[AttributeSet] Overload AttributeSet::addAttribute to reduce compile

time.

The new overloaded function is used when an attribute is added to a
large number of slots of an AttributeSet (for example, to function
parameters). This is much faster than calling AttributeSet::addAttribute
once per slot, because AttributeSet::getImpl (which calls
FoldingSet::FIndNodeOrInsertPos) is called only once per function
instead of once per slot.

With this commit, clang compiles a file which used to take over 22
minutes in just 13 seconds.

rdar://problem/23581000

Differential Revision: http://reviews.llvm.org/D15085

llvm-svn: 254491

llvm/include/llvm/IR/Attributes.h

@@ -227,6 +227,11 @@ class AttributeSet {
   AttributeSet addAttribute(LLVMContext &C, unsigned Index,
                             StringRef Kind, StringRef Value) const;
 
+  /// Add an attribute to the attribute set at the given indices. Because
+  /// attribute sets are immutable, this returns a new set.
+  AttributeSet addAttribute(LLVMContext &C, ArrayRef<unsigned> Indices,
+                            Attribute A) const;
+
   /// \brief Add attributes to the attribute set at the given index. Because
   /// attribute sets are immutable, this returns a new set.
   AttributeSet addAttributes(LLVMContext &C, unsigned Index,

llvm/lib/IR/Attributes.cpp

@@ -770,6 +770,36 @@ AttributeSet AttributeSet::addAttribute(LLVMContext &C, unsigned Index,
   return addAttributes(C, Index, AttributeSet::get(C, Index, B));
 }
 
+AttributeSet AttributeSet::addAttribute(LLVMContext &C,
+                                        ArrayRef<unsigned> Indices,
+                                        Attribute A) const {
+  unsigned I = 0, E = pImpl ? pImpl->getNumAttributes() : 0;
+  auto IdxI = Indices.begin(), IdxE = Indices.end();
+  SmallVector<AttributeSet, 4> AttrSet;
+
+  while (I != E && IdxI != IdxE) {
+    if (getSlotIndex(I) < *IdxI)
+      AttrSet.emplace_back(getSlotAttributes(I++));
+    else if (getSlotIndex(I) > *IdxI)
+      AttrSet.emplace_back(AttributeSet::get(C, std::make_pair(*IdxI++, A)));
+    else {
+      AttrBuilder B(getSlotAttributes(I), *IdxI);
+      B.addAttribute(A);
+      AttrSet.emplace_back(AttributeSet::get(C, *IdxI, B));
+      ++I;
+      ++IdxI;
+    }
+  }
+
+  while (I != E)
+    AttrSet.emplace_back(getSlotAttributes(I++));
+
+  while (IdxI != IdxE)
+    AttrSet.emplace_back(AttributeSet::get(C, std::make_pair(*IdxI++, A)));
+
+  return get(C, AttrSet);
+}
+
 AttributeSet AttributeSet::addAttributes(LLVMContext &C, unsigned Index,
                                          AttributeSet Attrs) const {
   if (!pImpl) return Attrs;

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -1942,20 +1942,27 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
   // Mark any parameters that are known to be non-null with the nonnull
   // attribute.  This is helpful for inlining calls to functions with null
   // checks on their arguments.
+  SmallVector<unsigned, 4> Indices;
   unsigned ArgNo = 0;
+
   for (Value *V : CS.args()) {
     if (V->getType()->isPointerTy() && !CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
-        isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {
-      AttributeSet AS = CS.getAttributes();
-      AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
-                           Attribute::NonNull);
-      CS.setAttributes(AS);
-      Changed = true;
-    }
+        isKnownNonNullAt(V, CS.getInstruction(), DT, TLI))
+      Indices.push_back(ArgNo + 1);
     ArgNo++;
   }
+
   assert(ArgNo == CS.arg_size() && "sanity check");
 
+  if (!Indices.empty()) {
+    AttributeSet AS = CS.getAttributes();
+    LLVMContext &Ctx = CS.getInstruction()->getContext();
+    AS = AS.addAttribute(Ctx, Indices,
+                         Attribute::get(Ctx, Attribute::NonNull));
+    CS.setAttributes(AS);
+    Changed = true;
+  }
+
   // If the callee is a pointer to a function, attempt to move any casts to the
   // arguments of the call/invoke.
   Value *Callee = CS.getCalledValue();

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

@@ -307,27 +307,31 @@ bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
 /// processCallSite - Infer nonnull attributes for the arguments at the
 /// specified callsite.
 bool CorrelatedValuePropagation::processCallSite(CallSite CS) {
-  bool Changed = false;
-
+  SmallVector<unsigned, 4> Indices;
   unsigned ArgNo = 0;
+
   for (Value *V : CS.args()) {
     PointerType *Type = dyn_cast<PointerType>(V->getType());
 
     if (Type && !CS.paramHasAttr(ArgNo + 1, Attribute::NonNull) &&
         LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
                             ConstantPointerNull::get(Type),
-                            CS.getInstruction()) == LazyValueInfo::False) {
-      AttributeSet AS = CS.getAttributes();
-      AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo + 1,
-                           Attribute::NonNull);
-      CS.setAttributes(AS);
-      Changed = true;
-    }
+                            CS.getInstruction()) == LazyValueInfo::False)
+      Indices.push_back(ArgNo + 1);
     ArgNo++;
   }
+
   assert(ArgNo == CS.arg_size() && "sanity check");
 
-  return Changed;
+  if (Indices.empty())
+    return false;
+
+  AttributeSet AS = CS.getAttributes();
+  LLVMContext &Ctx = CS.getInstruction()->getContext();
+  AS = AS.addAttribute(Ctx, Indices, Attribute::get(Ctx, Attribute::NonNull));
+  CS.setAttributes(AS);
+
+  return true;
 }
 
 Constant *CorrelatedValuePropagation::getConstantAt(Value *V, Instruction *At) {