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authorChris Lattner <sabre@nondot.org>2001-12-13 00:43:03 +0000
committerChris Lattner <sabre@nondot.org>2001-12-13 00:43:03 +0000
commit9a49b210c1ae2c619ecd969b5ec17a68690928a9 (patch)
treed14ae9d5cecaa497dcd307278357681517c334a4
parent82d18aa0e42a4858c2cb7c15934cc3e567432490 (diff)
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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
-rw-r--r--include/llvm/InstrTypes.h12
-rw-r--r--lib/VMCore/iOperators.cpp26
2 files changed, 34 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; }
diff --git a/lib/VMCore/iOperators.cpp b/lib/VMCore/iOperators.cpp
index 22b6052..cb53d5e 100644
--- a/lib/VMCore/iOperators.cpp
+++ b/lib/VMCore/iOperators.cpp
@@ -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