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[sil-aa] Teach AA::getMemoryBehavior about a bunch more instructions which do

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not have their normal memory behavior if the value we are trying to find memory
behavior relative to does not alias their arguments.

Also cond_fail is inert from an AA perspective.

Swift SVN r16806
This commit is contained in:
Michael Gottesman
2014-04-25 06:37:01 +00:00
parent e604952ca9
commit a75de1c9a5
1 changed files with 41 additions and 18 deletions
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59
lib/SILAnalysis/AliasAnalysis.cpp
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@@ -443,13 +443,16 @@ namespace {
using MemBehavior = SILInstruction::MemoryBehavior;
/// Visitor that determines the memory behavior of an instruction relative to a
/// specific SILValue (i.e. can the instruction cause the value to be read,
/// etc.).
class MemoryBehaviorVisitor
: public SILInstructionVisitor<MemoryBehaviorVisitor, MemBehavior> {
// The alias analysis for any queries we may need.
/// The alias analysis for any queries we may need.
AliasAnalysis &AA;
// The value we are attempting to discover memory behavior relative to.
/// The value we are attempting to discover memory behavior relative to.
SILValue V;
public:
@@ -465,28 +468,48 @@ public:
return Inst->getMemoryBehavior();
}
MemBehavior visitLoadInst(LoadInst *LI);
MemBehavior visitStoreInst(StoreInst *SI);
MemBehavior visitApplyInst(ApplyInst *AI);
// Instructions which are none if our SILValue does not alias one of its
// arguments. If we can not prove such a thing, return the relevant memory
// behavior.
#define OPERANDALIAS_MEMBEHAVIOR_INST(Name) \
MemBehavior visit##Name(Name *I) { \
for (Operand &Op : I->getAllOperands()) { \
if (!AA.isNoAlias(Op.get(), V)) { \
DEBUG(llvm::dbgs() << " " #Name \
" does alias inst. Returning Normal behavior.\n"); \
return I->getMemoryBehavior(); \
} \
} \
\
DEBUG(llvm::dbgs() << " " #Name " does not alias inst. Returning " \
"None.\n"); \
return MemBehavior::None; \
}
OPERANDALIAS_MEMBEHAVIOR_INST(LoadInst)
OPERANDALIAS_MEMBEHAVIOR_INST(InjectEnumAddrInst)
OPERANDALIAS_MEMBEHAVIOR_INST(UncheckedTakeEnumDataAddrInst)
OPERANDALIAS_MEMBEHAVIOR_INST(InitExistentialInst)
OPERANDALIAS_MEMBEHAVIOR_INST(UpcastExistentialInst)
OPERANDALIAS_MEMBEHAVIOR_INST(DeinitExistentialInst)
OPERANDALIAS_MEMBEHAVIOR_INST(DeallocStackInst)
OPERANDALIAS_MEMBEHAVIOR_INST(FixLifetimeInst)
#undef OPERANDALIAS_MEMBEHAVIOR_INST
// Override simple behaviors where MayHaveSideEffects is too general and
// encompasses other behavior that is not read/write/ref count decrement
// behavior we care about.
#define SIMPLE_MEMBEHAVIOR_INST(Name, Behavior) \
MemBehavior visit##Name(Name *I) { return MemBehavior::Behavior; }
SIMPLE_MEMBEHAVIOR_INST(CondFailInst, None)
#undef SIMPLE_MEMBEHAVIOR_INST
};
} // end anonymous namespace
MemBehavior MemoryBehaviorVisitor::visitLoadInst(LoadInst *LI) {
// If the load address doesn't alias the given address, it doesn't read or
// write the specified memory.
if (AA.isNoAlias(LI->getOperand(), V)) {
DEBUG(llvm::dbgs() << " Load does not alias inst. Returning None.\n");
return MemBehavior::None;
}
// Otherwise be conservative and just return reads since loads can only
// read.
DEBUG(llvm::dbgs() << " Could not prove load does not alias inst. "
"Returning MayRead.\n");
return MemBehavior::MayRead;
}
MemBehavior MemoryBehaviorVisitor::visitStoreInst(StoreInst *SI) {
// If the store dest cannot alias the pointer in question, then the
// specified value can not be modified by the store.