Rewrite the removeAttr() method.

This now uses the AttributeSet object instead of the Attribute /
AttributeWithIndex objects. It's fairly simple now. It goes through all of the
subsets before the one we're modifying, adds them to the new set. It then adds
the modified subset (with the requested attributes removed). And then adds the
rest of the subsets.

llvm-svn: 173660

llvm/include/llvm/IR/Attributes.h

@@ -216,16 +216,6 @@ private:
   /// for the result are denoted with Idx = 0.
   Attribute getAttributes(unsigned Idx) const;
 
-  /// \brief Add the specified attribute at the specified index to this
-  /// attribute list.  Since attribute lists are immutable, this returns the new
-  /// list.
-  AttributeSet addAttr(LLVMContext &C, unsigned Idx, AttributeSet Attrs) const;
-
-  /// \brief Remove the specified attribute at the specified index from this
-  /// attribute list.  Since attribute lists are immutable, this returns the new
-  /// list.
-  AttributeSet removeAttr(LLVMContext &C, unsigned Idx, Attribute Attrs) const;
-
   /// \brief Create an AttributeSet from the AttributeWithIndex structures.
   /// N.B. this is only temporary. It will be disappearing in the future.
   static AttributeSet get(LLVMContext &C, ArrayRef<AttributeWithIndex> Attrs);

llvm/lib/IR/Attributes.cpp

@@ -771,16 +771,11 @@ bool AttributeSet::hasAttrSomewhere(Attribute::AttrKind Attr) const {
 
 AttributeSet AttributeSet::addAttribute(LLVMContext &C, unsigned Idx,
                                         Attribute::AttrKind Attr) const {
-  return addAttr(C, Idx, AttributeSet::get(C, Idx, Attr));
+  return addAttributes(C, Idx, AttributeSet::get(C, Idx, Attr));
 }
 
 AttributeSet AttributeSet::addAttributes(LLVMContext &C, unsigned Idx,
                                          AttributeSet Attrs) const {
-  return addAttr(C, Idx, Attrs);
-}
-
-AttributeSet AttributeSet::addAttr(LLVMContext &C, unsigned Idx,
-                                   AttributeSet Attrs) const {
   if (!pImpl) return Attrs;
   if (!Attrs.pImpl) return *this;
 
@@ -830,51 +825,54 @@ AttributeSet AttributeSet::addAttr(LLVMContext &C, unsigned Idx,
 
 AttributeSet AttributeSet::removeAttribute(LLVMContext &C, unsigned Idx,
                                            Attribute::AttrKind Attr) const {
-  return removeAttr(C, Idx, Attribute::get(C, Attr));
+  return removeAttributes(C, Idx, AttributeSet::get(C, Idx, Attr));
 }
 
 AttributeSet AttributeSet::removeAttributes(LLVMContext &C, unsigned Idx,
                                             AttributeSet Attrs) const {
-  return removeAttr(C, Idx, Attrs.getAttributes(Idx));
-}
+  if (!pImpl) return AttributeSet();
+  if (!Attrs.pImpl) return *this;
 
-AttributeSet AttributeSet::removeAttr(LLVMContext &C, unsigned Idx,
-                                      Attribute Attrs) const {
 #ifndef NDEBUG
   // FIXME it is not obvious how this should work for alignment.
   // For now, say we can't pass in alignment, which no current use does.
-  assert(!Attrs.hasAttribute(Attribute::Alignment) &&
-         "Attempt to exclude alignment!");
+  assert(!Attrs.hasAttribute(Idx, Attribute::Alignment) &&
+         "Attempt to change alignment!");
 #endif
-  if (pImpl == 0) return AttributeSet();
 
-  Attribute OldAttrs = getAttributes(Idx);
-  AttrBuilder NewAttrs =
-    AttrBuilder(OldAttrs).removeAttributes(Attrs);
-  if (NewAttrs == AttrBuilder(OldAttrs))
-    return *this;
+  // Add the attribute slots before the one we're trying to add.
+  SmallVector<AttributeSet, 4> AttrSet;
+  uint64_t NumAttrs = pImpl->getNumAttributes();
+  AttributeSet AS;
+  uint64_t LastIndex = 0;
+  for (unsigned I = 0, E = NumAttrs; I != E; ++I) {
+    if (getSlotIndex(I) >= Idx) {
+      if (getSlotIndex(I) == Idx) AS = getSlotAttributes(LastIndex++);
+      break;
+    }
+    LastIndex = I + 1;
+    AttrSet.push_back(getSlotAttributes(I));
+  }
 
-  SmallVector<AttributeWithIndex, 8> NewAttrList;
-  ArrayRef<AttributeWithIndex> OldAttrList = pImpl->getAttributes();
-  unsigned i = 0, e = OldAttrList.size();
+  // Now add the attribute into the correct slot. There may already be an
+  // AttributeSet there.
+  AttrBuilder B(AS, Idx);
 
-  // Copy attributes for arguments before this one.
-  for (; i != e && OldAttrList[i].Index < Idx; ++i)
-    NewAttrList.push_back(OldAttrList[i]);
+  for (unsigned I = 0, E = Attrs.pImpl->getNumAttributes(); I != E; ++I)
+    if (Attrs.getSlotIndex(I) == Idx) {
+      for (AttributeSetImpl::const_iterator II = Attrs.pImpl->begin(I),
+             IE = Attrs.pImpl->end(I); II != IE; ++II)
+        B.removeAttributes(*II);
+      break;
+    }
 
-  // If there are attributes already at this index, merge them in.
-  assert(OldAttrList[i].Index == Idx && "Attribute isn't set?");
-  Attrs = Attribute::get(C, AttrBuilder(OldAttrList[i].Attrs).
-                          removeAttributes(Attrs));
-  ++i;
-  if (Attrs.hasAttributes()) // If any attributes left for this param, add them.
-    NewAttrList.push_back(AttributeWithIndex::get(Idx, Attrs));
+  AttrSet.push_back(AttributeSet::get(C, Idx, B));
 
-  // Copy attributes for arguments after this one.
-  NewAttrList.insert(NewAttrList.end(),
-                     OldAttrList.begin()+i, OldAttrList.end());
+  // Add the remaining attribute slots.
+  for (unsigned I = LastIndex, E = NumAttrs; I < E; ++I)
+    AttrSet.push_back(getSlotAttributes(I));
 
-  return get(C, NewAttrList);
+  return get(C, AttrSet);
 }
 
 void AttributeSet::dump() const {