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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /js/src/jit/shared/AtomicOperations-shared-jit.cpp | |
parent | Initial commit. (diff) | |
download | thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.tar.xz thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | js/src/jit/shared/AtomicOperations-shared-jit.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/js/src/jit/shared/AtomicOperations-shared-jit.cpp b/js/src/jit/shared/AtomicOperations-shared-jit.cpp new file mode 100644 index 0000000000..df7c049dfa --- /dev/null +++ b/js/src/jit/shared/AtomicOperations-shared-jit.cpp @@ -0,0 +1,180 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=4 et sw=4 tw=99: + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "jit/AtomicOperations.h" + +#if defined(__arm__) +# include "jit/arm/Architecture-arm.h" +#endif + +#ifdef JS_HAVE_GENERATED_ATOMIC_OPS + +# include <atomic> + +# include "js/GCAPI.h" + +using namespace js; +using namespace js::jit; + +// A "block" is a sequence of bytes that is a reasonable quantum to copy to +// amortize call overhead when implementing memcpy and memmove. A block will +// not fit in registers on all platforms and copying it without using +// intermediate memory will therefore be sensitive to overlap. +// +// A "word" is an item that we can copy using only register intermediate storage +// on all platforms; words can be individually copied without worrying about +// overlap. +// +// Blocks and words can be aligned or unaligned; specific (generated) copying +// functions handle this in platform-specific ways. + +static constexpr size_t WORDSIZE = sizeof(uintptr_t); +static constexpr size_t BLOCKSIZE = 8 * WORDSIZE; // Must be a power of 2 + +static_assert(BLOCKSIZE % WORDSIZE == 0, + "A block is an integral number of words"); + +// Constants must match the ones in GenerateAtomicOperations.py +static_assert(JS_GENERATED_ATOMICS_BLOCKSIZE == BLOCKSIZE); +static_assert(JS_GENERATED_ATOMICS_WORDSIZE == WORDSIZE); + +static constexpr size_t WORDMASK = WORDSIZE - 1; +static constexpr size_t BLOCKMASK = BLOCKSIZE - 1; + +namespace js { +namespace jit { + +static bool UnalignedAccessesAreOK() { +# ifdef DEBUG + const char* flag = getenv("JS_NO_UNALIGNED_MEMCPY"); + if (flag && *flag == '1') return false; +# endif +# if defined(__x86_64__) || defined(__i386__) + return true; +# elif defined(__arm__) + return !HasAlignmentFault(); +# elif defined(__aarch64__) + // This is not necessarily true but it's the best guess right now. + return true; +# else +# error "Unsupported platform" +# endif +} + +# ifndef JS_64BIT +void AtomicCompilerFence() { + std::atomic_signal_fence(std::memory_order_acq_rel); +} +# endif + +void AtomicMemcpyDownUnsynchronized(uint8_t* dest, const uint8_t* src, + size_t nbytes) { + JS::AutoSuppressGCAnalysis nogc; + + const uint8_t* lim = src + nbytes; + + // Set up bulk copying. The cases are ordered the way they are on the + // assumption that if we can achieve aligned copies even with a little + // preprocessing then that is better than unaligned copying on a platform + // that supports it. + + if (nbytes >= WORDSIZE) { + void (*copyBlock)(uint8_t* dest, const uint8_t* src); + void (*copyWord)(uint8_t* dest, const uint8_t* src); + + if (((uintptr_t(dest) ^ uintptr_t(src)) & WORDMASK) == 0) { + const uint8_t* cutoff = (const uint8_t*)RoundUp(uintptr_t(src), WORDSIZE); + MOZ_ASSERT(cutoff <= lim); // because nbytes >= WORDSIZE + while (src < cutoff) { + AtomicCopyByteUnsynchronized(dest++, src++); + } + copyBlock = AtomicCopyBlockDownUnsynchronized; + copyWord = AtomicCopyWordUnsynchronized; + } else if (UnalignedAccessesAreOK()) { + copyBlock = AtomicCopyBlockDownUnsynchronized; + copyWord = AtomicCopyWordUnsynchronized; + } else { + copyBlock = AtomicCopyUnalignedBlockDownUnsynchronized; + copyWord = AtomicCopyUnalignedWordDownUnsynchronized; + } + + // Bulk copy, first larger blocks and then individual words. + + const uint8_t* blocklim = src + ((lim - src) & ~BLOCKMASK); + while (src < blocklim) { + copyBlock(dest, src); + dest += BLOCKSIZE; + src += BLOCKSIZE; + } + + const uint8_t* wordlim = src + ((lim - src) & ~WORDMASK); + while (src < wordlim) { + copyWord(dest, src); + dest += WORDSIZE; + src += WORDSIZE; + } + } + + // Byte copy any remaining tail. + + while (src < lim) { + AtomicCopyByteUnsynchronized(dest++, src++); + } +} + +void AtomicMemcpyUpUnsynchronized(uint8_t* dest, const uint8_t* src, + size_t nbytes) { + JS::AutoSuppressGCAnalysis nogc; + + const uint8_t* lim = src; + + src += nbytes; + dest += nbytes; + + if (nbytes >= WORDSIZE) { + void (*copyBlock)(uint8_t* dest, const uint8_t* src); + void (*copyWord)(uint8_t* dest, const uint8_t* src); + + if (((uintptr_t(dest) ^ uintptr_t(src)) & WORDMASK) == 0) { + const uint8_t* cutoff = (const uint8_t*)(uintptr_t(src) & ~WORDMASK); + MOZ_ASSERT(cutoff >= lim); // Because nbytes >= WORDSIZE + while (src > cutoff) { + AtomicCopyByteUnsynchronized(--dest, --src); + } + copyBlock = AtomicCopyBlockUpUnsynchronized; + copyWord = AtomicCopyWordUnsynchronized; + } else if (UnalignedAccessesAreOK()) { + copyBlock = AtomicCopyBlockUpUnsynchronized; + copyWord = AtomicCopyWordUnsynchronized; + } else { + copyBlock = AtomicCopyUnalignedBlockUpUnsynchronized; + copyWord = AtomicCopyUnalignedWordUpUnsynchronized; + } + + const uint8_t* blocklim = src - ((src - lim) & ~BLOCKMASK); + while (src > blocklim) { + dest -= BLOCKSIZE; + src -= BLOCKSIZE; + copyBlock(dest, src); + } + + const uint8_t* wordlim = src - ((src - lim) & ~WORDMASK); + while (src > wordlim) { + dest -= WORDSIZE; + src -= WORDSIZE; + copyWord(dest, src); + } + } + + while (src > lim) { + AtomicCopyByteUnsynchronized(--dest, --src); + } +} + +} // namespace jit +} // namespace js + +#endif // JS_HAVE_GENERATED_ATOMIC_OPS |