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Edit and clarify comments for TargetInstrInfo methods: 

None of the existing implementations of commuteInstruction create new
instructions unless the NewMI parameter is true, but the comment had
implied otherwise.

findCommutedOpIndices returns false, not true, when it doesn't know
how to commute the instruction.

llvm-svn: 106761
This commit is contained in:
Bob Wilson 2010-06-24 16:48:26 +00:00
parent 5235cc2c25
commit 1cfe454c87
1 changed files with 9 additions and 13 deletions
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22
llvm/include/llvm/Target/TargetInstrInfo.h
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@ -237,23 +237,19 @@ public:
return 0;
}
/// commuteInstruction - If a target has any instructions that are commutable,
/// but require converting to a different instruction or making non-trivial
/// changes to commute them, this method can overloaded to do this. The
/// default implementation of this method simply swaps the first two operands
/// of MI and returns it.
///
/// If a target wants to make more aggressive changes, they can construct and
/// return a new machine instruction. If an instruction cannot commute, it
/// can also return null.
///
/// If NewMI is true, then a new machine instruction must be created.
///
/// commuteInstruction - If a target has any instructions that are
/// commutable but require converting to different instructions or making
/// non-trivial changes to commute them, this method can overloaded to do
/// that. The default implementation simply swaps the commutable operands.
/// If NewMI is false, MI is modified in place and returned; otherwise, a
/// new machine instruction is created and returned. Do not call this
/// method for a non-commutable instruction, but there may be some cases
/// where this method fails and returns null.
virtual MachineInstr *commuteInstruction(MachineInstr *MI,
bool NewMI = false) const = 0;
/// findCommutedOpIndices - If specified MI is commutable, return the two
/// operand indices that would swap value. Return true if the instruction
/// operand indices that would swap value. Return false if the instruction
/// is not in a form which this routine understands.
virtual bool findCommutedOpIndices(MachineInstr *MI, unsigned &SrcOpIdx1,
unsigned &SrcOpIdx2) const = 0;