| /* |
| * Written by Wilco Dijkstra, 1996. The following email exchange establishes the |
| * license. |
| * |
| * From: Wilco Dijkstra <Wilco.Dijkstra@ntlworld.com> |
| * Date: Fri, Jun 24, 2011 at 3:20 AM |
| * Subject: Re: sqrt routine |
| * To: Kevin Ma <kma@google.com> |
| * Hi Kevin, |
| * Thanks for asking. Those routines are public domain (originally posted to |
| * comp.sys.arm a long time ago), so you can use them freely for any purpose. |
| * Cheers, |
| * Wilco |
| * |
| * ----- Original Message ----- |
| * From: "Kevin Ma" <kma@google.com> |
| * To: <Wilco.Dijkstra@ntlworld.com> |
| * Sent: Thursday, June 23, 2011 11:44 PM |
| * Subject: Fwd: sqrt routine |
| * Hi Wilco, |
| * I saw your sqrt routine from several web sites, including |
| * http://www.finesse.demon.co.uk/steven/sqrt.html. |
| * Just wonder if there's any copyright information with your Successive |
| * approximation routines, or if I can freely use it for any purpose. |
| * Thanks. |
| * Kevin |
| */ |
| |
| // Minor modifications in code style for WebRTC, 2012. |
| // Code optimizations for MIPS, 2013. |
| |
| #include "common_audio/signal_processing/include/signal_processing_library.h" |
| |
| /* |
| * Algorithm: |
| * Successive approximation of the equation (root + delta) ^ 2 = N |
| * until delta < 1. If delta < 1 we have the integer part of SQRT (N). |
| * Use delta = 2^i for i = 15 .. 0. |
| * |
| * Output precision is 16 bits. Note for large input values (close to |
| * 0x7FFFFFFF), bit 15 (the highest bit of the low 16-bit half word) |
| * contains the MSB information (a non-sign value). Do with caution |
| * if you need to cast the output to int16_t type. |
| * |
| * If the input value is negative, it returns 0. |
| */ |
| |
| |
| int32_t WebRtcSpl_SqrtFloor(int32_t value) |
| { |
| int32_t root = 0, tmp1, tmp2, tmp3, tmp4; |
| |
| __asm __volatile( |
| ".set push \n\t" |
| ".set noreorder \n\t" |
| |
| "lui %[tmp1], 0x4000 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "sub %[tmp3], %[value], %[tmp1] \n\t" |
| "lui %[tmp1], 0x1 \n\t" |
| "or %[tmp4], %[root], %[tmp1] \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x4000 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 14 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x8000 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x2000 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 13 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x4000 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x1000 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 12 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x2000 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x800 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 11 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x1000 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x400 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 10 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x800 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x200 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 9 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x400 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x100 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 8 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x200 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x80 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 7 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x100 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x40 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 6 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x80 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x20 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 5 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x40 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x10 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 4 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x20 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x8 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 3 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x10 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x4 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 2 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x8 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x2 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "sll %[tmp1], 1 \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "subu %[tmp3], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x4 \n\t" |
| "movz %[value], %[tmp3], %[tmp2] \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| "addiu %[tmp1], $0, 0x1 \n\t" |
| "addu %[tmp1], %[tmp1], %[root] \n\t" |
| "slt %[tmp2], %[value], %[tmp1] \n\t" |
| "ori %[tmp4], %[root], 0x2 \n\t" |
| "movz %[root], %[tmp4], %[tmp2] \n\t" |
| |
| ".set pop \n\t" |
| |
| : [root] "+r" (root), [value] "+r" (value), |
| [tmp1] "=&r" (tmp1), [tmp2] "=&r" (tmp2), |
| [tmp3] "=&r" (tmp3), [tmp4] "=&r" (tmp4) |
| : |
| ); |
| |
| return root >> 1; |
| } |
| |
