[PATCH] Make one of the AttributeSet ctors keep the attribute list ordered by index.

[Peter Collingbourne]

http://llvm-reviews.chandlerc.com/D1265

Files:
  lib/IR/AttributeImpl.h
  lib/IR/Attributes.cpp
  unittests/IR/AttributesTest.cpp

Index: lib/IR/AttributeImpl.h
===================================================================
--- lib/IR/AttributeImpl.h
+++ lib/IR/AttributeImpl.h
@@ -200,6 +200,15 @@
   AttributeSetImpl(LLVMContext &C,
                    ArrayRef<std::pair<unsigned, AttributeSetNode *> > Attrs)
       : Context(C), NumAttrs(Attrs.size()) {
+#ifndef NDEBUG
+    if (Attrs.size() >= 2) {
+      for (const std::pair<unsigned, AttributeSetNode *> *i = Attrs.begin() + 1,
+                                                         *e = Attrs.end();
+           i != e; ++i) {
+        assert((i-1)->first <= i->first && "Attribute set not ordered!");
+      }
+    }
+#endif
     // There's memory after the node where we can store the entries in.
     std::copy(Attrs.begin(), Attrs.end(),
               reinterpret_cast<IndexAttrPair *>(this + 1));
Index: lib/IR/Attributes.cpp
===================================================================
--- lib/IR/Attributes.cpp
+++ lib/IR/Attributes.cpp
@@ -621,12 +621,30 @@
 
 AttributeSet AttributeSet::get(LLVMContext &C, ArrayRef<AttributeSet> Attrs) {
   if (Attrs.empty()) return AttributeSet();
+  if (Attrs.size() == 1) return Attrs[0];
 
   SmallVector<std::pair<unsigned, AttributeSetNode*>, 8> AttrNodeVec;
-  for (unsigned I = 0, E = Attrs.size(); I != E; ++I) {
+  AttributeSetImpl *A0 = Attrs[0].pImpl;
+  if (A0)
+    AttrNodeVec.append(A0->getNode(0), A0->getNode(A0->getNumAttributes()));
+  // Copy all attributes from Attrs into AttrNodeVec while keeping AttrNodeVec
+  // ordered by index.  Because we know that each list in Attrs is ordered by
+  // index we only need to merge each successive list in rather than doing a
+  // full sort.
+  for (unsigned I = 1, E = Attrs.size(); I != E; ++I) {
     AttributeSetImpl *AS = Attrs[I].pImpl;
     if (!AS) continue;
-    AttrNodeVec.append(AS->getNode(0), AS->getNode(AS->getNumAttributes()));
+    SmallVector<std::pair<unsigned, AttributeSetNode *>, 8>::iterator
+      ANVI = AttrNodeVec.begin(), ANVE;
+    for (const AttributeSetImpl::IndexAttrPair
+             *AI = AS->getNode(0),
+             *AE = AS->getNode(AS->getNumAttributes());
+         AI != AE; ++AI) {
+      ANVE = AttrNodeVec.end();
+      while (ANVI != ANVE && ANVI->first <= AI->first)
+        ++ANVI;
+      ANVI = AttrNodeVec.insert(ANVI, *AI) + 1;
+    }
   }
 
   return getImpl(C, AttrNodeVec);
Index: unittests/IR/AttributesTest.cpp
===================================================================
--- unittests/IR/AttributesTest.cpp
+++ unittests/IR/AttributesTest.cpp
@@ -31,4 +31,17 @@
   EXPECT_EQ(SetA, SetB);
 }
 
+TEST(Attributes, Ordering) {
+  LLVMContext C;
+
+  AttributeSet ASs[] = {
+    AttributeSet::get(C, 2, Attribute::ZExt),
+    AttributeSet::get(C, 1, Attribute::SExt)
+  };
+
+  AttributeSet SetA = AttributeSet::get(C, ASs);
+  AttributeSet SetB = SetA.removeAttributes(C, 1, ASs[1]);
+  EXPECT_NE(SetA, SetB);
+}
+
 } // end anonymous namespace
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