From c4f70d437df505e128e0debdf0c5f4ab5010e1b5 Mon Sep 17 00:00:00 2001 From: James Molloy Date: Wed, 12 Sep 2012 10:18:23 +0000 Subject: Add a function computeRegisterLiveness() to MachineBasicBlock. This uses analyzePhysReg() from r163694 to heuristically try and determine the liveness state of a physical register upon arrival at a particular instruction in a block. The search for liveness is clipped to a specific number of instructions around the target MachineInstr, in order to avoid degenerating into an O(N^2) algorithm. It tries to use various clues about how instructions around (both before and after) a given MachineInstr use that register, to determine its state at the MachineInstr. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163695 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/CodeGen/MachineBasicBlock.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/llvm/CodeGen/MachineBasicBlock.h') diff --git a/include/llvm/CodeGen/MachineBasicBlock.h b/include/llvm/CodeGen/MachineBasicBlock.h index 77ea4d03ea..97c39458d9 100644 --- a/include/llvm/CodeGen/MachineBasicBlock.h +++ b/include/llvm/CodeGen/MachineBasicBlock.h @@ -547,6 +547,28 @@ public: return findDebugLoc(MBBI.getInstrIterator()); } + /// Possible outcome of a register liveness query to computeRegisterLiveness() + enum LivenessQueryResult { + LQR_Live, ///< Register is known to be live. + LQR_OverlappingLive, ///< Register itself is not live, but some overlapping + ///< register is. + LQR_Dead, ///< Register is known to be dead. + LQR_Unknown ///< Register liveness not decidable from local + ///< neighborhood. + }; + + /// computeRegisterLiveness - Return whether (physical) register \c Reg + /// has been ined and not ed as of just before \c MI. + /// + /// Search is localised to a neighborhood of + /// \c Neighborhood instructions before (searching for defs or kills) and + /// Neighborhood instructions after (searching just for defs) MI. + /// + /// \c Reg must be a physical register. + LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI, + unsigned Reg, MachineInstr *MI, + unsigned Neighborhood=10); + // Debugging methods. void dump() const; void print(raw_ostream &OS, SlotIndexes* = 0) const; -- cgit v1.2.3-70-g09d2