Add an experimental early if-conversion pass, off by default.

[oota-llvm.git] / include / llvm / Target / TargetInstrInfo.h

diff --git a/include/llvm/Target/TargetInstrInfo.h b/include/llvm/Target/TargetInstrInfo.h
index f096946b382771f4a4812dfbd5c55dcd14b36f9f..73efc507fab6654a9f31c1f20bffe15a3d0a9ea9 100644 (file)
--- a/include/llvm/Target/TargetInstrInfo.h
+++ b/include/llvm/Target/TargetInstrInfo.h
@@ -369,6 +369,56 @@ public:
     return false;
   }
 
+  /// canInsertSelect - Return true if it is possible to insert a select
+  /// instruction that chooses between TrueReg and FalseReg based on the
+  /// condition code in Cond.
+  ///
+  /// When successful, also return the latency in cycles from TrueReg,
+  /// FalseReg, and Cond to the destination register. The Cond latency should
+  /// compensate for a conditional branch being removed. For example, if a
+  /// conditional branch has a 3 cycle latency from the condition code read,
+  /// and a cmov instruction has a 2 cycle latency from the condition code
+  /// read, CondCycles should be returned as -1.
+  ///
+  /// @param MBB         Block where select instruction would be inserted.
+  /// @param Cond        Condition returned by AnalyzeBranch.
+  /// @param TrueReg     Virtual register to select when Cond is true.
+  /// @param FalseReg    Virtual register to select when Cond is false.
+  /// @param CondCycles  Latency from Cond+Branch to select output.
+  /// @param TrueCycles  Latency from TrueReg to select output.
+  /// @param FalseCycles Latency from FalseReg to select output.
+  virtual bool canInsertSelect(const MachineBasicBlock &MBB,
+                               const SmallVectorImpl<MachineOperand> &Cond,
+                               unsigned TrueReg, unsigned FalseReg,
+                               int &CondCycles,
+                               int &TrueCycles, int &FalseCycles) const {
+    return false;
+  }
+
+  /// insertSelect - Insert a select instruction into MBB before I that will
+  /// copy TrueReg to DstReg when Cond is true, and FalseReg to DstReg when
+  /// Cond is false.
+  ///
+  /// This function can only be called after canInsertSelect() returned true.
+  /// The condition in Cond comes from AnalyzeBranch, and it can be assumed
+  /// that the same flags or registers required by Cond are available at the
+  /// insertion point.
+  ///
+  /// @param MBB      Block where select instruction should be inserted.
+  /// @param I        Insertion point.
+  /// @param DL       Source location for debugging.
+  /// @param DstReg   Virtual register to be defined by select instruction.
+  /// @param Cond     Condition as computed by AnalyzeBranch.
+  /// @param TrueReg  Virtual register to copy when Cond is true.
+  /// @param FalseReg Virtual register to copy when Cons is false.
+  virtual void insertSelect(MachineBasicBlock &MBB,
+                            MachineBasicBlock::iterator I, DebugLoc DL,
+                            unsigned DstReg,
+                            const SmallVectorImpl<MachineOperand> &Cond,
+                            unsigned TrueReg, unsigned FalseReg) const {
+    llvm_unreachable("Target didn't implement TargetInstrInfo::insertSelect!");
+  }
+
   /// copyPhysReg - Emit instructions to copy a pair of physical registers.
   virtual void copyPhysReg(MachineBasicBlock &MBB,
                            MachineBasicBlock::iterator MI, DebugLoc DL,