diff options
Diffstat (limited to 'arch/alpha/lib/ev6-csum_ipv6_magic.S')
| -rw-r--r-- | arch/alpha/lib/ev6-csum_ipv6_magic.S | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev6-csum_ipv6_magic.S b/arch/alpha/lib/ev6-csum_ipv6_magic.S new file mode 100644 index 0000000..de1948a --- /dev/null +++ b/arch/alpha/lib/ev6-csum_ipv6_magic.S @@ -0,0 +1,126 @@ +/* + * 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. + */ + + .globl csum_ipv6_magic + .align 4 + .ent csum_ipv6_magic + .frame $30,0,$26,0 +csum_ipv6_magic: + .prologue 0 + + ldq $0,0($16) # L : Latency: 3 + inslh $18,7,$4 # U : 0000000000AABBCC + ldq $1,8($16) # L : Latency: 3 + sll $19,8,$7 # U : U L U L : 0x00000000 00aabb00 + + zapnot $20,15,$20 # U : zero extend incoming csum + ldq $2,0($17) # L : Latency: 3 + sll $19,24,$19 # U : U L L U : 0x000000aa bb000000 + inswl $18,3,$18 # U : 000000CCDD000000 + + ldq $3,8($17) # L : Latency: 3 + bis $18,$4,$18 # E : 000000CCDDAABBCC + addl $19,$7,$19 # E : <sign bits>bbaabb00 + nop # E : U L U L + + addq $20,$0,$20 # E : begin summing the words + srl $18,16,$4 # U : 0000000000CCDDAA + zap $19,0x3,$19 # U : <sign bits>bbaa0000 + nop # E : L U U L + + 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 |
