[llvm] 176c7f2 - [IR] Optimize adding attribute to AttributeList (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-01-22T11:30:21+01:00
New Revision: 176c7f22172eefddc9ff42dfae8a6015d4e017c6

URL: https://github.com/llvm/llvm-project/commit/176c7f22172eefddc9ff42dfae8a6015d4e017c6
DIFF: https://github.com/llvm/llvm-project/commit/176c7f22172eefddc9ff42dfae8a6015d4e017c6.diff

LOG: [IR] Optimize adding attribute to AttributeList (NFC)

When adding an enum attribute to an AttributeList, avoid going
through an AttrBuilder and instead directly add the attribute to
the correct set. Going through AttrBuilder is expensive, because
it requires all string attributes to be reconstructed.

This can be further improved by inserting the attribute at the
right position and using the AttributeSetNode::getSorted() API.

This recovers the small compile-time regression from D94633.

Added: 
    

Modified: 
    llvm/include/llvm/IR/Attributes.h
    llvm/lib/IR/Attributes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
index fbfe5854594f..b4056540663f 100644
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -399,6 +399,9 @@ class AttributeList {
 
   static AttributeList getImpl(LLVMContext &C, ArrayRef<AttributeSet> AttrSets);
 
+  AttributeList setAttributes(LLVMContext &C, unsigned Index,
+                              AttributeSet Attrs) const;
+
 public:
   AttributeList() = default;
 

diff  --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index ec2b83f614d9..b17673f14c9c 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -1272,9 +1272,11 @@ AttributeList AttributeList::get(LLVMContext &C,
 AttributeList AttributeList::addAttribute(LLVMContext &C, unsigned Index,
                                           Attribute::AttrKind Kind) const {
   if (hasAttribute(Index, Kind)) return *this;
-  AttrBuilder B;
-  B.addAttribute(Kind);
-  return addAttributes(C, Index, B);
+  AttributeSet Attrs = getAttributes(Index);
+  // TODO: Insert at correct position and avoid sort.
+  SmallVector<Attribute, 8> NewAttrs(Attrs.begin(), Attrs.end());
+  NewAttrs.push_back(Attribute::get(C, Kind));
+  return setAttributes(C, Index, AttributeSet::get(C, NewAttrs));
 }
 
 AttributeList AttributeList::addAttribute(LLVMContext &C, unsigned Index,
@@ -1292,6 +1294,16 @@ AttributeList AttributeList::addAttribute(LLVMContext &C, unsigned Index,
   return addAttributes(C, Index, B);
 }
 
+AttributeList AttributeList::setAttributes(LLVMContext &C, unsigned Index,
+                                           AttributeSet Attrs) const {
+  Index = attrIdxToArrayIdx(Index);
+  SmallVector<AttributeSet, 4> AttrSets(this->begin(), this->end());
+  if (Index >= AttrSets.size())
+    AttrSets.resize(Index + 1);
+  AttrSets[Index] = Attrs;
+  return AttributeList::getImpl(C, AttrSets);
+}
+
 AttributeList AttributeList::addAttributes(LLVMContext &C, unsigned Index,
                                            const AttrBuilder &B) const {
   if (!B.hasAttributes())
@@ -1309,16 +1321,9 @@ AttributeList AttributeList::addAttributes(LLVMContext &C, unsigned Index,
          "Attempt to change alignment!");
 #endif
 
-  Index = attrIdxToArrayIdx(Index);
-  SmallVector<AttributeSet, 4> AttrSets(this->begin(), this->end());
-  if (Index >= AttrSets.size())
-    AttrSets.resize(Index + 1);
-
-  AttrBuilder Merged(AttrSets[Index]);
+  AttrBuilder Merged(getAttributes(Index));
   Merged.merge(B);
-  AttrSets[Index] = AttributeSet::get(C, Merged);
-
-  return getImpl(C, AttrSets);
+  return setAttributes(C, Index, AttributeSet::get(C, Merged));
 }
 
 AttributeList AttributeList::addParamAttribute(LLVMContext &C,