| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Fast, simple, yet decent quality random number generator based on |
| 3 | * a paper by David G. Carta ("Two Fast Implementations of the |
| 4 | * `Minimal Standard' Random Number Generator," Communications of the |
| 5 | * ACM, January, 1990). |
| 6 | * |
| 7 | * Copyright (C) 2002 Hewlett-Packard Co |
| 8 | * David Mosberger-Tang <davidm@hpl.hp.com> |
| 9 | */ |
| 10 | |
| 11 | #include <asm/asmmacro.h> |
| 12 | |
| 13 | #define a r2 |
| 14 | #define m r3 |
| 15 | #define lo r8 |
| 16 | #define hi r9 |
| 17 | #define t0 r16 |
| 18 | #define t1 r17 |
| 19 | #define seed r32 |
| 20 | |
| 21 | GLOBAL_ENTRY(carta_random32) |
| 22 | movl a = (16807 << 16) | 16807 |
| 23 | ;; |
| 24 | pmpyshr2.u t0 = a, seed, 0 |
| 25 | pmpyshr2.u t1 = a, seed, 16 |
| 26 | ;; |
| 27 | unpack2.l t0 = t1, t0 |
| 28 | dep m = -1, r0, 0, 31 |
| 29 | ;; |
| 30 | zxt4 lo = t0 |
| 31 | shr.u hi = t0, 32 |
| 32 | ;; |
| 33 | dep t0 = 0, hi, 15, 49 // t0 = (hi & 0x7fff) |
| 34 | ;; |
| 35 | shl t0 = t0, 16 // t0 = (hi & 0x7fff) << 16 |
| 36 | shr t1 = hi, 15 // t1 = (hi >> 15) |
| 37 | ;; |
| 38 | add lo = lo, t0 |
| 39 | ;; |
| 40 | cmp.gtu p6, p0 = lo, m |
| 41 | ;; |
| 42 | (p6) and lo = lo, m |
| 43 | ;; |
| 44 | (p6) add lo = 1, lo |
| 45 | ;; |
| 46 | add lo = lo, t1 |
| 47 | ;; |
| 48 | cmp.gtu p6, p0 = lo, m |
| 49 | ;; |
| 50 | (p6) and lo = lo, m |
| 51 | ;; |
| 52 | (p6) add lo = 1, lo |
| 53 | br.ret.sptk.many rp |
| 54 | END(carta_random32) |