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Add clz functions (Count number of Leading Zero bits), 32-and 64-bit variants

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Using __builtin_clz on gcc/clang, and a fallback implementation
otherwise.

Also redefine WebRtcSpl_GetSizeInBits(x) as simply 32 - clz32(x).

BUG=chromium:601787

Review-Url: https://codereview.webrtc.org/2014023002
Cr-Commit-Position: refs/heads/master@{#13014}
This commit is contained in:
kwiberg 2016-06-02 04:02:12 -07:00 committed by Commit bot
parent 116e4d4fae
commit 729b21f97f
7 changed files with 113 additions and 73 deletions
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1
webrtc/common_audio/BUILD.gn
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@ -81,6 +81,7 @@ source_set("common_audio") {
"signal_processing/resample_by_2_internal.h",
"signal_processing/resample_fractional.c",
"signal_processing/spl_init.c",
"signal_processing/spl_inl.c",
"signal_processing/spl_sqrt.c",
"signal_processing/splitting_filter.c",
"signal_processing/sqrt_of_one_minus_x_squared.c",

1
webrtc/common_audio/common_audio.gyp
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@ -94,6 +94,7 @@
'signal_processing/resample_by_2_internal.h',
'signal_processing/resample_fractional.c',
'signal_processing/spl_init.c',
'signal_processing/spl_inl.c',
'signal_processing/spl_sqrt.c',
'signal_processing/spl_sqrt_floor.c',
'signal_processing/splitting_filter.c',

2
webrtc/common_audio/real_fourier.cc
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@ -13,7 +13,7 @@
#include "webrtc/base/checks.h"
#include "webrtc/common_audio/real_fourier_ooura.h"
#include "webrtc/common_audio/real_fourier_openmax.h"
#include "webrtc/common_audio/signal_processing/include/spl_inl.h"
#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
namespace webrtc {

127
webrtc/common_audio/signal_processing/include/spl_inl.h
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@ -15,6 +15,54 @@
#ifndef WEBRTC_SPL_SPL_INL_H_
#define WEBRTC_SPL_SPL_INL_H_
#include "webrtc/system_wrappers/include/compile_assert_c.h"
extern const int8_t kWebRtcSpl_CountLeadingZeros32_Table[64];
// Don't call this directly except in tests!
static __inline int WebRtcSpl_CountLeadingZeros32_NotBuiltin(uint32_t n) {
// Normalize n by rounding up to the nearest number that is a sequence of 0
// bits followed by a sequence of 1 bits. This number has the same number of
// leading zeros as the original n. There are exactly 33 such values.
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
// Multiply the modified n with a constant selected (by exhaustive search)
// such that each of the 33 possible values of n give a product whose 6 most
// significant bits are unique. Then look up the answer in the table.
return kWebRtcSpl_CountLeadingZeros32_Table[(n * 0x8c0b2891) >> 26];
}
// Don't call this directly except in tests!
static __inline int WebRtcSpl_CountLeadingZeros64_NotBuiltin(uint64_t n) {
const int leading_zeros = n >> 32 == 0 ? 32 : 0;
return leading_zeros + WebRtcSpl_CountLeadingZeros32_NotBuiltin(
(uint32_t)(n >> (32 - leading_zeros)));
}
// Returns the number of leading zero bits in the argument.
static __inline int WebRtcSpl_CountLeadingZeros32(uint32_t n) {
#ifdef __GNUC__
COMPILE_ASSERT(sizeof(unsigned int) == sizeof(uint32_t));
return n == 0 ? 32 : __builtin_clz(n);
#else
return WebRtcSpl_CountLeadingZeros32_NotBuiltin(n);
#endif
}
// Returns the number of leading zero bits in the argument.
static __inline int WebRtcSpl_CountLeadingZeros64(uint64_t n) {
#ifdef __GNUC__
COMPILE_ASSERT(sizeof(unsigned long long) == sizeof(uint64_t));
return n == 0 ? 64 : __builtin_clzll(n);
#else
return WebRtcSpl_CountLeadingZeros64_NotBuiltin(n);
#endif
}
#ifdef WEBRTC_ARCH_ARM_V7
#include "webrtc/common_audio/signal_processing/include/spl_inl_armv7.h"
#else
@ -74,83 +122,26 @@ static __inline int16_t WebRtcSpl_SubSatW16(int16_t var1, int16_t var2) {
#if !defined(MIPS32_LE)
static __inline int16_t WebRtcSpl_GetSizeInBits(uint32_t n) {
int16_t bits;
if (0xFFFF0000 & n) {
bits = 16;
} else {
bits = 0;
}
if (0x0000FF00 & (n >> bits)) bits += 8;
if (0x000000F0 & (n >> bits)) bits += 4;
if (0x0000000C & (n >> bits)) bits += 2;
if (0x00000002 & (n >> bits)) bits += 1;
if (0x00000001 & (n >> bits)) bits += 1;
return bits;
return 32 - WebRtcSpl_CountLeadingZeros32(n);
}
// Return the number of steps a can be left-shifted without overflow,
// or 0 if a == 0.
static __inline int16_t WebRtcSpl_NormW32(int32_t a) {
int16_t zeros;
if (a == 0) {
return 0;
}
else if (a < 0) {
a = ~a;
}
if (!(0xFFFF8000 & a)) {
zeros = 16;
} else {
zeros = 0;
}
if (!(0xFF800000 & (a << zeros))) zeros += 8;
if (!(0xF8000000 & (a << zeros))) zeros += 4;
if (!(0xE0000000 & (a << zeros))) zeros += 2;
if (!(0xC0000000 & (a << zeros))) zeros += 1;
return zeros;
return a == 0 ? 0 : WebRtcSpl_CountLeadingZeros32(a < 0 ? ~a : a) - 1;
}
// Return the number of steps a can be left-shifted without overflow,
// or 0 if a == 0.
static __inline int16_t WebRtcSpl_NormU32(uint32_t a) {
int16_t zeros;
if (a == 0) return 0;
if (!(0xFFFF0000 & a)) {
zeros = 16;
} else {
zeros = 0;
}
if (!(0xFF000000 & (a << zeros))) zeros += 8;
if (!(0xF0000000 & (a << zeros))) zeros += 4;
if (!(0xC0000000 & (a << zeros))) zeros += 2;
if (!(0x80000000 & (a << zeros))) zeros += 1;
return zeros;
return a == 0 ? 0 : WebRtcSpl_CountLeadingZeros32(a);
}
// Return the number of steps a can be left-shifted without overflow,
// or 0 if a == 0.
static __inline int16_t WebRtcSpl_NormW16(int16_t a) {
int16_t zeros;
if (a == 0) {
return 0;
}
else if (a < 0) {
a = ~a;
}
if (!(0xFF80 & a)) {
zeros = 8;
} else {
zeros = 0;
}
if (!(0xF800 & (a << zeros))) zeros += 4;
if (!(0xE000 & (a << zeros))) zeros += 2;
if (!(0xC000 & (a << zeros))) zeros += 1;
return zeros;
const int32_t a32 = a;
return a == 0 ? 0 : WebRtcSpl_CountLeadingZeros32(a < 0 ? ~a32 : a32) - 17;
}
static __inline int32_t WebRtc_MulAccumW16(int16_t a, int16_t b, int32_t c) {

26
webrtc/common_audio/signal_processing/signal_processing_unittest.cc
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@ -142,6 +142,32 @@ TEST_F(SplTest, AddSubSatW32) {
}
}
TEST_F(SplTest, CountLeadingZeros32) {
EXPECT_EQ(32, WebRtcSpl_CountLeadingZeros32(0));
EXPECT_EQ(32, WebRtcSpl_CountLeadingZeros32_NotBuiltin(0));
for (int i = 0; i < 32; ++i) {
const uint32_t single_one = uint32_t{1} << i;
const uint32_t all_ones = 2 * single_one - 1;
EXPECT_EQ(31 - i, WebRtcSpl_CountLeadingZeros32(single_one));
EXPECT_EQ(31 - i, WebRtcSpl_CountLeadingZeros32_NotBuiltin(single_one));
EXPECT_EQ(31 - i, WebRtcSpl_CountLeadingZeros32(all_ones));
EXPECT_EQ(31 - i, WebRtcSpl_CountLeadingZeros32_NotBuiltin(all_ones));
}
}
TEST_F(SplTest, CountLeadingZeros64) {
EXPECT_EQ(64, WebRtcSpl_CountLeadingZeros64(0));
EXPECT_EQ(64, WebRtcSpl_CountLeadingZeros64_NotBuiltin(0));
for (int i = 0; i < 64; ++i) {
const uint64_t single_one = uint64_t{1} << i;
const uint64_t all_ones = 2 * single_one - 1;
EXPECT_EQ(63 - i, WebRtcSpl_CountLeadingZeros64(single_one));
EXPECT_EQ(63 - i, WebRtcSpl_CountLeadingZeros64_NotBuiltin(single_one));
EXPECT_EQ(63 - i, WebRtcSpl_CountLeadingZeros64(all_ones));
EXPECT_EQ(63 - i, WebRtcSpl_CountLeadingZeros64_NotBuiltin(all_ones));
}
}
TEST_F(SplTest, MathOperationsTest) {
int A = 1134567892;
int32_t num = 117;

24
webrtc/common_audio/signal_processing/spl_inl.c Normal file
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@ -0,0 +1,24 @@
/*
* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <stdint.h>
#include "webrtc/common_audio/signal_processing/include/spl_inl.h"
// Table used by WebRtcSpl_CountLeadingZeros32_NotBuiltin. For each uint32_t n
// that's a sequence of 0 bits followed by a sequence of 1 bits, the entry at
// index (n * 0x8c0b2891) >> 26 in this table gives the number of zero bits in
// n.
const int8_t kWebRtcSpl_CountLeadingZeros32_Table[64] = {
32, 8, 17, -1, -1, 14, -1, -1, -1, 20, -1, -1, -1, 28, -1, 18,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 26, 25, 24,
4, 11, 23, 31, 3, 7, 10, 16, 22, 30, -1, -1, 2, 6, 13, 9,
-1, 15, -1, 21, -1, 29, 19, -1, -1, -1, -1, -1, 1, 27, 5, 12,
};

5
webrtc/system_wrappers/include/compile_assert_c.h
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@ -11,14 +11,11 @@
#ifndef WEBRTC_SYSTEM_WRAPPERS_INCLUDE_COMPILE_ASSERT_H_
#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_COMPILE_ASSERT_H_
#ifdef __cplusplus
#error "Only use this for C files. For C++, use static_assert."
#endif
// Use this macro to verify at compile time that certain restrictions are met.
// The argument is the boolean expression to evaluate.
// Example:
// COMPILE_ASSERT(sizeof(foo) < 128);
// Note: In C++, use static_assert instead!
#define COMPILE_ASSERT(expression) switch (0) {case 0: case expression:;}
#endif // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_COMPILE_ASSERT_H_