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! Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
! Imagination Technologies Ltd
!
! Integer divide routines.
!
.text
.global ___udivsi3
.type ___udivsi3,function
.align 2
___udivsi3:
!!
!! Since core is signed divide case, just set control variable
!!
MOV D1Re0,D0Ar2 ! Au already in A1Ar1, Bu -> D1Re0
MOV D0Re0,#0 ! Result is 0
MOV D0Ar4,#0 ! Return positive result
B $LIDMCUStart
.size ___udivsi3,.-___udivsi3
!!
!! 32-bit division signed i/p - passed signed 32-bit numbers
!!
.global ___divsi3
.type ___divsi3,function
.align 2
___divsi3:
!!
!! A already in D1Ar1, B already in D0Ar2 -> make B abs(B)
!!
MOV D1Re0,D0Ar2 ! A already in A1Ar1, B -> D1Re0
MOV D0Re0,#0 ! Result is 0
XOR D0Ar4,D1Ar1,D1Re0 ! D0Ar4 -ive if result is -ive
ABS D1Ar1,D1Ar1 ! abs(A) -> Au
ABS D1Re0,D1Re0 ! abs(B) -> Bu
$LIDMCUStart:
CMP D1Ar1,D1Re0 ! Is ( Au > Bu )?
LSR D1Ar3,D1Ar1,#2 ! Calculate (Au & (~3)) >> 2
CMPHI D1Re0,D1Ar3 ! OR ( (Au & (~3)) <= (Bu << 2) )?
LSLSHI D1Ar3,D1Re0,#1 ! Buq = Bu << 1
BLS $LIDMCUSetup ! Yes: Do normal divide
!!
!! Quick divide setup can assume that CurBit only needs to start at 2
!!
$LIDMCQuick:
CMP D1Ar1,D1Ar3 ! ( A >= Buq )?
ADDCC D0Re0,D0Re0,#2 ! If yes result += 2
SUBCC D1Ar1,D1Ar1,D1Ar3 ! and A -= Buq
CMP D1Ar1,D1Re0 ! ( A >= Bu )?
ADDCC D0Re0,D0Re0,#1 ! If yes result += 1
SUBCC D1Ar1,D1Ar1,D1Re0 ! and A -= Bu
ORS D0Ar4,D0Ar4,D0Ar4 ! Return neg result?
NEG D0Ar2,D0Re0 ! Calculate neg result
MOVMI D0Re0,D0Ar2 ! Yes: Take neg result
$LIDMCRet:
MOV PC,D1RtP
!!
!! Setup for general unsigned divide code
!!
!! D0Re0 is used to form the result, already set to Zero
!! D1Re0 is the input Bu value, this gets trashed
!! D0Ar6 is curbit which is set to 1 at the start and shifted up
!! D0Ar4 is negative if we should return a negative result
!! D1Ar1 is the input Au value, eventually this holds the remainder
!!
$LIDMCUSetup:
CMP D1Ar1,D1Re0 ! Is ( Au < Bu )?
MOV D0Ar6,#1 ! Set curbit to 1
BCS $LIDMCRet ! Yes: Return 0 remainder Au
!!
!! Calculate alignment using FFB instruction
!!
FFB D1Ar5,D1Ar1 ! Find first bit of Au
ANDN D1Ar5,D1Ar5,#31 ! Handle exceptional case.
ORN D1Ar5,D1Ar5,#31 ! if N bit set, set to 31
FFB D1Ar3,D1Re0 ! Find first bit of Bu
ANDN D1Ar3,D1Ar3,#31 ! Handle exceptional case.
ORN D1Ar3,D1Ar3,#31 ! if N bit set, set to 31
SUBS D1Ar3,D1Ar5,D1Ar3 ! calculate diff, ffbA - ffbB
MOV D0Ar2,D1Ar3 ! copy into bank 0
LSLGT D1Re0,D1Re0,D1Ar3 ! ( > 0) ? left shift B
LSLGT D0Ar6,D0Ar6,D0Ar2 ! ( > 0) ? left shift curbit
!!
!! Now we start the divide proper, logic is
!!
!! if ( A >= B ) add curbit to result and subtract B from A
!! shift curbit and B down by 1 in either case
!!
$LIDMCLoop:
CMP D1Ar1, D1Re0 ! ( A >= B )?
ADDCC D0Re0, D0Re0, D0Ar6 ! If yes result += curbit
SUBCC D1Ar1, D1Ar1, D1Re0 ! and A -= B
LSRS D0Ar6, D0Ar6, #1 ! Shift down curbit, is it zero?
LSR D1Re0, D1Re0, #1 ! Shift down B
BNZ $LIDMCLoop ! Was single bit in curbit lost?
ORS D0Ar4,D0Ar4,D0Ar4 ! Return neg result?
NEG D0Ar2,D0Re0 ! Calculate neg result
MOVMI D0Re0,D0Ar2 ! Yes: Take neg result
MOV PC,D1RtP
.size ___divsi3,.-___divsi3
|
