mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
227 lines
6.9 KiB
227 lines
6.9 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
|
/* |
|
* arch/alpha/lib/ev6-copy_user.S |
|
* |
|
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> |
|
* |
|
* Copy to/from user space, handling exceptions as we go.. This |
|
* isn't exactly pretty. |
|
* |
|
* This is essentially the same as "memcpy()", but with a few twists. |
|
* Notably, we have to make sure that $0 is always up-to-date and |
|
* contains the right "bytes left to copy" value (and that it is updated |
|
* only _after_ a successful copy). There is also some rather minor |
|
* exception setup stuff.. |
|
* |
|
* Much of the information about 21264 scheduling/coding comes from: |
|
* Compiler Writer's Guide for the Alpha 21264 |
|
* abbreviated as 'CWG' in other comments here |
|
* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html |
|
* Scheduling notation: |
|
* E - either cluster |
|
* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 |
|
* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 |
|
*/ |
|
|
|
#include <asm/export.h> |
|
/* Allow an exception for an insn; exit if we get one. */ |
|
#define EXI(x,y...) \ |
|
99: x,##y; \ |
|
.section __ex_table,"a"; \ |
|
.long 99b - .; \ |
|
lda $31, $exitin-99b($31); \ |
|
.previous |
|
|
|
#define EXO(x,y...) \ |
|
99: x,##y; \ |
|
.section __ex_table,"a"; \ |
|
.long 99b - .; \ |
|
lda $31, $exitout-99b($31); \ |
|
.previous |
|
|
|
.set noat |
|
.align 4 |
|
.globl __copy_user |
|
.ent __copy_user |
|
# Pipeline info: Slotting & Comments |
|
__copy_user: |
|
.prologue 0 |
|
mov $18, $0 # .. .. .. E |
|
subq $18, 32, $1 # .. .. E. .. : Is this going to be a small copy? |
|
nop # .. E .. .. |
|
beq $18, $zerolength # U .. .. .. : U L U L |
|
|
|
and $16,7,$3 # .. .. .. E : is leading dest misalignment |
|
ble $1, $onebyteloop # .. .. U .. : 1st branch : small amount of data |
|
beq $3, $destaligned # .. U .. .. : 2nd (one cycle fetcher stall) |
|
subq $3, 8, $3 # E .. .. .. : L U U L : trip counter |
|
/* |
|
* The fetcher stall also hides the 1 cycle cross-cluster stall for $3 (L --> U) |
|
* This loop aligns the destination a byte at a time |
|
* We know we have at least one trip through this loop |
|
*/ |
|
$aligndest: |
|
EXI( ldbu $1,0($17) ) # .. .. .. L : Keep loads separate from stores |
|
addq $16,1,$16 # .. .. E .. : Section 3.8 in the CWG |
|
addq $3,1,$3 # .. E .. .. : |
|
nop # E .. .. .. : U L U L |
|
|
|
/* |
|
* the -1 is to compensate for the inc($16) done in a previous quadpack |
|
* which allows us zero dependencies within either quadpack in the loop |
|
*/ |
|
EXO( stb $1,-1($16) ) # .. .. .. L : |
|
addq $17,1,$17 # .. .. E .. : Section 3.8 in the CWG |
|
subq $0,1,$0 # .. E .. .. : |
|
bne $3, $aligndest # U .. .. .. : U L U L |
|
|
|
/* |
|
* If we fell through into here, we have a minimum of 33 - 7 bytes |
|
* If we arrived via branch, we have a minimum of 32 bytes |
|
*/ |
|
$destaligned: |
|
and $17,7,$1 # .. .. .. E : Check _current_ source alignment |
|
bic $0,7,$4 # .. .. E .. : number bytes as a quadword loop |
|
EXI( ldq_u $3,0($17) ) # .. L .. .. : Forward fetch for fallthrough code |
|
beq $1,$quadaligned # U .. .. .. : U L U L |
|
|
|
/* |
|
* In the worst case, we've just executed an ldq_u here from 0($17) |
|
* and we'll repeat it once if we take the branch |
|
*/ |
|
|
|
/* Misaligned quadword loop - not unrolled. Leave it that way. */ |
|
$misquad: |
|
EXI( ldq_u $2,8($17) ) # .. .. .. L : |
|
subq $4,8,$4 # .. .. E .. : |
|
extql $3,$17,$3 # .. U .. .. : |
|
extqh $2,$17,$1 # U .. .. .. : U U L L |
|
|
|
bis $3,$1,$1 # .. .. .. E : |
|
EXO( stq $1,0($16) ) # .. .. L .. : |
|
addq $17,8,$17 # .. E .. .. : |
|
subq $0,8,$0 # E .. .. .. : U L L U |
|
|
|
addq $16,8,$16 # .. .. .. E : |
|
bis $2,$2,$3 # .. .. E .. : |
|
nop # .. E .. .. : |
|
bne $4,$misquad # U .. .. .. : U L U L |
|
|
|
nop # .. .. .. E |
|
nop # .. .. E .. |
|
nop # .. E .. .. |
|
beq $0,$zerolength # U .. .. .. : U L U L |
|
|
|
/* We know we have at least one trip through the byte loop */ |
|
EXI ( ldbu $2,0($17) ) # .. .. .. L : No loads in the same quad |
|
addq $16,1,$16 # .. .. E .. : as the store (Section 3.8 in CWG) |
|
nop # .. E .. .. : |
|
br $31, $dirtyentry # L0 .. .. .. : L U U L |
|
/* Do the trailing byte loop load, then hop into the store part of the loop */ |
|
|
|
/* |
|
* A minimum of (33 - 7) bytes to do a quad at a time. |
|
* Based upon the usage context, it's worth the effort to unroll this loop |
|
* $0 - number of bytes to be moved |
|
* $4 - number of bytes to move as quadwords |
|
* $16 is current destination address |
|
* $17 is current source address |
|
*/ |
|
$quadaligned: |
|
subq $4, 32, $2 # .. .. .. E : do not unroll for small stuff |
|
nop # .. .. E .. |
|
nop # .. E .. .. |
|
blt $2, $onequad # U .. .. .. : U L U L |
|
|
|
/* |
|
* There is a significant assumption here that the source and destination |
|
* addresses differ by more than 32 bytes. In this particular case, a |
|
* sparsity of registers further bounds this to be a minimum of 8 bytes. |
|
* But if this isn't met, then the output result will be incorrect. |
|
* Furthermore, due to a lack of available registers, we really can't |
|
* unroll this to be an 8x loop (which would enable us to use the wh64 |
|
* instruction memory hint instruction). |
|
*/ |
|
$unroll4: |
|
EXI( ldq $1,0($17) ) # .. .. .. L |
|
EXI( ldq $2,8($17) ) # .. .. L .. |
|
subq $4,32,$4 # .. E .. .. |
|
nop # E .. .. .. : U U L L |
|
|
|
addq $17,16,$17 # .. .. .. E |
|
EXO( stq $1,0($16) ) # .. .. L .. |
|
EXO( stq $2,8($16) ) # .. L .. .. |
|
subq $0,16,$0 # E .. .. .. : U L L U |
|
|
|
addq $16,16,$16 # .. .. .. E |
|
EXI( ldq $1,0($17) ) # .. .. L .. |
|
EXI( ldq $2,8($17) ) # .. L .. .. |
|
subq $4, 32, $3 # E .. .. .. : U U L L : is there enough for another trip? |
|
|
|
EXO( stq $1,0($16) ) # .. .. .. L |
|
EXO( stq $2,8($16) ) # .. .. L .. |
|
subq $0,16,$0 # .. E .. .. |
|
addq $17,16,$17 # E .. .. .. : U L L U |
|
|
|
nop # .. .. .. E |
|
nop # .. .. E .. |
|
addq $16,16,$16 # .. E .. .. |
|
bgt $3,$unroll4 # U .. .. .. : U L U L |
|
|
|
nop |
|
nop |
|
nop |
|
beq $4, $noquads |
|
|
|
$onequad: |
|
EXI( ldq $1,0($17) ) |
|
subq $4,8,$4 |
|
addq $17,8,$17 |
|
nop |
|
|
|
EXO( stq $1,0($16) ) |
|
subq $0,8,$0 |
|
addq $16,8,$16 |
|
bne $4,$onequad |
|
|
|
$noquads: |
|
nop |
|
nop |
|
nop |
|
beq $0,$zerolength |
|
|
|
/* |
|
* For small copies (or the tail of a larger copy), do a very simple byte loop. |
|
* There's no point in doing a lot of complex alignment calculations to try to |
|
* to quadword stuff for a small amount of data. |
|
* $0 - remaining number of bytes left to copy |
|
* $16 - current dest addr |
|
* $17 - current source addr |
|
*/ |
|
|
|
$onebyteloop: |
|
EXI ( ldbu $2,0($17) ) # .. .. .. L : No loads in the same quad |
|
addq $16,1,$16 # .. .. E .. : as the store (Section 3.8 in CWG) |
|
nop # .. E .. .. : |
|
nop # E .. .. .. : U L U L |
|
|
|
$dirtyentry: |
|
/* |
|
* the -1 is to compensate for the inc($16) done in a previous quadpack |
|
* which allows us zero dependencies within either quadpack in the loop |
|
*/ |
|
EXO ( stb $2,-1($16) ) # .. .. .. L : |
|
addq $17,1,$17 # .. .. E .. : quadpack as the load |
|
subq $0,1,$0 # .. E .. .. : change count _after_ copy |
|
bgt $0,$onebyteloop # U .. .. .. : U L U L |
|
|
|
$zerolength: |
|
$exitin: |
|
$exitout: # Destination for exception recovery(?) |
|
nop # .. .. .. E |
|
nop # .. .. E .. |
|
nop # .. E .. .. |
|
ret $31,($26),1 # L0 .. .. .. : L U L U |
|
|
|
.end __copy_user |
|
EXPORT_SYMBOL(__copy_user)
|
|
|