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

the opcode of the instruction if possible.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1444 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 4 deletions

diff --git a/include/llvm/InstrTypes.h b/include/llvm/InstrTypes.h
index 54aab32..3d834e9 100644
--- a/include/llvm/InstrTypes.h
+++ b/include/llvm/InstrTypes.h
@@ -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; }