1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
127 lines
4.3 KiB
ArmAsm
127 lines
4.3 KiB
ArmAsm
/*
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* arch/alpha/lib/ev6-csum_ipv6_magic.S
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* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
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*
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* unsigned short csum_ipv6_magic(struct in6_addr *saddr,
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* struct in6_addr *daddr,
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* __u32 len,
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* unsigned short proto,
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* unsigned int csum);
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*
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* Much of the information about 21264 scheduling/coding comes from:
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* Compiler Writer's Guide for the Alpha 21264
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* abbreviated as 'CWG' in other comments here
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* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
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* Scheduling notation:
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* E - either cluster
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* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
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* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
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* Try not to change the actual algorithm if possible for consistency.
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* Determining actual stalls (other than slotting) doesn't appear to be easy to do.
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*
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* unsigned short csum_ipv6_magic(struct in6_addr *saddr,
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* struct in6_addr *daddr,
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* __u32 len,
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* unsigned short proto,
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* unsigned int csum);
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*
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* Swap <proto> (takes form 0xaabb)
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* Then shift it left by 48, so result is:
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* 0xbbaa0000 00000000
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* Then turn it back into a sign extended 32-bit item
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* 0xbbaa0000
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*
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* Swap <len> (an unsigned int) using Mike Burrows' 7-instruction sequence
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* (we can't hide the 3-cycle latency of the unpkbw in the 6-instruction sequence)
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* Assume input takes form 0xAABBCCDD
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*
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* Finally, original 'folding' approach is to split the long into 4 unsigned shorts
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* add 4 ushorts, resulting in ushort/carry
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* add carry bits + ushort --> ushort
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* add carry bits + ushort --> ushort (in case the carry results in an overflow)
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* Truncate to a ushort. (took 13 instructions)
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* From doing some testing, using the approach in checksum.c:from64to16()
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* results in the same outcome:
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* split into 2 uints, add those, generating a ulong
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* add the 3 low ushorts together, generating a uint
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* a final add of the 2 lower ushorts
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* truncating the result.
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*/
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.globl csum_ipv6_magic
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.align 4
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.ent csum_ipv6_magic
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.frame $30,0,$26,0
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csum_ipv6_magic:
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.prologue 0
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ldq $0,0($16) # L : Latency: 3
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inslh $18,7,$4 # U : 0000000000AABBCC
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ldq $1,8($16) # L : Latency: 3
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sll $19,8,$7 # U : U L U L : 0x00000000 00aabb00
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zapnot $20,15,$20 # U : zero extend incoming csum
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ldq $2,0($17) # L : Latency: 3
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sll $19,24,$19 # U : U L L U : 0x000000aa bb000000
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inswl $18,3,$18 # U : 000000CCDD000000
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ldq $3,8($17) # L : Latency: 3
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bis $18,$4,$18 # E : 000000CCDDAABBCC
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addl $19,$7,$19 # E : <sign bits>bbaabb00
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nop # E : U L U L
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addq $20,$0,$20 # E : begin summing the words
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srl $18,16,$4 # U : 0000000000CCDDAA
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zap $19,0x3,$19 # U : <sign bits>bbaa0000
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nop # E : L U U L
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cmpult $20,$0,$0 # E :
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addq $20,$1,$20 # E :
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zapnot $18,0xa,$18 # U : 00000000DD00BB00
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zap $4,0xa,$4 # U : U U L L : 0000000000CC00AA
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or $18,$4,$18 # E : 00000000DDCCBBAA
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nop # E :
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cmpult $20,$1,$1 # E :
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addq $20,$2,$20 # E : U L U L
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cmpult $20,$2,$2 # E :
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addq $20,$3,$20 # E :
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cmpult $20,$3,$3 # E : (1 cycle stall on $20)
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addq $20,$18,$20 # E : U L U L (1 cycle stall on $20)
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cmpult $20,$18,$18 # E :
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addq $20,$19,$20 # E : (1 cycle stall on $20)
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addq $0,$1,$0 # E : merge the carries back into the csum
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addq $2,$3,$2 # E :
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cmpult $20,$19,$19 # E :
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addq $18,$19,$18 # E : (1 cycle stall on $19)
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addq $0,$2,$0 # E :
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addq $20,$18,$20 # E : U L U L :
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/* (1 cycle stall on $18, 2 cycles on $20) */
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addq $0,$20,$0 # E :
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zapnot $0,15,$1 # U : Start folding output (1 cycle stall on $0)
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nop # E :
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srl $0,32,$0 # U : U L U L : (1 cycle stall on $0)
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addq $1,$0,$1 # E : Finished generating ulong
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extwl $1,2,$2 # U : ushort[1] (1 cycle stall on $1)
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zapnot $1,3,$0 # U : ushort[0] (1 cycle stall on $1)
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extwl $1,4,$1 # U : ushort[2] (1 cycle stall on $1)
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addq $0,$2,$0 # E
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addq $0,$1,$3 # E : Finished generating uint
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/* (1 cycle stall on $0) */
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extwl $3,2,$1 # U : ushort[1] (1 cycle stall on $3)
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nop # E : L U L U
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addq $1,$3,$0 # E : Final carry
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not $0,$4 # E : complement (1 cycle stall on $0)
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zapnot $4,3,$0 # U : clear upper garbage bits
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/* (1 cycle stall on $4) */
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ret # L0 : L U L U
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.end csum_ipv6_magic
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