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STRNEH value, [dest], #2
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B BLOCKSET
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ENTRY_END
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END
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