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Finish making AliasAnalysis aware of the fact that most atomic intrinsics only dereference their arguments, and enhance

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BasicAA to make use of this fact when computing ModRef info.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63718 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2009-02-04 05:16:46 +00:00
parent 39355f9fea
commit fe9388ccb4
3 changed files with 51 additions and 0 deletions
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21
lib/Analysis/AliasAnalysis.cpp
View File

@ -150,6 +150,27 @@ AliasAnalysis::getModRefBehavior(CallSite CS,
AliasAnalysis::ModRefBehavior AliasAnalysis::ModRefBehavior
AliasAnalysis::getModRefBehavior(Function *F, AliasAnalysis::getModRefBehavior(Function *F,
std::vector<PointerAccessInfo> *Info) { std::vector<PointerAccessInfo> *Info) {
if (F->isIntrinsic()) {
switch (F->getIntrinsicID()) {
case Intrinsic::atomic_cmp_swap:
case Intrinsic::atomic_load_add:
case Intrinsic::atomic_load_and:
case Intrinsic::atomic_load_max:
case Intrinsic::atomic_load_min:
case Intrinsic::atomic_load_nand:
case Intrinsic::atomic_load_or:
case Intrinsic::atomic_load_sub:
case Intrinsic::atomic_load_umax:
case Intrinsic::atomic_load_umin:
case Intrinsic::atomic_load_xor:
case Intrinsic::atomic_swap:
// CAS and related intrinsics only access their arguments.
return AliasAnalysis::AccessesArguments;
default:
break;
}
}
if (F->doesNotAccessMemory()) if (F->doesNotAccessMemory())
// Can't do better than this. // Can't do better than this.
return DoesNotAccessMemory; return DoesNotAccessMemory;

16
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -256,6 +256,22 @@ bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
// //
AliasAnalysis::ModRefResult AliasAnalysis::ModRefResult
BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) { BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
// If the function only accesses its arguments, it suffices to check that
// P does not alias any of those arguments.
if (AliasAnalysis::getModRefBehavior(CS, 0) ==
AliasAnalysis::AccessesArguments) {
bool doesAlias = false;
for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
AI != AE; ++AI)
if (alias(*AI, ~0U, P, Size) != NoAlias) {
doesAlias = true;
break;
}
if (!doesAlias)
return NoModRef;
}
if (!isa<Constant>(P)) { if (!isa<Constant>(P)) {
const Value *Object = P->getUnderlyingObject(); const Value *Object = P->getUnderlyingObject();

14
test/Analysis/BasicAA/cas.ll Normal file
View File

@ -0,0 +1,14 @@
; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep load | count 1
@flag0 = internal global i32 zeroinitializer
@turn = internal global i32 zeroinitializer
define i32 @main() {
%a = load i32* @flag0
%b = tail call i32 @llvm.atomic.swap.i32.p0i32(i32* @turn, i32 1)
%c = load i32* @flag0
ret i32 %c
}
declare i32 @llvm.atomic.swap.i32.p0i32(i32*, i32) nounwind