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[sanitizer] Correct 64-bit atomic_store on 32-bit "other" platforms
Summary: I think there might be something to optimize in `atomic_store`. Currently, if everything goes well (and we have a different new value), we always iterate 3 times. For example, `with a = 0`, `oldval = a`, `newval = 42`, we get: ``` oldval = 0, newval = 42, curval = 0 oldval = 0, newval = 42, curval = 42 oldval = 42, newval = 42, curval = 42 ``` and then it breaks. Unless I am not seeing something, I don't see a point to the third iteration. If the current value is the one we want, we should just break. This means that 2 iterations (with a different newval) should be sufficient to achieve what we want. Reviewers: dvyukov, alekseyshl Reviewed By: dvyukov Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits Differential Revision: https://reviews.llvm.org/D46597 llvm-svn: 331890
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@ -86,7 +86,7 @@ INLINE void atomic_store(volatile T *a, typename T::Type v, memory_order mo) {
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typename T::Type cur;
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for (;;) {
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cur = __sync_val_compare_and_swap(&a->val_dont_use, cmp, v);
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if (cmp == v)
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if (cur == cmp || cur == v)
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break;
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cmp = cur;
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}
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