This patch aims to reduce compile time in LegalizeTypes by using Smal…

…lDenseMap,

with an initial number of elements,  instead of DenseMap, which has
zero initial elements, in order to avoid the copying of elements
when the size changes and to avoid allocating space every time
LegalizeTypes is run. This patch will not affect the memory footprint,
because DenseMap will increase the element size to 64
when the first element is added.

Patch by Wan Xiaofei.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173448 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/LegalizeTypes.h

@@ -80,35 +80,35 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
 
   /// PromotedIntegers - For integer nodes that are below legal width, this map
   /// indicates what promoted value to use.
-  DenseMap<SDValue, SDValue> PromotedIntegers;
+  SmallDenseMap<SDValue, SDValue, 8> PromotedIntegers;
 
   /// ExpandedIntegers - For integer nodes that need to be expanded this map
   /// indicates which operands are the expanded version of the input.
-  DenseMap<SDValue, std::pair<SDValue, SDValue> > ExpandedIntegers;
+  SmallDenseMap<SDValue, std::pair<SDValue, SDValue>, 8> ExpandedIntegers;
 
   /// SoftenedFloats - For floating point nodes converted to integers of
   /// the same size, this map indicates the converted value to use.
-  DenseMap<SDValue, SDValue> SoftenedFloats;
+  SmallDenseMap<SDValue, SDValue, 8> SoftenedFloats;
 
   /// ExpandedFloats - For float nodes that need to be expanded this map
   /// indicates which operands are the expanded version of the input.
-  DenseMap<SDValue, std::pair<SDValue, SDValue> > ExpandedFloats;
+  SmallDenseMap<SDValue, std::pair<SDValue, SDValue>, 8> ExpandedFloats;
 
   /// ScalarizedVectors - For nodes that are <1 x ty>, this map indicates the
   /// scalar value of type 'ty' to use.
-  DenseMap<SDValue, SDValue> ScalarizedVectors;
+  SmallDenseMap<SDValue, SDValue, 8> ScalarizedVectors;
 
   /// SplitVectors - For nodes that need to be split this map indicates
   /// which operands are the expanded version of the input.
-  DenseMap<SDValue, std::pair<SDValue, SDValue> > SplitVectors;
+  SmallDenseMap<SDValue, std::pair<SDValue, SDValue>, 8> SplitVectors;
 
   /// WidenedVectors - For vector nodes that need to be widened, indicates
   /// the widened value to use.
-  DenseMap<SDValue, SDValue> WidenedVectors;
+  SmallDenseMap<SDValue, SDValue, 8> WidenedVectors;
 
   /// ReplacedValues - For values that have been replaced with another,
   /// indicates the replacement value to use.
-  DenseMap<SDValue, SDValue> ReplacedValues;
+  SmallDenseMap<SDValue, SDValue, 8> ReplacedValues;
 
   /// Worklist - This defines a worklist of nodes to process.  In order to be
   /// pushed onto this worklist, all operands of a node must have already been

lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -40,7 +40,7 @@ class VectorLegalizer {
   /// LegalizedNodes - For nodes that are of legal width, and that have more
   /// than one use, this map indicates what regularized operand to use.  This
   /// allows us to avoid legalizing the same thing more than once.
-  DenseMap<SDValue, SDValue> LegalizedNodes;
+  SmallDenseMap<SDValue, SDValue, 64> LegalizedNodes;
 
   // Adds a node to the translation cache
   void AddLegalizedOperand(SDValue From, SDValue To) {