+ /// analyzeSelect - Analyze the given select instruction, returning true if
+ /// it cannot be understood. It is assumed that MI->isSelect() is true.
+ ///
+ /// When successful, return the controlling condition and the operands that
+ /// determine the true and false result values.
+ ///
+ /// Result = SELECT Cond, TrueOp, FalseOp
+ ///
+ /// Some targets can optimize select instructions, for example by predicating
+ /// the instruction defining one of the operands. Such targets should set
+ /// Optimizable.
+ ///
+ /// @param MI Select instruction to analyze.
+ /// @param Cond Condition controlling the select.
+ /// @param TrueOp Operand number of the value selected when Cond is true.
+ /// @param FalseOp Operand number of the value selected when Cond is false.
+ /// @param Optimizable Returned as true if MI is optimizable.
+ /// @returns False on success.
+ virtual bool analyzeSelect(const MachineInstr *MI,
+ SmallVectorImpl<MachineOperand> &Cond,
+ unsigned &TrueOp, unsigned &FalseOp,
+ bool &Optimizable) const {
+ assert(MI && MI->isSelect() && "MI must be a select instruction");
+ return true;
+ }
+
+ /// optimizeSelect - Given a select instruction that was understood by
+ /// analyzeSelect and returned Optimizable = true, attempt to optimize MI by
+ /// merging it with one of its operands. Returns NULL on failure.
+ ///
+ /// When successful, returns the new select instruction. The client is
+ /// responsible for deleting MI.
+ ///
+ /// If both sides of the select can be optimized, PreferFalse is used to pick
+ /// a side.
+ ///
+ /// @param MI Optimizable select instruction.
+ /// @param PreferFalse Try to optimize FalseOp instead of TrueOp.
+ /// @returns Optimized instruction or NULL.
+ virtual MachineInstr *optimizeSelect(MachineInstr *MI,
+ bool PreferFalse = false) const {
+ // This function must be implemented if Optimizable is ever set.
+ llvm_unreachable("Target must implement TargetInstrInfo::optimizeSelect!");
+ }
+