[LLVMdev] Some questions about live intervals

[Evan Cheng]

Thanks. One question though. Should getMBBFromIndex() assert if given  
an index out of the range or simply returns a NULL pointer? I would  
think the later makes it a bit more friendly.

Evan

On Feb 8, 2008, at 8:59 AM, Roman Levenstein wrote:

> Hi Evan,
>
> Here is a patch for the LiveIntervalAnalysis that we discussed.
>
> --- Evan Cheng <evan.cheng at apple.com> schrieb:
>>> 1) What is the easiest way to understand which MBB a given
>> instruction index belongs to? All the required information is
>> available in the
>>> MBB2IdxMap of the LiveIntervalAnalysis class. Would it be useful
>> to add  a small function getMBBFromIndex() to this class?
>>
>> Sure there is a reverse map (actually just a vector) Idx2MBBMap.
>> Justadd a query.
>
> Done. Please find a patch attached to this mail.
>
>>> As for (1) and (2), I could implement and provide patches for it,
>>> if you think this is desirable.
>>
>> Yes, thanks.
>
> Here you are!
>
> -Roman
>
>
>      Lesen Sie Ihre E-Mails auf dem Handy.
> www.yahoo.de/goIndex: lib/CodeGen/LiveIntervalAnalysis.cpp
> ===================================================================
> --- lib/CodeGen/LiveIntervalAnalysis.cpp	(revision 46884)
> +++ lib/CodeGen/LiveIntervalAnalysis.cpp	(working copy)
> @@ -79,22 +79,7 @@
>     delete ClonedMIs[i];
> }
>
> -namespace llvm {
> -  inline bool operator<(unsigned V, const IdxMBBPair &IM) {
> -    return V < IM.first;
> -  }
>
> -  inline bool operator<(const IdxMBBPair &IM, unsigned V) {
> -    return IM.first < V;
> -  }
> -
> -  struct Idx2MBBCompare {
> -    bool operator()(const IdxMBBPair &LHS, const IdxMBBPair &RHS)  
> const {
> -      return LHS.first < RHS.first;
> -    }
> -  };
> -}
> -
> Index: include/llvm/CodeGen/LiveIntervalAnalysis.h
> ===================================================================
> --- include/llvm/CodeGen/LiveIntervalAnalysis.h	(revision 46884)
> +++ include/llvm/CodeGen/LiveIntervalAnalysis.h	(working copy)
> @@ -40,6 +40,20 @@
>   class VirtRegMap;
>   typedef std::pair<unsigned, MachineBasicBlock*> IdxMBBPair;
>
> +  inline bool operator<(unsigned V, const IdxMBBPair &IM) {
> +    return V < IM.first;
> +  }
> +
> +  inline bool operator<(const IdxMBBPair &IM, unsigned V) {
> +    return IM.first < V;
> +  }
> +
> +  struct Idx2MBBCompare {
> +    bool operator()(const IdxMBBPair &LHS, const IdxMBBPair &RHS)  
> const {
> +      return LHS.first < RHS.first;
> +    }
> +  };
> +
>   class LiveIntervals : public MachineFunctionPass {
>     MachineFunction* mf_;
>     const TargetMachine* tm_;
> @@ -153,6 +167,23 @@
>       return MBB2IdxMap[MBBNo].second;
>     }
>
> +    /// getMBBFromIndex - given an index in any instruction of an
> +    /// MBB return a pointer the MBB
> +    MachineBasicBlock* getMBBFromIndex(unsigned index) const {
> +      std::vector<IdxMBBPair>::const_iterator I =
> +	    std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), index);
> +
> +      // Take previous pair
> +      std::vector<IdxMBBPair>::const_iterator J =
> +	  ((I != Idx2MBBMap.end() && I->first > index) ||
> +	   (I == Idx2MBBMap.end() && Idx2MBBMap.size()>0)) ? (I-1): I;
> +
> +      assert(J != Idx2MBBMap.end() && J->first < index+1 &&
> +	     index < getMBBEndIdx(J->second) &&
> +	     "index does not correspond to an MBB");
> +      return J->second;
> +    }
> +
>     /// getInstructionIndex - returns the base index of instr
>     unsigned getInstructionIndex(MachineInstr* instr) const {
>       Mi2IndexMap::const_iterator it = mi2iMap_.find(instr);
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