| /* |
| * arch/alpha/lib/ev6-csum_ipv6_magic.S |
| * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> |
| * |
| * unsigned short csum_ipv6_magic(struct in6_addr *saddr, |
| * struct in6_addr *daddr, |
| * __u32 len, |
| * unsigned short proto, |
| * unsigned int csum); |
| * |
| * 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 |
| * Try not to change the actual algorithm if possible for consistency. |
| * Determining actual stalls (other than slotting) doesn't appear to be easy to do. |
| * |
| * unsigned short csum_ipv6_magic(struct in6_addr *saddr, |
| * struct in6_addr *daddr, |
| * __u32 len, |
| * unsigned short proto, |
| * unsigned int csum); |
| * |
| * Swap <proto> (takes form 0xaabb) |
| * Then shift it left by 48, so result is: |
| * 0xbbaa0000 00000000 |
| * Then turn it back into a sign extended 32-bit item |
| * 0xbbaa0000 |
| * |
| * Swap <len> (an unsigned int) using Mike Burrows' 7-instruction sequence |
| * (we can't hide the 3-cycle latency of the unpkbw in the 6-instruction sequence) |
| * Assume input takes form 0xAABBCCDD |
| * |
| * Finally, original 'folding' approach is to split the long into 4 unsigned shorts |
| * add 4 ushorts, resulting in ushort/carry |
| * add carry bits + ushort --> ushort |
| * add carry bits + ushort --> ushort (in case the carry results in an overflow) |
| * Truncate to a ushort. (took 13 instructions) |
| * From doing some testing, using the approach in checksum.c:from64to16() |
| * results in the same outcome: |
| * split into 2 uints, add those, generating a ulong |
| * add the 3 low ushorts together, generating a uint |
| * a final add of the 2 lower ushorts |
| * truncating the result. |
| * |
| * Misalignment handling added by Ivan Kokshaysky <ink@jurassic.park.msu.ru> |
| * The cost is 16 instructions (~8 cycles), including two extra loads which |
| * may cause additional delay in rare cases (load-load replay traps). |
| */ |
| |
| .globl csum_ipv6_magic |
| .align 4 |
| .ent csum_ipv6_magic |
| .frame $30,0,$26,0 |
| csum_ipv6_magic: |
| .prologue 0 |
| |
| ldq_u $0,0($16) # L : Latency: 3 |
| inslh $18,7,$4 # U : 0000000000AABBCC |
| ldq_u $1,8($16) # L : Latency: 3 |
| sll $19,8,$7 # U : U L U L : 0x00000000 00aabb00 |
| |
| and $16,7,$6 # E : src misalignment |
| ldq_u $5,15($16) # L : Latency: 3 |
| zapnot $20,15,$20 # U : zero extend incoming csum |
| ldq_u $2,0($17) # L : U L U L : Latency: 3 |
| |
| extql $0,$6,$0 # U : |
| extqh $1,$6,$22 # U : |
| ldq_u $3,8($17) # L : Latency: 3 |
| sll $19,24,$19 # U : U U L U : 0x000000aa bb000000 |
| |
| cmoveq $6,$31,$22 # E : src aligned? |
| ldq_u $23,15($17) # L : Latency: 3 |
| inswl $18,3,$18 # U : 000000CCDD000000 |
| addl $19,$7,$19 # E : U L U L : <sign bits>bbaabb00 |
| |
| or $0,$22,$0 # E : 1st src word complete |
| extql $1,$6,$1 # U : |
| or $18,$4,$18 # E : 000000CCDDAABBCC |
| extqh $5,$6,$5 # U : L U L U |
| |
| and $17,7,$6 # E : dst misalignment |
| extql $2,$6,$2 # U : |
| or $1,$5,$1 # E : 2nd src word complete |
| extqh $3,$6,$22 # U : L U L U : |
| |
| cmoveq $6,$31,$22 # E : dst aligned? |
| extql $3,$6,$3 # U : |
| addq $20,$0,$20 # E : begin summing the words |
| extqh $23,$6,$23 # U : L U L U : |
| |
| srl $18,16,$4 # U : 0000000000CCDDAA |
| or $2,$22,$2 # E : 1st dst word complete |
| zap $19,0x3,$19 # U : <sign bits>bbaa0000 |
| or $3,$23,$3 # E : U L U L : 2nd dst word complete |
| |
| cmpult $20,$0,$0 # E : |
| addq $20,$1,$20 # E : |
| zapnot $18,0xa,$18 # U : 00000000DD00BB00 |
| zap $4,0xa,$4 # U : U U L L : 0000000000CC00AA |
| |
| or $18,$4,$18 # E : 00000000DDCCBBAA |
| nop # E : |
| cmpult $20,$1,$1 # E : |
| addq $20,$2,$20 # E : U L U L |
| |
| cmpult $20,$2,$2 # E : |
| addq $20,$3,$20 # E : |
| cmpult $20,$3,$3 # E : (1 cycle stall on $20) |
| addq $20,$18,$20 # E : U L U L (1 cycle stall on $20) |
| |
| cmpult $20,$18,$18 # E : |
| addq $20,$19,$20 # E : (1 cycle stall on $20) |
| addq $0,$1,$0 # E : merge the carries back into the csum |
| addq $2,$3,$2 # E : |
| |
| cmpult $20,$19,$19 # E : |
| addq $18,$19,$18 # E : (1 cycle stall on $19) |
| addq $0,$2,$0 # E : |
| addq $20,$18,$20 # E : U L U L : |
| /* (1 cycle stall on $18, 2 cycles on $20) */ |
| |
| addq $0,$20,$0 # E : |
| zapnot $0,15,$1 # U : Start folding output (1 cycle stall on $0) |
| nop # E : |
| srl $0,32,$0 # U : U L U L : (1 cycle stall on $0) |
| |
| addq $1,$0,$1 # E : Finished generating ulong |
| extwl $1,2,$2 # U : ushort[1] (1 cycle stall on $1) |
| zapnot $1,3,$0 # U : ushort[0] (1 cycle stall on $1) |
| extwl $1,4,$1 # U : ushort[2] (1 cycle stall on $1) |
| |
| addq $0,$2,$0 # E |
| addq $0,$1,$3 # E : Finished generating uint |
| /* (1 cycle stall on $0) */ |
| extwl $3,2,$1 # U : ushort[1] (1 cycle stall on $3) |
| nop # E : L U L U |
| |
| addq $1,$3,$0 # E : Final carry |
| not $0,$4 # E : complement (1 cycle stall on $0) |
| zapnot $4,3,$0 # U : clear upper garbage bits |
| /* (1 cycle stall on $4) */ |
| ret # L0 : L U L U |
| |
| .end csum_ipv6_magic |
