[llvm] r281955 - [RegisterBankInfo] Avoid heap allocation in InstructionMapping.

[Quentin Colombet via llvm-commits]

Author: qcolombet
Date: Mon Sep 19 19:48:44 2016
New Revision: 281955

URL: http://llvm.org/viewvc/llvm-project?rev=281955&view=rev
Log:
[RegisterBankInfo] Avoid heap allocation in InstructionMapping.

Use SmallVector instead of dynamically allocated arrays for the mapping of the
operands in the InstructionMapping. That way we avoid heap allocation for most
of the cases. Ultimately, we should not have to rely on such tricky, the
instances of InstructionMapping would be TableGen'ed.

This improves the compilation time of the RegBankSelect pass.

Modified:
    llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h

Modified: llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h?rev=281955&r1=281954&r2=281955&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h Mon Sep 19 19:48:44 2016
@@ -109,7 +109,8 @@ public:
     /// Cost of this mapping.
     unsigned Cost;
     /// Mapping of all the operands.
-    std::unique_ptr<ValueMapping[]> OperandsMapping;
+    /// Note: Use a SmallVector to avoid heap allocation in most cases.
+    SmallVector<ValueMapping, 8> OperandsMapping;
     /// Number of operands.
     unsigned NumOperands;
 
@@ -131,7 +132,7 @@ public:
         : ID(ID), Cost(Cost), NumOperands(NumOperands) {
       assert(getID() != InvalidMappingID &&
              "Use the default constructor for invalid mapping");
-      OperandsMapping.reset(new ValueMapping[getNumOperands()]);
+      OperandsMapping.resize(getNumOperands());
     }
 
     /// Default constructor.