/* | |

* SHA-1 implementation for PowerPC. | |

* | |

* Copyright (C) 2005 Paul Mackerras <paulus@samba.org> | |

*/ | |

/* | |

* PowerPC calling convention: | |

* %r0 - volatile temp | |

* %r1 - stack pointer. | |

* %r2 - reserved | |

* %r3-%r12 - Incoming arguments & return values; volatile. | |

* %r13-%r31 - Callee-save registers | |

* %lr - Return address, volatile | |

* %ctr - volatile | |

* | |

* Register usage in this routine: | |

* %r0 - temp | |

* %r3 - argument (pointer to 5 words of SHA state) | |

* %r4 - argument (pointer to data to hash) | |

* %r5 - Constant K in SHA round (initially number of blocks to hash) | |

* %r6-%r10 - Working copies of SHA variables A..E (actually E..A order) | |

* %r11-%r26 - Data being hashed W[]. | |

* %r27-%r31 - Previous copies of A..E, for final add back. | |

* %ctr - loop count | |

*/ | |

/* | |

* We roll the registers for A, B, C, D, E around on each | |

* iteration; E on iteration t is D on iteration t+1, and so on. | |

* We use registers 6 - 10 for this. (Registers 27 - 31 hold | |

* the previous values.) | |

*/ | |

#define RA(t) (((t)+4)%5+6) | |

#define RB(t) (((t)+3)%5+6) | |

#define RC(t) (((t)+2)%5+6) | |

#define RD(t) (((t)+1)%5+6) | |

#define RE(t) (((t)+0)%5+6) | |

/* We use registers 11 - 26 for the W values */ | |

#define W(t) ((t)%16+11) | |

/* Register 5 is used for the constant k */ | |

/* | |

* The basic SHA-1 round function is: | |

* E += ROTL(A,5) + F(B,C,D) + W[i] + K; B = ROTL(B,30) | |

* Then the variables are renamed: (A,B,C,D,E) = (E,A,B,C,D). | |

* | |

* Every 20 rounds, the function F() and the constant K changes: | |

* - 20 rounds of f0(b,c,d) = "bit wise b ? c : d" = (^b & d) + (b & c) | |

* - 20 rounds of f1(b,c,d) = b^c^d = (b^d)^c | |

* - 20 rounds of f2(b,c,d) = majority(b,c,d) = (b&d) + ((b^d)&c) | |

* - 20 more rounds of f1(b,c,d) | |

* | |

* These are all scheduled for near-optimal performance on a G4. | |

* The G4 is a 3-issue out-of-order machine with 3 ALUs, but it can only | |

* *consider* starting the oldest 3 instructions per cycle. So to get | |

* maximum performance out of it, you have to treat it as an in-order | |

* machine. Which means interleaving the computation round t with the | |

* computation of W[t+4]. | |

* | |

* The first 16 rounds use W values loaded directly from memory, while the | |

* remaining 64 use values computed from those first 16. We preload | |

* 4 values before starting, so there are three kinds of rounds: | |

* - The first 12 (all f0) also load the W values from memory. | |

* - The next 64 compute W(i+4) in parallel. 8*f0, 20*f1, 20*f2, 16*f1. | |

* - The last 4 (all f1) do not do anything with W. | |

* | |

* Therefore, we have 6 different round functions: | |

* STEPD0_LOAD(t,s) - Perform round t and load W(s). s < 16 | |

* STEPD0_UPDATE(t,s) - Perform round t and compute W(s). s >= 16. | |

* STEPD1_UPDATE(t,s) | |

* STEPD2_UPDATE(t,s) | |

* STEPD1(t) - Perform round t with no load or update. | |

* | |

* The G5 is more fully out-of-order, and can find the parallelism | |

* by itself. The big limit is that it has a 2-cycle ALU latency, so | |

* even though it's 2-way, the code has to be scheduled as if it's | |

* 4-way, which can be a limit. To help it, we try to schedule the | |

* read of RA(t) as late as possible so it doesn't stall waiting for | |

* the previous round's RE(t-1), and we try to rotate RB(t) as early | |

* as possible while reading RC(t) (= RB(t-1)) as late as possible. | |

*/ | |

/* the initial loads. */ | |

#define LOADW(s) \ | |

lwz W(s),(s)*4(%r4) | |

/* | |

* Perform a step with F0, and load W(s). Uses W(s) as a temporary | |

* before loading it. | |

* This is actually 10 instructions, which is an awkward fit. | |

* It can execute grouped as listed, or delayed one instruction. | |

* (If delayed two instructions, there is a stall before the start of the | |

* second line.) Thus, two iterations take 7 cycles, 3.5 cycles per round. | |

*/ | |

#define STEPD0_LOAD(t,s) \ | |

add RE(t),RE(t),W(t); andc %r0,RD(t),RB(t); and W(s),RC(t),RB(t); \ | |

add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; rotlwi RB(t),RB(t),30; \ | |

add RE(t),RE(t),W(s); add %r0,%r0,%r5; lwz W(s),(s)*4(%r4); \ | |

add RE(t),RE(t),%r0 | |

/* | |

* This is likewise awkward, 13 instructions. However, it can also | |

* execute starting with 2 out of 3 possible moduli, so it does 2 rounds | |

* in 9 cycles, 4.5 cycles/round. | |

*/ | |

#define STEPD0_UPDATE(t,s,loadk...) \ | |

add RE(t),RE(t),W(t); andc %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \ | |

add RE(t),RE(t),%r0; and %r0,RC(t),RB(t); xor W(s),W(s),W((s)-8); \ | |

add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; xor W(s),W(s),W((s)-14); \ | |

add RE(t),RE(t),%r5; loadk; rotlwi RB(t),RB(t),30; rotlwi W(s),W(s),1; \ | |

add RE(t),RE(t),%r0 | |

/* Nicely optimal. Conveniently, also the most common. */ | |

#define STEPD1_UPDATE(t,s,loadk...) \ | |

add RE(t),RE(t),W(t); xor %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \ | |

add RE(t),RE(t),%r5; loadk; xor %r0,%r0,RC(t); xor W(s),W(s),W((s)-8); \ | |

add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; xor W(s),W(s),W((s)-14); \ | |

add RE(t),RE(t),%r0; rotlwi RB(t),RB(t),30; rotlwi W(s),W(s),1 | |

/* | |

* The naked version, no UPDATE, for the last 4 rounds. 3 cycles per. | |

* We could use W(s) as a temp register, but we don't need it. | |

*/ | |

#define STEPD1(t) \ | |

add RE(t),RE(t),W(t); xor %r0,RD(t),RB(t); \ | |

rotlwi RB(t),RB(t),30; add RE(t),RE(t),%r5; xor %r0,%r0,RC(t); \ | |

add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; /* spare slot */ \ | |

add RE(t),RE(t),%r0 | |

/* | |

* 14 instructions, 5 cycles per. The majority function is a bit | |

* awkward to compute. This can execute with a 1-instruction delay, | |

* but it causes a 2-instruction delay, which triggers a stall. | |

*/ | |

#define STEPD2_UPDATE(t,s,loadk...) \ | |

add RE(t),RE(t),W(t); and %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \ | |

add RE(t),RE(t),%r0; xor %r0,RD(t),RB(t); xor W(s),W(s),W((s)-8); \ | |

add RE(t),RE(t),%r5; loadk; and %r0,%r0,RC(t); xor W(s),W(s),W((s)-14); \ | |

add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; rotlwi W(s),W(s),1; \ | |

add RE(t),RE(t),%r0; rotlwi RB(t),RB(t),30 | |

#define STEP0_LOAD4(t,s) \ | |

STEPD0_LOAD(t,s); \ | |

STEPD0_LOAD((t+1),(s)+1); \ | |

STEPD0_LOAD((t)+2,(s)+2); \ | |

STEPD0_LOAD((t)+3,(s)+3) | |

#define STEPUP4(fn, t, s, loadk...) \ | |

STEP##fn##_UPDATE(t,s,); \ | |

STEP##fn##_UPDATE((t)+1,(s)+1,); \ | |

STEP##fn##_UPDATE((t)+2,(s)+2,); \ | |

STEP##fn##_UPDATE((t)+3,(s)+3,loadk) | |

#define STEPUP20(fn, t, s, loadk...) \ | |

STEPUP4(fn, t, s,); \ | |

STEPUP4(fn, (t)+4, (s)+4,); \ | |

STEPUP4(fn, (t)+8, (s)+8,); \ | |

STEPUP4(fn, (t)+12, (s)+12,); \ | |

STEPUP4(fn, (t)+16, (s)+16, loadk) | |

.globl sha1_core | |

sha1_core: | |

stwu %r1,-80(%r1) | |

stmw %r13,4(%r1) | |

/* Load up A - E */ | |

lmw %r27,0(%r3) | |

mtctr %r5 | |

1: | |

LOADW(0) | |

lis %r5,0x5a82 | |

mr RE(0),%r31 | |

LOADW(1) | |

mr RD(0),%r30 | |

mr RC(0),%r29 | |

LOADW(2) | |

ori %r5,%r5,0x7999 /* K0-19 */ | |

mr RB(0),%r28 | |

LOADW(3) | |

mr RA(0),%r27 | |

STEP0_LOAD4(0, 4) | |

STEP0_LOAD4(4, 8) | |

STEP0_LOAD4(8, 12) | |

STEPUP4(D0, 12, 16,) | |

STEPUP4(D0, 16, 20, lis %r5,0x6ed9) | |

ori %r5,%r5,0xeba1 /* K20-39 */ | |

STEPUP20(D1, 20, 24, lis %r5,0x8f1b) | |

ori %r5,%r5,0xbcdc /* K40-59 */ | |

STEPUP20(D2, 40, 44, lis %r5,0xca62) | |

ori %r5,%r5,0xc1d6 /* K60-79 */ | |

STEPUP4(D1, 60, 64,) | |

STEPUP4(D1, 64, 68,) | |

STEPUP4(D1, 68, 72,) | |

STEPUP4(D1, 72, 76,) | |

addi %r4,%r4,64 | |

STEPD1(76) | |

STEPD1(77) | |

STEPD1(78) | |

STEPD1(79) | |

/* Add results to original values */ | |

add %r31,%r31,RE(0) | |

add %r30,%r30,RD(0) | |

add %r29,%r29,RC(0) | |

add %r28,%r28,RB(0) | |

add %r27,%r27,RA(0) | |

bdnz 1b | |

/* Save final hash, restore registers, and return */ | |

stmw %r27,0(%r3) | |

lmw %r13,4(%r1) | |

addi %r1,%r1,80 | |

blr |