NFC. Introduce Value::isPointerDereferenceable
Extract a part of isDereferenceableAndAlignedPointer functionality to Value: Reviewed By: hfinkel, sanjoy Differential Revision: http://reviews.llvm.org/D17611 llvm-svn: 269190
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@ -511,6 +511,12 @@ public:
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/// dereferenceable up to the returned number of bytes.
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unsigned getPointerDereferenceableBytes(bool &CanBeNull) const;
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/// \brief Returns true if the pointer value is fully dereferenceable.
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///
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/// Sets CanBeNull to true if the pointer is either null or can be fully
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/// dereferenceable.
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bool isPointerDereferenceable(bool &CanBeNull) const;
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/// \brief Returns an alignment of the pointer value.
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///
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/// Returns an alignment which is either specified explicitly, e.g. via
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@ -91,9 +91,12 @@ static bool isDereferenceableAndAlignedPointer(
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// Note that it is not safe to speculate into a malloc'd region because
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// malloc may return null.
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// These are obviously ok if aligned.
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if (isa<AllocaInst>(V))
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bool CheckForNonNull;
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if (V->isPointerDereferenceable(CheckForNonNull)) {
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if (CheckForNonNull && !isKnownNonNullAt(V, CtxI, DT, TLI))
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return false;
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return isAligned(V, Align, DL);
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}
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// It's not always safe to follow a bitcast, for example:
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// bitcast i8* (alloca i8) to i32*
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@ -112,16 +115,6 @@ static bool isDereferenceableAndAlignedPointer(
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CtxI, DT, TLI, Visited);
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}
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// Global variables which can't collapse to null are ok.
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if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
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if (!GV->hasExternalWeakLinkage())
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return isAligned(V, Align, DL);
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// byval arguments are okay.
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if (const Argument *A = dyn_cast<Argument>(V))
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if (A->hasByValAttr())
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return isAligned(V, Align, DL);
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if (isDereferenceableFromAttribute(V, DL, CtxI, DT, TLI))
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return isAligned(V, Align, DL);
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@ -559,6 +559,29 @@ unsigned Value::getPointerDereferenceableBytes(bool &CanBeNull) const {
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return DerefBytes;
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}
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bool Value::isPointerDereferenceable(bool &CanBeNull) const {
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assert(getType()->isPointerTy() && "must be pointer");
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CanBeNull = false;
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// These are obviously ok.
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if (isa<AllocaInst>(this))
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return true;
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// Global variables which can't collapse to null are ok.
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// TODO: return true for those but set CanBeNull flag
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if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
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if (!GV->hasExternalWeakLinkage())
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return true;
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// byval arguments are okay.
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if (const Argument *A = dyn_cast<Argument>(this))
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if (A->hasByValAttr())
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return true;
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return false;
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}
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unsigned Value::getPointerAlignment(const DataLayout &DL) const {
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assert(getType()->isPointerTy() && "must be pointer");
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