Add getReturnedArgOperand to Call/InvokeInst, CallSite

In order to make the optimizer smarter about using the 'returned' argument
attribute (generally, but motivated by my llvm.noalias intrinsic work), add a
utility function to Call/InvokeInst, and CallSite, to make it easy to get the
returned call argument (when one exists).

P.S. There is already an unfortunate amount of code duplication between
CallInst and InvokeInst, and this adds to it. We should probably clean that up
separately.

Differential Revision: http://reviews.llvm.org/D22204

llvm-svn: 275031

llvm/include/llvm/IR/Attributes.h

@@ -338,8 +338,10 @@ class AttributeSet {
   bool hasFnAttribute(Attribute::AttrKind Kind) const;
 
   /// \brief Return true if the specified attribute is set for at least one
-  /// parameter or for the return value.
-  bool hasAttrSomewhere(Attribute::AttrKind Kind) const;
+  /// parameter or for the return value. If Index is not nullptr, the index
+  /// of a parameter with the specified attribute is provided.
+  bool hasAttrSomewhere(Attribute::AttrKind Kind,
+                        unsigned *Index = nullptr) const;
 
   /// \brief Return the attribute object that exists at the given index.
   Attribute getAttribute(unsigned Index, Attribute::AttrKind Kind) const;

llvm/include/llvm/IR/CallSite.h

@@ -273,6 +273,10 @@ class CallSiteBase {
     CALLSITE_DELEGATE_GETTER(getArgOperand(i));
   }
 
+  ValTy *getReturnedArgOperand() const {
+    CALLSITE_DELEGATE_GETTER(getReturnedArgOperand());
+  }
+
   bool isInlineAsm() const {
     if (isCall())
       return cast<CallInst>(getInstruction())->isInlineAsm();

llvm/include/llvm/IR/Instructions.h

@@ -1597,6 +1597,10 @@ class CallInst : public Instruction,
     return getOperandUse(i);
   }
 
+  /// If one of the arguments has the 'returned' attribute, return its
+  /// operand value. Otherwise, return nullptr.
+  Value *getReturnedArgOperand() const;
+
   /// getCallingConv/setCallingConv - Get or set the calling convention of this
   /// function call.
   CallingConv::ID getCallingConv() const {
@@ -3566,6 +3570,10 @@ class InvokeInst : public TerminatorInst,
     return getOperandUse(i);
   }
 
+  /// If one of the arguments has the 'returned' attribute, return its
+  /// operand value. Otherwise, return nullptr.
+  Value *getReturnedArgOperand() const;
+
   /// getCallingConv/setCallingConv - Get or set the calling convention of this
   /// function call.
   CallingConv::ID getCallingConv() const {

llvm/lib/IR/Attributes.cpp

@@ -1108,14 +1108,17 @@ bool AttributeSet::hasFnAttribute(Attribute::AttrKind Kind) const {
   return pImpl && pImpl->hasFnAttribute(Kind);
 }
 
-bool AttributeSet::hasAttrSomewhere(Attribute::AttrKind Attr) const {
+bool AttributeSet::hasAttrSomewhere(Attribute::AttrKind Attr,
+                                    unsigned *Index) const {
   if (!pImpl) return false;
 
   for (unsigned I = 0, E = pImpl->getNumSlots(); I != E; ++I)
     for (AttributeSetImpl::iterator II = pImpl->begin(I),
            IE = pImpl->end(I); II != IE; ++II)
-      if (II->hasAttribute(Attr))
+      if (II->hasAttribute(Attr)) {
+        if (Index) *Index = pImpl->getSlotIndex(I);
         return true;
+      }
 
   return false;
 }

llvm/lib/IR/Instructions.cpp

@@ -331,6 +331,19 @@ CallInst *CallInst::Create(CallInst *CI, ArrayRef<OperandBundleDef> OpB,
   return NewCI;
 }
 
+Value *CallInst::getReturnedArgOperand() const {
+  unsigned Index;
+
+  if (AttributeList.hasAttrSomewhere(Attribute::Returned, &Index) && Index)
+    return getArgOperand(Index-1);
+  if (const Function *F = getCalledFunction())
+    if (F->getAttributes().hasAttrSomewhere(Attribute::Returned, &Index) &&
+        Index)
+      return getArgOperand(Index-1);
+
+  return nullptr;
+}
+
 void CallInst::addAttribute(unsigned i, Attribute::AttrKind Kind) {
   AttributeSet PAL = getAttributes();
   PAL = PAL.addAttribute(getContext(), i, Kind);
@@ -688,6 +701,19 @@ void InvokeInst::setSuccessorV(unsigned idx, BasicBlock *B) {
   return setSuccessor(idx, B);
 }
 
+Value *InvokeInst::getReturnedArgOperand() const {
+  unsigned Index;
+
+  if (AttributeList.hasAttrSomewhere(Attribute::Returned, &Index) && Index)
+    return getArgOperand(Index-1);
+  if (const Function *F = getCalledFunction())
+    if (F->getAttributes().hasAttrSomewhere(Attribute::Returned, &Index) &&
+        Index)
+      return getArgOperand(Index-1);
+
+  return nullptr;
+}
+
 bool InvokeInst::paramHasAttr(unsigned i, Attribute::AttrKind Kind) const {
   assert(i < (getNumArgOperands() + 1) && "Param index out of bounds!");