Optimized sqrt() for ARM.
Merged optimized sqrt() function from webRTC svn rev r1627 to improve performance ARM. Change-Id: Ie9c57e2a3b8a0786c0169028c0940184b7c9db5e
This commit is contained in:
Eric Laurent
36
NOTICE
36
NOTICE
@ -164,3 +164,39 @@ Scott McMurray
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// release() added in by Google. Use this to conditionally
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// transfer ownership of a heap-allocated object to the caller, usually on
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// method success.
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===============================================================================
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/*
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* Written by Wilco Dijkstra, 1996.
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* Refer to NOTICE file at the root of git project.
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*
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* Minor modifications in code style for WebRTC, 2012.
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*/
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// The following email record is related to source files spl_sqrt_floor.c
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// and spl_sqrt_floor.s in trunk/src/common_audio/signal_processing/.
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//
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//
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// From: Wilco Dijkstra <Wilco.Dijkstra@ntlworld.com>
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// Date: Fri, Jun 24, 2011 at 3:20 AM
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// Subject: Re: sqrt routine
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// To: Kevin Ma <kma@google.com>
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// Hi Kevin,
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// Thanks for asking. Those routines are public domain (originally posted to
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// comp.sys.arm a long time ago), so you can use them freely for any purpose.
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// Cheers,
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// Wilco
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//
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// ----- Original Message -----
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// From: "Kevin Ma" <kma@google.com>
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// To: <Wilco.Dijkstra@ntlworld.com>
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// Sent: Thursday, June 23, 2011 11:44 PM
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// Subject: Fwd: sqrt routine
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// Hi Wilco,
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// I saw your sqrt routine from several web sites, including
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// http://www.finesse.demon.co.uk/steven/sqrt.html.
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// Just wonder if there's any copyright information with your Successive
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// approximation routines, or if I can freely use it for any purpose.
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// Thanks.
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// Kevin
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@ -44,7 +44,6 @@ LOCAL_SRC_FILES := \
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resample_by_2_internal.c \
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resample_fractional.c \
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spl_sqrt.c \
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spl_sqrt_floor.c \
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spl_version.c \
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splitting_filter.c \
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sqrt_of_one_minus_x_squared.c \
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@ -65,6 +64,14 @@ LOCAL_CFLAGS += \
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$(MY_ARM_CFLAGS_NEON)
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endif
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ifeq ($(TARGET_ARCH),arm)
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LOCAL_SRC_FILES += \
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spl_sqrt_floor.s
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else
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LOCAL_SRC_FILES += \
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spl_sqrt_floor.c
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endif
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LOCAL_SHARED_LIBRARIES := libstlport
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ifeq ($(TARGET_OS)-$(TARGET_SIMULATOR),linux-true)
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@ -1,21 +1,26 @@
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/*
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* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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/*
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* This file contains the function WebRtcSpl_SqrtFloor().
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* The description header can be found in signal_processing_library.h
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* Written by Wilco Dijkstra, 1996.
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* Refer to NOTICE file at the root of git project.
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*
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* Minor modifications in code style for WebRTC, 2012.
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*/
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#include "signal_processing_library.h"
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/*
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* Algorithm:
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* Successive approximation of the equation (root + delta) ^ 2 = N
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* until delta < 1. If delta < 1 we have the integer part of SQRT (N).
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* Use delta = 2^i for i = 15 .. 0.
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*
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* Output precision is 16 bits. Note for large input values (close to
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* 0x7FFFFFFF), bit 15 (the highest bit of the low 16-bit half word)
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* contains the MSB information (a non-sign value). Do with caution
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* if you need to cast the output to int16_t type.
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*
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* If the input value is negative, it returns 0.
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*/
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#define WEBRTC_SPL_SQRT_ITER(N) \
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try1 = root + (1 << (N)); \
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if (value >= try1 << (N)) \
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@ -24,13 +29,9 @@
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root |= 2 << (N); \
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}
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// (out) Square root of input parameter
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WebRtc_Word32 WebRtcSpl_SqrtFloor(WebRtc_Word32 value)
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int32_t WebRtcSpl_SqrtFloor(int32_t value)
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{
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// new routine for performance, 4 cycles/bit in ARM
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// output precision is 16 bits
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WebRtc_Word32 root = 0, try1;
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int32_t root = 0, try1;
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WEBRTC_SPL_SQRT_ITER (15);
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WEBRTC_SPL_SQRT_ITER (14);
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88
src/common_audio/signal_processing/spl_sqrt_floor.s
Normal file
88
src/common_audio/signal_processing/spl_sqrt_floor.s
Normal file
@ -0,0 +1,88 @@
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@ Written by Wilco Dijkstra, 1996.
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@ Refer to NOTICE file at the root of git project.
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@
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@ Minor modifications in code style for WebRTC, 2012.
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@ Output is bit-exact with the reference C code in spl_sqrt_floor.c.
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@ Input : r0 32 bit unsigned integer
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@ Output: r0 = INT (SQRT (r0)), precision is 16 bits
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@ Registers touched: r1, r2
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.global WebRtcSpl_SqrtFloor
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.align 2
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WebRtcSpl_SqrtFloor:
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.fnstart
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mov r1, #3 << 30
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mov r2, #1 << 30
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@ unroll for i = 0 .. 15
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cmp r0, r2, ror #2 * 0
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subhs r0, r0, r2, ror #2 * 0
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 1
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subhs r0, r0, r2, ror #2 * 1
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 2
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subhs r0, r0, r2, ror #2 * 2
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 3
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subhs r0, r0, r2, ror #2 * 3
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 4
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subhs r0, r0, r2, ror #2 * 4
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 5
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subhs r0, r0, r2, ror #2 * 5
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 6
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subhs r0, r0, r2, ror #2 * 6
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 7
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subhs r0, r0, r2, ror #2 * 7
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 8
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subhs r0, r0, r2, ror #2 * 8
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 9
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subhs r0, r0, r2, ror #2 * 9
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 10
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subhs r0, r0, r2, ror #2 * 10
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 11
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subhs r0, r0, r2, ror #2 * 11
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 12
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subhs r0, r0, r2, ror #2 * 12
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 13
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subhs r0, r0, r2, ror #2 * 13
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 14
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subhs r0, r0, r2, ror #2 * 14
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adc r2, r1, r2, lsl #1
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cmp r0, r2, ror #2 * 15
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subhs r0, r0, r2, ror #2 * 15
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adc r2, r1, r2, lsl #1
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bic r0, r2, #3 << 30 @ for rounding add: cmp r0, r2 adc r2, #1
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bx lr
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.fnend
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