128 lines
4.8 KiB
NASM
128 lines
4.8 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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; __stou single precision floating point to unsigned integer convert
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;
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; Input: r0 - float to be converted
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; Output: r0 - converted float in unsigned integer format
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;
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; Local stack size and offsets
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LOC_SIZE EQU 0x18
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OrgOp1l EQU 0x14
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ExDResl EQU 0x08
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NewResl EQU 0x10
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GET fpe.asm
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GET kxarm.inc
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AREA |.text|, CODE, READONLY
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Export __stou
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IMPORT FPE_Raise
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NESTED_ENTRY __stou
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EnterWithLR_16
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STMFD sp!, {lr} ; Save return address
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SUB sp, sp, #LOC_SIZE ; Allocate local storage
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PROLOG_END
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MOVS r12, r0 ; Save original arg in case of exception
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MOV r3, #_FpSToU ; Initialize opcode, no exceptions
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MOVS r2, r0, ASR #SFrc_len ; Right justify exponent, save sign bit
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MOV r0, r0, LSL #SExp_len ; Left justify mantissa and
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ORR r0, r0, #1 << 31 ; insert hidden one (even for denorms)
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BMI _ffix_negative ; If negative input, separate case
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RSBS r2, r2, #31 + SExp_bias ; Determine shift amount
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BLT shift_left ; Negative shift is a shift left, NaN,
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; or INF; zero shift is an overflow
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CMP r2, #32 ; See if shifting all bits out
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BGE shift_right_32 ; If shifting all bits out, return zero
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shift_right
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RSB r1, r2, #32 ; Check for inexact
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MOVS r1, r0, LSL r1 ; ..
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ORRNE r3, r3, #INX_bit ; ..
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MOV r0, r0, LSR r2 ; Shift the result
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B __stou_return ; Return
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shift_left
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ORR r3, r3, #IVO_bit ; Overflow so set invalid operation
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RSB r2, r2, #0 ; Get left shift amount
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MOV r0, r0, LSL r2 ; Perform shift
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B __stou_return ; Return
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shift_right_32 ; abs(Arg) < 1.0, so losing all bits
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BIC r3, r3, #IVO_bit ; Ensure invalid is clear
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MOV r0, #0 ; Return zero
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MOVS r1, r12, LSL #1 ; Check for inexact
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ORRNE r3, r3, #INX_bit ; If bits being lost, set inexact
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B __stou_return ; Return
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_ffix_negative
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ORR r3, r3, #IVO_bit ; Have a negative so invalid
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AND r2, r2, #0xFF ; Mask off exponent field
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RSBS r2, r2, #31 + SExp_bias ; Determine shift amount
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BLT shift_left_neg ; Negative shift is a shift left, NaN
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; or INF
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CMP r2, #32 ; See if shifting all bits out
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BGE shift_right_32 ; If shifting all bits out, return zero
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; note that this is not an invalid
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; operation exception
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shift_right_neg
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MOV r0, r0, LSR r2 ; Shift the result
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RSB r0, r0, #0 ; Negate result
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B __stou_return ; Return
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shift_left_neg
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RSB r2, r2, #0 ; Get left shift amount
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MOV r0, r0, LSL r2 ; Perform shift
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RSB r0, r0, #0 ; Negate result
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B __stou_return ; Return
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__stou_return
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TST r3, #FPECause_mask ; Any exceptions?
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ADDEQ sp, sp, #LOC_SIZE ; If not, restore stack and
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IF Interworking :LOR: Thumbing
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LDMEQFD sp!, {lr} ; return
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BXEQ lr
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ELSE
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LDMEQFD sp!, {pc} ; return
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ENDIF
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STR r0, [sp, #ExDResl] ; Store default result
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ADD r0, sp, #NewResl ; Pointer to new result
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MOV r1, r3 ; Exception information
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MOV r2, r12 ; Original arg
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CALL FPE_Raise ; Handle exception information
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IF Thumbing :LAND: :LNOT: Interworking
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CODE16
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bx pc ; switch back to ARM mode
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nop
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CODE32
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ENDIF
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LDR r0, [sp, #NewResl] ; Load new result
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ADD sp, sp, #LOC_SIZE ; Pop off exception record
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IF Interworking :LOR: Thumbing
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LDMFD sp!, {lr} ; Return
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BX lr
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ELSE
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LDMFD sp!, {pc} ; Return
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ENDIF
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ENTRY_END __stou
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END
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