76 lines
2.6 KiB
C++
76 lines
2.6 KiB
C++
//===-- tsan_update_shadow_word_inl.h ---------------------------*- C++ -*-===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of ThreadSanitizer (TSan), a race detector.
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//
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// Body of the hottest inner loop.
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// If we wrap this body into a function, compilers (both gcc and clang)
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// produce sligtly less efficient code.
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//===----------------------------------------------------------------------===//
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do {
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StatInc(thr, StatShadowProcessed);
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const unsigned kAccessSize = 1 << kAccessSizeLog;
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unsigned off = cur.ComputeSearchOffset();
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u64 *sp = &shadow_mem[(idx + off) % kShadowCnt];
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old = LoadShadow(sp);
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if (old.IsZero()) {
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StatInc(thr, StatShadowZero);
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if (store_word)
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StoreIfNotYetStored(sp, &store_word);
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// The above StoreIfNotYetStored could be done unconditionally
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// and it even shows 4% gain on synthetic benchmarks (r4307).
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break;
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}
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// is the memory access equal to the previous?
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if (Shadow::Addr0AndSizeAreEqual(cur, old)) {
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StatInc(thr, StatShadowSameSize);
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// same thread?
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if (Shadow::TidsAreEqual(old, cur)) {
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StatInc(thr, StatShadowSameThread);
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if (OldIsInSameSynchEpoch(old, thr)) {
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if (old.IsRWNotWeaker(kAccessIsWrite, kIsAtomic)) {
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// found a slot that holds effectively the same info
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// (that is, same tid, same sync epoch and same size)
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StatInc(thr, StatMopSame);
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return;
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}
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StoreIfNotYetStored(sp, &store_word);
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break;
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}
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if (old.IsRWWeakerOrEqual(kAccessIsWrite, kIsAtomic))
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StoreIfNotYetStored(sp, &store_word);
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break;
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}
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StatInc(thr, StatShadowAnotherThread);
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if (HappensBefore(old, thr)) {
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StoreIfNotYetStored(sp, &store_word);
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break;
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}
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if (old.IsBothReadsOrAtomic(kAccessIsWrite, kIsAtomic))
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break;
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goto RACE;
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}
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// Do the memory access intersect?
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// In Go all memory accesses are 1 byte, so there can be no intersections.
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if (kCppMode && Shadow::TwoRangesIntersect(old, cur, kAccessSize)) {
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StatInc(thr, StatShadowIntersect);
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if (Shadow::TidsAreEqual(old, cur)) {
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StatInc(thr, StatShadowSameThread);
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break;
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}
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StatInc(thr, StatShadowAnotherThread);
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if (old.IsBothReadsOrAtomic(kAccessIsWrite, kIsAtomic))
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break;
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if (HappensBefore(old, thr))
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break;
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goto RACE;
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}
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// The accesses do not intersect.
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StatInc(thr, StatShadowNotIntersect);
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break;
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} while (0);
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