[llvm-commits] [123559] Don't create useless bitcast instructions.

[clattner at apple.com]

Revision: 123559
Author:   clattner
Date:     2007-02-07 13:53:56 -0800 (Wed, 07 Feb 2007)

Log Message:
-----------
Don't create useless bitcast instructions.  Patch by Reid Spencer!

Modified Paths:
--------------
    apple-local/branches/llvm/gcc/llvm-convert.cpp

Modified: apple-local/branches/llvm/gcc/llvm-convert.cpp
===================================================================
--- apple-local/branches/llvm/gcc/llvm-convert.cpp	2007-02-07 19:31:44 UTC (rev 123558)
+++ apple-local/branches/llvm/gcc/llvm-convert.cpp	2007-02-07 21:53:56 UTC (rev 123559)
@@ -708,7 +708,10 @@
 /// CastToType - Cast the specified value to the specified type if it is
 /// not already that type.
 Value *TreeToLLVM::CastToType(unsigned opcode, Value *V, const Type* Ty) {
-  if (V->getType() == Ty) return V;
+  // Eliminate useless casts of a type to itself.
+  if (V->getType() == Ty) 
+    return V;
+
   if (Constant *C = dyn_cast<Constant>(V))
     return ConstantExpr::getCast(Instruction::CastOps(opcode), C, Ty);
   
@@ -725,28 +728,48 @@
 /// assumptions about the types of the arguments. This creates an inferred cast.
 Value *TreeToLLVM::CastToAnyType(Value *V, bool VisSigned, 
                                  const Type* Ty, bool TyIsSigned) {
-  Instruction::CastOps opcode = CastInst::getCastOpcode(V, VisSigned, Ty, 
-                                                        TyIsSigned);
-  return CastToType(opcode, V, Ty);
+  // Eliminate useless casts of a type to itself.
+  if (V->getType() == Ty)
+    return V;
+
+  // The types are different so we must cast. Use getCastOpcode to create an
+  // inferred cast opcode.
+  Instruction::CastOps opc = 
+    CastInst::getCastOpcode(V, VisSigned, Ty, TyIsSigned);
+
+  // Generate the cast and return it.
+  return CastToType(opc, V, Ty);
 }
 
 /// CastToUIntType - Cast the specified value to the specified type assuming
 /// that the value and type are unsigned integer types.
 Value *TreeToLLVM::CastToUIntType(Value *V, const Type* Ty) {
+  // Eliminate useless casts of a type to itself.
+  if (V->getType() == Ty)
+    return V;
+
   unsigned SrcBits = V->getType()->getPrimitiveSizeInBits();
   unsigned DstBits = Ty->getPrimitiveSizeInBits();
-  Instruction::CastOps opcode = (SrcBits == DstBits ? Instruction::BitCast :
-      (SrcBits > DstBits ? Instruction::Trunc : Instruction::ZExt));
+  assert(SrcBits != DstBits && "Types are different but have same #bits?");
+
+  Instruction::CastOps opcode = 
+    (SrcBits > DstBits ? Instruction::Trunc : Instruction::ZExt);
   return CastToType(opcode, V, Ty);
 }
 
 /// CastToSIntType - Cast the specified value to the specified type assuming
 /// that the value and type are signed integer types.
 Value *TreeToLLVM::CastToSIntType(Value *V, const Type* Ty) {
+  // Eliminate useless casts of a type to itself.
+  if (V->getType() == Ty)
+    return V;
+
   unsigned SrcBits = V->getType()->getPrimitiveSizeInBits();
   unsigned DstBits = Ty->getPrimitiveSizeInBits();
-  Instruction::CastOps opcode = (SrcBits == DstBits ? Instruction::BitCast :
-      (SrcBits > DstBits ? Instruction::Trunc : Instruction::SExt));
+  assert(SrcBits != DstBits && "Types are different but have same #bits?");
+
+  Instruction::CastOps opcode = 
+    (SrcBits > DstBits ? Instruction::Trunc : Instruction::SExt);
   return CastToType(opcode, V, Ty);
 }