Add getters to access string attributes of arguments/return values

[apilipenko]

Summary

Add missing getters to access string attributes of arguments/return values.

[sanjoy]

Can you please (briefly) comment on what this will be used for?

[apilipenko]

In D10872#198351, @sanjoy wrote:

Can you please (briefly) comment on what this will be used for?

We are going to use these attributes along with metadata on loads to express higher level language types in IR. The idea of external types is similar to the TBAA types attached to load/store instructions.

[reames]

Artur,

Offline, we talked about the fact that this patch is actually two related parts. One is fixing a bug where the IR format doesn't properly parse our own output for a feature also supported in bitcode. The second is adding a set of extra accessors.

Could you split the first part into a new review with a clear description of what's going on? I doubt folks realized what this review actually contained from the original description. I certainly didn't.

[apilipenko]

Split into two patches. Parser part is moved to D11058.

include/llvm/IR/Argument.h

public:
 
   /// \brief Return true if this argument has the sext attribute on it in its
   /// containing function.
   bool hasSExtAttr() const;
 
   /// \brief Add a Attribute to an argument.
   void addAttr(AttributeSet AS);
 
+  /// \brief Return the attribute object for the given attribute kind.
+  Attribute getAttr(StringRef Kind) const;
+
+  /// \brief Return true if this argument has the attribute of the
+  /// specified kind.
+  bool hasAttr(StringRef Kind) const;
+
   /// \brief Remove a Attribute from an argument.
   void removeAttr(AttributeSet AS);
 
   /// \brief Method for support type inquiry through isa, cast, and
   /// dyn_cast.
   static inline bool classof(const Value *V) {
     return V->getValueID() == ArgumentVal;
   }
 };
 
 } // End llvm namespace
 
 #endif

include/llvm/IR/Function.h

public:
   }
   
   /// @brief Extract the number of dereferenceable_or_null bytes for a call or
   /// parameter (0=unknown).
   uint64_t getDereferenceableOrNullBytes(unsigned i) const {
     return AttributeSets.getDereferenceableOrNullBytes(i);
   }
   
+  /// \brief Return the attribute object that exists at the given index.
+  Attribute getAttribute(unsigned i, StringRef Kind) const {
+    return AttributeSets.getAttribute(i, Kind);
+  }
+
+  /// \brief Return true if attribute exists at the given index.
+  bool hasAttribute(unsigned i, StringRef Kind) const {
+    return AttributeSets.hasAttribute(i, Kind);
+  }
+
   /// @brief Determine if the function does not access memory.
   bool doesNotAccessMemory() const {
     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
                                       Attribute::ReadNone);
   }
   void setDoesNotAccessMemory() {
     addFnAttr(Attribute::ReadNone);
   }

lib/IR/Function.cpp

void Argument::addAttr(AttributeSet AS) {
   assert(AS.getNumSlots() <= 1 &&
          "Trying to add more than one attribute set to an argument!");
   AttrBuilder B(AS, AS.getSlotIndex(0));
   getParent()->addAttributes(getArgNo() + 1,
                              AttributeSet::get(Parent->getContext(),
                                                getArgNo() + 1, B));
 }
 
+Attribute Argument::getAttr(StringRef Kind) const {
+  return getParent()->getAttribute(getArgNo()+1, Kind);
+}
+
+bool Argument::hasAttr(StringRef Kind) const {
+  return getParent()->hasAttribute(getArgNo()+1, Kind);
+}
+
 /// removeAttr - Remove attributes from an argument.
 void Argument::removeAttr(AttributeSet AS) {
   assert(AS.getNumSlots() <= 1 &&
          "Trying to remove more than one attribute set from an argument!");
   AttrBuilder B(AS, AS.getSlotIndex(0));
   getParent()->removeAttributes(getArgNo() + 1,
                                 AttributeSet::get(Parent->getContext(),
                                                   getArgNo() + 1, B));