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[sil-code-motion] If we find an Inst that can not be proven to not alias a load, only invalidate that load instead of all of the loads.

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Swift SVN r13382
This commit is contained in:
Michael Gottesman
2014-02-03 23:05:03 +00:00
parent 4d544207e7
commit 1d1de86f37
1 changed files with 13 additions and 19 deletions
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32
lib/SILPasses/SILCodeMotion.cpp
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@@ -34,23 +34,11 @@ using namespace swift;
static const int SinkSearchWindow = 6;
/// Visit all loads we are tracking so far and return true if any of
/// them can potentially alias one of Inst's arguments. If they can
/// not, then Inst even though it writes memory can not affect the
/// values we are loading.
static bool mayAliasLoadSet(AliasAnalysis &AA, SILInstruction *Inst,
llvm::SmallVectorImpl<LoadInst *> &Loads) {
for (auto *LI : Loads)
if (AA.alias(Inst, SILValue(LI)) != AliasAnalysis::Result::NoAlias)
return true;
return false;
}
/// \brief Promote stored values to loads, remove dead stores and merge
/// duplicated loads.
void promoteMemoryOperationsInBlock(SILBasicBlock *BB, AliasAnalysis &AA) {
StoreInst *PrevStore = 0;
llvm::SmallVector<LoadInst *, 8> Loads;
llvm::SmallPtrSet<LoadInst *, 8> Loads;
auto II = BB->begin(), E = BB->end();
while (II != E) {
@@ -95,7 +83,7 @@ void promoteMemoryOperationsInBlock(SILBasicBlock *BB, AliasAnalysis &AA) {
}
if (LI)
Loads.push_back(LI);
Loads.insert(LI);
continue;
}
@@ -116,11 +104,17 @@ void promoteMemoryOperationsInBlock(SILBasicBlock *BB, AliasAnalysis &AA) {
if (Inst->mayReadFromMemory())
PrevStore = 0;
// If we have an instruction that may write to memory and we can
// not prove that it and its operands can not alias any of the
// loads we have visited so far, clear the loads.
if (Inst->mayWriteToMemory() && mayAliasLoadSet(AA, Inst, Loads))
Loads.clear();
// If we have an instruction that may write to memory and we can not prove
// that it and its operands can not alias a load we have visited, invalidate
// that load.
if (Inst->mayWriteToMemory()) {
llvm::SmallVector<LoadInst *, 4> InvalidatedLoadList;
for (auto *LI : Loads)
if (AA.alias(Inst, SILValue(LI)) != AliasAnalysis::Result::NoAlias)
InvalidatedLoadList.push_back(LI);
for (auto *LI : InvalidatedLoadList)
Loads.erase(LI);
}
}
}