bca568bfc5
Of course, functions called WebRtcSpl_AddSatW32 and WebRtcSpl_SubSatW32 are supposed to handle overflow gracefully, and they probably did. But since the overflow handling depended on undefined behavior, a sufficiently smart optimizing compiler would have realized that it could just ignore the possibility of overflow and omit all the overflow handling code, leaving only the unadorned addition or subtraction. Also, the new implementations, unlike the old ones, result in branch-free code (tested with clang 3.9 with -O2). BUG=chromium:601728 Review-Url: https://codereview.webrtc.org/2002523002 Cr-Commit-Position: refs/heads/master@{#12846}
164 lines
4.1 KiB
C
164 lines
4.1 KiB
C
/*
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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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// This header file includes the inline functions in
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// the fix point signal processing library.
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#ifndef WEBRTC_SPL_SPL_INL_H_
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#define WEBRTC_SPL_SPL_INL_H_
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#ifdef WEBRTC_ARCH_ARM_V7
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#include "webrtc/common_audio/signal_processing/include/spl_inl_armv7.h"
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#else
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#if defined(MIPS32_LE)
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#include "webrtc/common_audio/signal_processing/include/spl_inl_mips.h"
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#endif
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#if !defined(MIPS_DSP_R1_LE)
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static __inline int16_t WebRtcSpl_SatW32ToW16(int32_t value32) {
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int16_t out16 = (int16_t) value32;
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if (value32 > 32767)
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out16 = 32767;
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else if (value32 < -32768)
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out16 = -32768;
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return out16;
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}
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static __inline int32_t WebRtcSpl_AddSatW32(int32_t a, int32_t b) {
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// Do the addition in unsigned numbers, since signed overflow is undefined
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// behavior.
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const int32_t sum = (int32_t)((uint32_t)a + (uint32_t)b);
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// a + b can't overflow if a and b have different signs. If they have the
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// same sign, a + b also has the same sign iff it didn't overflow.
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if ((a < 0) == (b < 0) && (a < 0) != (sum < 0)) {
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// The direction of the overflow is obvious from the sign of a + b.
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return sum < 0 ? INT32_MAX : INT32_MIN;
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}
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return sum;
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}
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static __inline int32_t WebRtcSpl_SubSatW32(int32_t a, int32_t b) {
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// Do the subtraction in unsigned numbers, since signed overflow is undefined
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// behavior.
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const int32_t diff = (int32_t)((uint32_t)a - (uint32_t)b);
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// a - b can't overflow if a and b have the same sign. If they have different
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// signs, a - b has the same sign as a iff it didn't overflow.
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if ((a < 0) != (b < 0) && (a < 0) != (diff < 0)) {
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// The direction of the overflow is obvious from the sign of a - b.
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return diff < 0 ? INT32_MAX : INT32_MIN;
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}
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return diff;
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}
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static __inline int16_t WebRtcSpl_AddSatW16(int16_t a, int16_t b) {
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return WebRtcSpl_SatW32ToW16((int32_t) a + (int32_t) b);
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}
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static __inline int16_t WebRtcSpl_SubSatW16(int16_t var1, int16_t var2) {
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return WebRtcSpl_SatW32ToW16((int32_t) var1 - (int32_t) var2);
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}
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#endif // #if !defined(MIPS_DSP_R1_LE)
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#if !defined(MIPS32_LE)
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static __inline int16_t WebRtcSpl_GetSizeInBits(uint32_t n) {
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int16_t bits;
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if (0xFFFF0000 & n) {
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bits = 16;
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} else {
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bits = 0;
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}
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if (0x0000FF00 & (n >> bits)) bits += 8;
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if (0x000000F0 & (n >> bits)) bits += 4;
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if (0x0000000C & (n >> bits)) bits += 2;
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if (0x00000002 & (n >> bits)) bits += 1;
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if (0x00000001 & (n >> bits)) bits += 1;
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return bits;
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}
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static __inline int16_t WebRtcSpl_NormW32(int32_t a) {
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int16_t zeros;
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if (a == 0) {
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return 0;
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}
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else if (a < 0) {
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a = ~a;
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}
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if (!(0xFFFF8000 & a)) {
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zeros = 16;
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} else {
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zeros = 0;
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}
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if (!(0xFF800000 & (a << zeros))) zeros += 8;
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if (!(0xF8000000 & (a << zeros))) zeros += 4;
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if (!(0xE0000000 & (a << zeros))) zeros += 2;
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if (!(0xC0000000 & (a << zeros))) zeros += 1;
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return zeros;
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}
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static __inline int16_t WebRtcSpl_NormU32(uint32_t a) {
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int16_t zeros;
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if (a == 0) return 0;
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if (!(0xFFFF0000 & a)) {
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zeros = 16;
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} else {
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zeros = 0;
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}
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if (!(0xFF000000 & (a << zeros))) zeros += 8;
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if (!(0xF0000000 & (a << zeros))) zeros += 4;
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if (!(0xC0000000 & (a << zeros))) zeros += 2;
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if (!(0x80000000 & (a << zeros))) zeros += 1;
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return zeros;
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}
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static __inline int16_t WebRtcSpl_NormW16(int16_t a) {
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int16_t zeros;
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if (a == 0) {
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return 0;
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}
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else if (a < 0) {
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a = ~a;
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}
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if (!(0xFF80 & a)) {
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zeros = 8;
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} else {
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zeros = 0;
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}
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if (!(0xF800 & (a << zeros))) zeros += 4;
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if (!(0xE000 & (a << zeros))) zeros += 2;
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if (!(0xC000 & (a << zeros))) zeros += 1;
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return zeros;
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}
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static __inline int32_t WebRtc_MulAccumW16(int16_t a, int16_t b, int32_t c) {
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return (a * b + c);
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}
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#endif // #if !defined(MIPS32_LE)
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#endif // WEBRTC_ARCH_ARM_V7
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#endif // WEBRTC_SPL_SPL_INL_H_
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