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Swap operands now preserves the semantics of the binary operator by changing 

the opcode of the instruction if possible.

llvm-svn: 1444
This commit is contained in:
Chris Lattner 2001-12-13 00:43:03 +00:00
parent 25450e32c0
commit 156344c890
2 changed files with 34 additions and 4 deletions
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12
llvm/include/llvm/InstrTypes.h
View File

@ -127,10 +127,14 @@ public:
virtual const char *getOpcodeName() const = 0;
// swapOperands - Exchange the two operands to this instruction
void swapOperands() {
swap(Operands[0], Operands[1]);
}
// swapOperands - Exchange the two operands to this instruction.
// This instruction is safe to use on any binary instruction and
// does not modify the semantics of the instruction. If the
// instruction is order dependant (SetLT f.e.) the opcode is
// changed. If the instruction cannot be reversed (ie, it's a Div),
// then return true.
//
bool swapOperands();
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const BinaryOperator *) { return true; }

26
llvm/lib/VMCore/iOperators.cpp
View File

@ -53,6 +53,32 @@ BinaryOperator *BinaryOperator::create(BinaryOps Op, Value *S1, Value *S2,
}
}
// swapOperands - Exchange the two operands to this instruction. This
// instruction is safe to use on any binary instruction and does not
// modify the semantics of the instruction. If the instruction is
// order dependant (SetLT f.e.) the opcode is changed.
//
bool BinaryOperator::swapOperands() {
switch (getOpcode()) {
// Instructions that don't need opcode modification
case Add: case Mul:
case And: case Xor:
case Or:
case SetEQ: case SetNE:
break;
// Instructions that need opcode modification
case SetGT: iType = SetLT; break;
case SetLT: iType = SetGT; break;
case SetGE: iType = SetLE; break;
case SetLE: iType = SetGE; break;
// Error on the side of caution
default:
return true;
}
swap(Operands[0], Operands[1]);
return false;
}
//===----------------------------------------------------------------------===//
// GenericBinaryInst Class