#include "llvm/ParameterAttributes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
-#include "llvm/Intrinsics.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallVector.h"
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
};
+} // End of anonymous namespace
- // Register this pass...
- char NoAA::ID = 0;
- RegisterPass<NoAA>
- U("no-aa", "No Alias Analysis (always returns 'may' alias)");
+// Register this pass...
+char NoAA::ID = 0;
+static RegisterPass<NoAA>
+U("no-aa", "No Alias Analysis (always returns 'may' alias)", true, true);
- // Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis> V(U);
-} // End of anonymous namespace
+// Declare that we implement the AliasAnalysis interface
+static RegisterAnalysisGroup<AliasAnalysis> V(U);
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
const Type *BasePtr2Ty,
Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size);
};
+} // End of anonymous namespace
- // Register this pass...
- char BasicAliasAnalysis::ID = 0;
- RegisterPass<BasicAliasAnalysis>
- X("basicaa", "Basic Alias Analysis (default AA impl)");
+// Register this pass...
+char BasicAliasAnalysis::ID = 0;
+static RegisterPass<BasicAliasAnalysis>
+X("basicaa", "Basic Alias Analysis (default AA impl)", false, true);
- // Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis, true> Y(X);
-} // End of anonymous namespace
+// Declare that we implement the AliasAnalysis interface
+static RegisterAnalysisGroup<AliasAnalysis, true> Y(X);
ImmutablePass *llvm::createBasicAliasAnalysisPass() {
return new BasicAliasAnalysis();
}
-// getUnderlyingObject - This traverses the use chain to figure out what object
-// the specified value points to. If the value points to, or is derived from, a
-// unique object or an argument, return it.
+/// getUnderlyingObject - This traverses the use chain to figure out what object
+/// the specified value points to. If the value points to, or is derived from,
+/// a unique object or an argument, return it. This returns:
+/// Arguments, GlobalVariables, Functions, Allocas, Mallocs.
static const Value *getUnderlyingObject(const Value *V) {
if (!isa<PointerType>(V->getType())) return 0;
return true;
break; // next use.
case Instruction::BitCast:
- if (!isa<PointerType>(I->getType()))
- return true;
if (AddressMightEscape(I))
return true;
break; // next use
// If returned, the address will escape to calling functions, but no
// callees could modify it.
break; // next use
+ case Instruction::Call:
+ // If the call is to a few known safe intrinsics, we know that it does
+ // not escape
+ if (!isa<MemIntrinsic>(I))
+ return true;
+ break; // next use
default:
return true;
}
//
AliasAnalysis::ModRefResult
BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- if (!isa<Constant>(P))
- if (const AllocationInst *AI =
- dyn_cast_or_null<AllocationInst>(getUnderlyingObject(P))) {
- // Okay, the pointer is to a stack allocated object. If we can prove that
- // the pointer never "escapes", then we know the call cannot clobber it,
- // because it simply can't get its address.
- if (!AddressMightEscape(AI))
- return NoModRef;
+ if (!isa<Constant>(P)) {
+ const Value *Object = getUnderlyingObject(P);
+ // Allocations and byval arguments are "new" objects.
+ if (Object &&
+ (isa<AllocationInst>(Object) || isa<Argument>(Object))) {
+ // Okay, the pointer is to a stack allocated (or effectively so, for
+ // for noalias parameters) object. If the address of this object doesn't
+ // escape from this function body to a callee, then we know that no
+ // callees can mod/ref it unless they are actually passed it.
+ if (isa<AllocationInst>(Object) ||
+ cast<Argument>(Object)->hasByValAttr() ||
+ cast<Argument>(Object)->hasNoAliasAttr())
+ if (!AddressMightEscape(Object)) {
+ bool passedAsArg = false;
+ for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ CI != CE; ++CI)
+ if (isa<PointerType>((*CI)->getType()) &&
+ ( getUnderlyingObject(*CI) == P ||
+ alias(cast<Value>(CI), ~0U, P, ~0U) != NoAlias) )
+ passedAsArg = true;
+
+ if (!passedAsArg)
+ return NoModRef;
+ }
// If this is a tail call and P points to a stack location, we know that
// the tail call cannot access or modify the local stack.
- if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
- if (CI->isTailCall() && isa<AllocaInst>(AI))
- return NoModRef;
+ // We cannot exclude byval arguments here; these belong to the caller of
+ // the current function not to the current function, and a tail callee
+ // may reference them.
+ if (isa<AllocaInst>(Object))
+ if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
+ if (CI->isTailCall())
+ return NoModRef;
}
+ }
// The AliasAnalysis base class has some smarts, lets use them.
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
-static bool isNoAliasArgument(const Argument *Arg) {
- const Function *Func = Arg->getParent();
- const ParamAttrsList *Attr = Func->getParamAttrs();
- if (Attr) {
- unsigned Idx = 1;
- for (Function::const_arg_iterator I = Func->arg_begin(),
- E = Func->arg_end(); I != E; ++I, ++Idx) {
- if (&(*I) == Arg &&
- Attr->paramHasAttr(Idx, ParamAttr::NoAlias))
- return true;
- }
- }
- return false;
-}
-
// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
// as array references. Note that this function is heavily tail recursive.
// Hopefully we have a smart C++ compiler. :)
// If they are two different objects, and one is a noalias argument
// then they do not alias.
- if (O1 != O2 && isNoAliasArgument(O1Arg))
+ if (O1 != O2 && O1Arg->hasNoAliasAttr())
return NoAlias;
-
+
+ // Byval arguments can't alias globals or other arguments.
+ if (O1 != O2 && O1Arg->hasByValAttr()) return NoAlias;
+
// Otherwise, nothing is known...
}
// If they are two different objects, and one is a noalias argument
// then they do not alias.
- if (O1 != O2 && isNoAliasArgument(O2Arg))
+ if (O1 != O2 && O2Arg->hasNoAliasAttr())
return NoAlias;
+ // Byval arguments can't alias globals or other arguments.
+ if (O1 != O2 && O2Arg->hasByValAttr()) return NoAlias;
+
// Otherwise, nothing is known...
- } else if (O1 != O2) {
- if (!isa<Argument>(O1))
- // If they are two different objects, and neither is an argument,
- // we know that we have no alias...
- return NoAlias;
+ } else if (O1 != O2 && !isa<Argument>(O1)) {
+ // If they are two different objects, and neither is an argument,
+ // we know that we have no alias.
+ return NoAlias;
}
// If they are the same object, they we can look at the indexes. If they
// can't tell anything.
}
-
- if (!isa<Argument>(O1) && isa<ConstantPointerNull>(V2))
- return NoAlias; // Unique values don't alias null
+ // Unique values don't alias null, except non-byval arguments.
+ if (isa<ConstantPointerNull>(V2)) {
+ if (const Argument *O1Arg = dyn_cast<Argument>(O1)) {
+ if (O1Arg->hasByValAttr())
+ return NoAlias;
+ } else {
+ return NoAlias;
+ }
+ }
if (isa<GlobalVariable>(O1) ||
(isa<AllocationInst>(O1) &&
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