From e5e77281ca516b7b802eb6c9b4bc3b39e2a8201e Mon Sep 17 00:00:00 2001 From: Alon Zakai Date: Fri, 18 Aug 2017 13:58:14 -0700 Subject: Don't reorder an implicit trap with a global side effect (#1133) --- src/ast/effects.h | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'src') diff --git a/src/ast/effects.h b/src/ast/effects.h index 5392c0e50..2db671b5e 100644 --- a/src/ast/effects.h +++ b/src/ast/effects.h @@ -48,18 +48,18 @@ struct EffectAnalyzer : public PostWalker { bool readsMemory = false; bool writesMemory = false; bool implicitTrap = false; // a load or div/rem, which may trap. we ignore trap - // differences, so it is ok to reorder these, and we - // also allow reordering them with other effects - // (so a trap may occur later or earlier, if it is - // going to occur anyhow), but we can't remove them, - // they count as side effects + // differences, so it is ok to reorder these, but we can't + // remove them, as they count as side effects, and we + // can't move them in a way that would cause other noticeable + // (global) side effects bool isAtomic = false; // An atomic load/store/RMW/Cmpxchg or an operator that // has a defined ordering wrt atomics (e.g. grow_memory) bool accessesLocal() { return localsRead.size() + localsWritten.size() > 0; } bool accessesGlobal() { return globalsRead.size() + globalsWritten.size() > 0; } bool accessesMemory() { return calls || readsMemory || writesMemory; } - bool hasSideEffects() { return calls || localsWritten.size() > 0 || writesMemory || branches || globalsWritten.size() > 0 || implicitTrap || isAtomic; } + bool hasGlobalSideEffects() { return calls || globalsWritten.size() > 0 || writesMemory || isAtomic; } + bool hasSideEffects() { return hasGlobalSideEffects() || localsWritten.size() > 0 || branches || implicitTrap; } bool hasAnything() { return branches || calls || accessesLocal() || readsMemory || writesMemory || accessesGlobal() || implicitTrap || isAtomic; } // checks if these effects would invalidate another set (e.g., if we write, we invalidate someone that reads, they can't be moved past us) @@ -98,6 +98,10 @@ struct EffectAnalyzer : public PostWalker { if ((implicitTrap && other.branches) || (other.implicitTrap && branches)) { return true; } + // we can't reorder an implicit trap in a way that alters global state + if ((implicitTrap && other.hasGlobalSideEffects()) || (other.implicitTrap && hasGlobalSideEffects())) { + return true; + } return false; } -- cgit v1.2.3