Eliminate the explicit opcode field in ConstantExpr, using the SubclassData

field to hold it instead.  This shrinks memory usage for 176.gcc from
57628728 to 57598144 bytes, a small reduction of about 30K.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20047 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Constants.h b/include/llvm/Constants.h
index d22270e87128ca2c301649b58c05442196ce3ceb..91e7b208a21b08ce335b214e93e68272c2a20537 100644 (file)
--- a/include/llvm/Constants.h
+++ b/include/llvm/Constants.h
@@ -510,26 +510,22 @@ public:
 
 
 /// ConstantExpr - a constant value that is initialized with an expression using
-/// other constant values.  This is only used to represent values that cannot be
-/// evaluated at compile-time (e.g., something derived from an address) because
-/// it does not have a mechanism to store the actual value.  Use the appropriate
-/// Constant subclass above for known constants.
+/// other constant values.
 ///
+/// This class uses the standard Instruction opcodes to define the various
+/// constant expressions.  The Opcode field for the ConstantExpr class is
+/// maintained in the Value::SubclassData field.
 class ConstantExpr : public Constant {
-  unsigned iType;      // Operation type (an Instruction opcode)
   friend struct ConstantCreator<ConstantExpr,Type,
                             std::pair<unsigned, std::vector<Constant*> > >;
   friend struct ConvertConstantType<ConstantExpr, Type>;
   
 protected:
   ConstantExpr(const Type *Ty, unsigned Opcode, Use *Ops, unsigned NumOps)
-    : Constant(Ty, ConstantExprVal, Ops, NumOps), iType(Opcode) {}
-
-  // Select instruction creation ctor
-  ConstantExpr(Constant *C, Constant *V1, Constant *V2);
-  // GEP instruction creation ctor
-  ConstantExpr(Constant *C, const std::vector<Constant*> &IdxList,
-               const Type *DestTy);
+    : Constant(Ty, ConstantExprVal, Ops, NumOps) {
+    // Operation type (an Instruction opcode) is stored as the SubclassData.
+    SubclassData = Opcode; 
+  }
 
   // These private methods are used by the type resolution code to create
   // ConstantExprs in intermediate forms.
@@ -609,7 +605,7 @@ public:
   virtual bool isNullValue() const { return false; }
   
   /// getOpcode - Return the opcode at the root of this constant expression
-  unsigned getOpcode() const { return iType; }
+  unsigned getOpcode() const { return SubclassData; }
 
   /// getOpcodeName - Return a string representation for an opcode.
   const char *getOpcodeName() const;