Add an Intraprocedural form of BasicAliasAnalysis, which aims to
properly handles instructions and arguments defined in different
functions, or across recursive function iterations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107109 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 1bf32ce..c2ae32f 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -55,9 +55,10 @@
/// isNonEscapingLocalObject - Return true if the pointer is to a function-local
/// object that never escapes from the function.
-static bool isNonEscapingLocalObject(const Value *V) {
+static bool isNonEscapingLocalObject(const Value *V, bool Interprocedural) {
// If this is a local allocation, check to see if it escapes.
- if (isa<AllocaInst>(V) || isNoAliasCall(V))
+ if (isa<AllocaInst>(V) ||
+ (!Interprocedural && isNoAliasCall(V)))
// Set StoreCaptures to True so that we can assume in our callers that the
// pointer is not the result of a load instruction. Currently
// PointerMayBeCaptured doesn't have any special analysis for the
@@ -68,16 +69,32 @@
// If this is an argument that corresponds to a byval or noalias argument,
// then it has not escaped before entering the function. Check if it escapes
// inside the function.
- if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr() || A->hasNoAliasAttr()) {
- // Don't bother analyzing arguments already known not to escape.
- if (A->hasNoCaptureAttr())
- return true;
- return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
- }
+ if (!Interprocedural)
+ if (const Argument *A = dyn_cast<Argument>(V))
+ if (A->hasByValAttr() || A->hasNoAliasAttr()) {
+ // Don't bother analyzing arguments already known not to escape.
+ if (A->hasNoCaptureAttr())
+ return true;
+ return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
+ }
return false;
}
+/// isEscapeSource - Return true if the pointer is one which would have
+/// been considered an escape by isNonEscapingLocalObject.
+static bool isEscapeSource(const Value *V, bool Interprocedural) {
+ if (!Interprocedural)
+ if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
+ return true;
+
+ // The load case works because isNonEscapingLocalObject considers all
+ // stores to be escapes (it passes true for the StoreCaptures argument
+ // to PointerMayBeCaptured).
+ if (isa<LoadInst>(V))
+ return true;
+
+ return false;
+}
/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
@@ -177,19 +194,51 @@
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
//===----------------------------------------------------------------------===//
-// BasicAA Pass
+// BasicAliasAnalysis Pass
//===----------------------------------------------------------------------===//
+static const Function *getParent(const Value *V) {
+ if(const Instruction *inst = dyn_cast<Instruction>(V))
+ return inst->getParent()->getParent();
+
+ if(const Argument *arg = dyn_cast<Argument>(V))
+ return arg->getParent();
+
+ return NULL;
+}
+
+static bool sameParent(const Value *O1, const Value *O2) {
+
+ const Function *F1 = getParent(O1);
+ const Function *F2 = getParent(O2);
+
+ return !F1 || !F2 || F1 == F2;
+}
+
namespace {
/// BasicAliasAnalysis - This is the default alias analysis implementation.
/// Because it doesn't chain to a previous alias analysis (like -no-aa), it
/// derives from the NoAA class.
struct BasicAliasAnalysis : public NoAA {
+ /// Interprocedural - Flag for "interprocedural" mode, where we must
+ /// support queries of values which live in different functions.
+ bool Interprocedural;
+
static char ID; // Class identification, replacement for typeinfo
- BasicAliasAnalysis() : NoAA(&ID) {}
+ BasicAliasAnalysis()
+ : NoAA(&ID), Interprocedural(false) {}
+ BasicAliasAnalysis(void *PID, bool interprocedural)
+ : NoAA(PID), Interprocedural(interprocedural) {}
+
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
assert(Visited.empty() && "Visited must be cleared after use!");
+#ifdef XDEBUG
+ assert((Interprocedural || sameParent(V1, V2)) &&
+ "BasicAliasAnalysis (-basicaa) doesn't support interprocedural "
+ "queries; use InterproceduralAliasAnalysis "
+ "(-interprocedural-basic-aa) instead.");
+#endif
AliasResult Alias = aliasCheck(V1, V1Size, V2, V2Size);
Visited.clear();
return Alias;
@@ -284,7 +333,7 @@
// then the call can not mod/ref the pointer unless the call takes the pointer
// as an argument, and itself doesn't capture it.
if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
- isNonEscapingLocalObject(Object)) {
+ isNonEscapingLocalObject(Object, Interprocedural)) {
bool PassedAsArg = false;
unsigned ArgNo = 0;
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
@@ -705,18 +754,25 @@
if (O1 != O2) {
// If V1/V2 point to two different objects we know that we have no alias.
- if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
+ if (isIdentifiedObject(O1, Interprocedural) &&
+ isIdentifiedObject(O2, Interprocedural))
return NoAlias;
// Constant pointers can't alias with non-const isIdentifiedObject objects.
- if ((isa<Constant>(O1) && isIdentifiedObject(O2) && !isa<Constant>(O2)) ||
- (isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
+ if ((isa<Constant>(O1) &&
+ isIdentifiedObject(O2, Interprocedural) &&
+ !isa<Constant>(O2)) ||
+ (isa<Constant>(O2) &&
+ isIdentifiedObject(O1, Interprocedural) &&
+ !isa<Constant>(O1)))
return NoAlias;
- // Arguments can't alias with local allocations or noalias calls.
- if ((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1))))
- return NoAlias;
+ // Arguments can't alias with local allocations or noalias calls, unless
+ // we have to consider interprocedural aliasing.
+ if (!Interprocedural)
+ if ((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
+ (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1))))
+ return NoAlias;
// Most objects can't alias null.
if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
@@ -733,17 +789,13 @@
// If one pointer is the result of a call/invoke or load and the other is a
// non-escaping local object, then we know the object couldn't escape to a
- // point where the call could return it. The load case works because
- // isNonEscapingLocalObject considers all stores to be escapes (it
- // passes true for the StoreCaptures argument to PointerMayBeCaptured).
+ // point where the call could return it.
if (O1 != O2) {
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1) || isa<LoadInst>(O1) ||
- isa<Argument>(O1)) &&
- isNonEscapingLocalObject(O2))
+ if (isEscapeSource(O1, Interprocedural) &&
+ isNonEscapingLocalObject(O2, Interprocedural))
return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2) || isa<LoadInst>(O2) ||
- isa<Argument>(O2)) &&
- isNonEscapingLocalObject(O1))
+ if (isEscapeSource(O2, Interprocedural) &&
+ isNonEscapingLocalObject(O1, Interprocedural))
return NoAlias;
}
@@ -776,3 +828,33 @@
// Make sure that anything that uses AliasAnalysis pulls in this file.
DEFINING_FILE_FOR(BasicAliasAnalysis)
+
+//===----------------------------------------------------------------------===//
+// InterproceduralBasicAliasAnalysis Pass
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// InterproceduralBasicAliasAnalysis - This is similar to basicaa, except
+ /// that it properly supports queries to values which live in different
+ /// functions.
+ ///
+ /// Note that we don't currently take this to the extreme, analyzing all
+ /// call sites of a function to answer a query about an Argument.
+ ///
+ struct InterproceduralBasicAliasAnalysis : public BasicAliasAnalysis {
+ static char ID; // Class identification, replacement for typeinfo
+ InterproceduralBasicAliasAnalysis() : BasicAliasAnalysis(&ID, true) {}
+ };
+}
+
+// Register this pass...
+char InterproceduralBasicAliasAnalysis::ID = 0;
+static RegisterPass<InterproceduralBasicAliasAnalysis>
+W("interprocedural-basic-aa", "Interprocedural Basic Alias Analysis", false, true);
+
+// Declare that we implement the AliasAnalysis interface
+static RegisterAnalysisGroup<AliasAnalysis> Z(W);
+
+ImmutablePass *llvm::createInterproceduralBasicAliasAnalysisPass() {
+ return new InterproceduralBasicAliasAnalysis();
+}