f7927dd607
git-svn-id: http://skia.googlecode.com/svn/trunk@14270 2bbb7eff-a529-9590-31e7-b0007b416f81
230 lines
6.5 KiB
C++
230 lines
6.5 KiB
C++
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/*
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* Copyright 2006 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkMath_DEFINED
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#define SkMath_DEFINED
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#include "SkTypes.h"
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// 64bit -> 32bit utilities
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/**
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* Return true iff the 64bit value can exactly be represented in signed 32bits
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*/
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static inline bool sk_64_isS32(int64_t value) {
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return (int32_t)value == value;
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}
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/**
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* Return the 64bit argument as signed 32bits, asserting in debug that the arg
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* exactly fits in signed 32bits. In the release build, no checks are preformed
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* and the return value if the arg does not fit is undefined.
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*/
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static inline int32_t sk_64_asS32(int64_t value) {
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SkASSERT(sk_64_isS32(value));
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return (int32_t)value;
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}
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// Handy util that can be passed two ints, and will automatically promote to
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// 64bits before the multiply, so the caller doesn't have to remember to cast
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// e.g. (int64_t)a * b;
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static inline int64_t sk_64_mul(int64_t a, int64_t b) {
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return a * b;
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}
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///////////////////////////////////////////////////////////////////////////////
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/**
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* Computes numer1 * numer2 / denom in full 64 intermediate precision.
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* It is an error for denom to be 0. There is no special handling if
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* the result overflows 32bits.
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*/
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static inline int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom) {
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SkASSERT(denom);
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int64_t tmp = sk_64_mul(numer1, numer2) / denom;
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return sk_64_asS32(tmp);
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}
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/**
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* Computes (numer1 << shift) / denom in full 64 intermediate precision.
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* It is an error for denom to be 0. There is no special handling if
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* the result overflows 32bits.
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*/
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int32_t SkDivBits(int32_t numer, int32_t denom, int shift);
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/**
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* Return the integer square root of value, with a bias of bitBias
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*/
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int32_t SkSqrtBits(int32_t value, int bitBias);
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/** Return the integer square root of n, treated as a SkFixed (16.16)
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*/
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#define SkSqrt32(n) SkSqrtBits(n, 15)
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//! Returns the number of leading zero bits (0...32)
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int SkCLZ_portable(uint32_t);
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#ifndef SkCLZ
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#if defined(_MSC_VER) && _MSC_VER >= 1400
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#include <intrin.h>
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static inline int SkCLZ(uint32_t mask) {
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if (mask) {
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DWORD index;
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_BitScanReverse(&index, mask);
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return index ^ 0x1F;
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} else {
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return 32;
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}
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}
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#elif defined(SK_CPU_ARM) || defined(__GNUC__) || defined(__clang__)
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static inline int SkCLZ(uint32_t mask) {
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// __builtin_clz(0) is undefined, so we have to detect that case.
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return mask ? __builtin_clz(mask) : 32;
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}
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#else
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#define SkCLZ(x) SkCLZ_portable(x)
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#endif
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#endif
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/**
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* Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
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*/
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static inline int SkClampPos(int value) {
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return value & ~(value >> 31);
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}
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/** Given an integer and a positive (max) integer, return the value
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* pinned against 0 and max, inclusive.
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* @param value The value we want returned pinned between [0...max]
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* @param max The positive max value
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* @return 0 if value < 0, max if value > max, else value
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*/
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static inline int SkClampMax(int value, int max) {
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// ensure that max is positive
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SkASSERT(max >= 0);
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if (value < 0) {
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value = 0;
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}
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if (value > max) {
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value = max;
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}
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return value;
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}
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/**
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* Returns the smallest power-of-2 that is >= the specified value. If value
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* is already a power of 2, then it is returned unchanged. It is undefined
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* if value is <= 0.
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*/
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static inline int SkNextPow2(int value) {
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SkASSERT(value > 0);
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return 1 << (32 - SkCLZ(value - 1));
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}
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/**
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* Returns the log2 of the specified value, were that value to be rounded up
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* to the next power of 2. It is undefined to pass 0. Examples:
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* SkNextLog2(1) -> 0
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* SkNextLog2(2) -> 1
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* SkNextLog2(3) -> 2
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* SkNextLog2(4) -> 2
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* SkNextLog2(5) -> 3
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*/
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static inline int SkNextLog2(uint32_t value) {
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SkASSERT(value != 0);
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return 32 - SkCLZ(value - 1);
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}
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/**
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* Returns true if value is a power of 2. Does not explicitly check for
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* value <= 0.
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*/
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static inline bool SkIsPow2(int value) {
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return (value & (value - 1)) == 0;
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}
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///////////////////////////////////////////////////////////////////////////////
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/**
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* SkMulS16(a, b) multiplies a * b, but requires that a and b are both int16_t.
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* With this requirement, we can generate faster instructions on some
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* architectures.
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*/
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#ifdef SK_ARM_HAS_EDSP
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static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
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SkASSERT((int16_t)x == x);
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SkASSERT((int16_t)y == y);
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int32_t product;
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asm("smulbb %0, %1, %2 \n"
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: "=r"(product)
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: "r"(x), "r"(y)
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);
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return product;
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}
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#else
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#ifdef SK_DEBUG
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static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
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SkASSERT((int16_t)x == x);
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SkASSERT((int16_t)y == y);
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return x * y;
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}
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#else
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#define SkMulS16(x, y) ((x) * (y))
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#endif
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#endif
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/**
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* Return a*b/((1 << shift) - 1), rounding any fractional bits.
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* Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
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*/
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static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
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SkASSERT(a <= 32767);
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SkASSERT(b <= 32767);
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SkASSERT(shift > 0 && shift <= 8);
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unsigned prod = SkMulS16(a, b) + (1 << (shift - 1));
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return (prod + (prod >> shift)) >> shift;
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}
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/**
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* Return a*b/255, rounding any fractional bits.
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* Only valid if a and b are unsigned and <= 32767.
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*/
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static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
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SkASSERT(a <= 32767);
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SkASSERT(b <= 32767);
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unsigned prod = SkMulS16(a, b) + 128;
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return (prod + (prod >> 8)) >> 8;
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}
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/**
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* Stores numer/denom and numer%denom into div and mod respectively.
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*/
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template <typename In, typename Out>
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inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
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#ifdef SK_CPU_ARM
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// If we wrote this as in the else branch, GCC won't fuse the two into one
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// divmod call, but rather a div call followed by a divmod. Silly! This
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// version is just as fast as calling __aeabi_[u]idivmod manually, but with
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// prettier code.
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//
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// This benches as around 2x faster than the code in the else branch.
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const In d = numer/denom;
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*div = static_cast<Out>(d);
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*mod = static_cast<Out>(numer-d*denom);
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#else
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// On x86 this will just be a single idiv.
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*div = static_cast<Out>(numer/denom);
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*mod = static_cast<Out>(numer%denom);
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#endif // SK_CPU_ARM
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}
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#endif
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