[llvm-commits] [llvm] r59145 - /llvm/trunk/include/llvm/CodeGen/LiveVariables.h

[Evan Cheng]

On Nov 12, 2008, at 9:02 AM, Dan Gohman wrote:

> Author: djg
> Date: Wed Nov 12 11:02:24 2008
> New Revision: 59145
>
> URL: http://llvm.org/viewvc/llvm-project?rev=59145&view=rev
> Log:
> Update VarInfo's comments to reflect the current code. LiveVar
> no longer records a unique defining instruction,


> and virtual
> registers may have multiple kills while still being defined
> and killed in the same block.

Are you sure?

Evan

>
>
> Modified:
>    llvm/trunk/include/llvm/CodeGen/LiveVariables.h
>
> Modified: llvm/trunk/include/llvm/CodeGen/LiveVariables.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LiveVariables.h?rev=59145&r1=59144&r2=59145&view=diff
>
> =
> =
> =
> =
> =
> =
> =
> =
> ======================================================================
> --- llvm/trunk/include/llvm/CodeGen/LiveVariables.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/LiveVariables.h Wed Nov 12  
> 11:02:24 2008
> @@ -47,20 +47,17 @@
>
>   /// VarInfo - This represents the regions where a virtual register  
> is live in
>   /// the program.  We represent this with three different pieces of
> -  /// information: the instruction that uniquely defines the value,  
> the set of
> -  /// blocks the instruction is live into and live out of, and the  
> set of
> -  /// non-phi instructions that are the last users of the value.
> +  /// information: the set of blocks in which the instruction is live
> +  /// throughout, the set of blocks in which the instruction is  
> actually used,
> +  /// and the set of non-phi instructions that are the last users  
> of the value.
>   ///
> -  /// In the common case where a value is defined and killed in the  
> same block,
> -  /// There is one killing instruction, and  AliveBlocks is empty.
> -  ///
> -  /// Otherwise, the value is live out of the block.  If the value  
> is live
> -  /// across any blocks, these blocks are listed in AliveBlocks.   
> Blocks where
> -  /// the liveness range ends are not included in AliveBlocks,  
> instead being
> -  /// captured by the Kills set.  In these blocks, the value is  
> live into the
> -  /// block (unless the value is defined and killed in the same  
> block) and lives
> -  /// until the specified instruction.  Note that there cannot ever  
> be a value
> -  /// whose Kills set contains two instructions from the same basic  
> block.
> +  /// If the value is live throughout any blocks, these blocks are  
> listed in
> +  /// AliveBlocks.  Blocks where the liveness range ends are not  
> included in
> +  /// AliveBlocks, instead being captured by the Kills set.  In  
> these blocks,
> +  /// the value is live into the block (unless the value is defined  
> and killed
> +  /// in the same block) and lives until the specified  
> instruction.  Note that
> +  /// there cannot ever be a value whose Kills set contains two  
> instructions
> +  /// from the same basic block.
>   ///
>   /// PHI nodes complicate things a bit.  If a PHI node is the last  
> user of a
>   /// value in one of its predecessor blocks, it is not listed in  
> the kills set,
> @@ -72,13 +69,13 @@
>   /// included). This is sensical because the value must be live to  
> the end of
>   /// the block, but is not live in any successor blocks.
>   struct VarInfo {
> -    /// AliveBlocks - Set of blocks of which this value is alive  
> completely
> +    /// AliveBlocks - Set of blocks in which this value is alive  
> completely
>     /// through.  This is a bit set which uses the basic block  
> number as an
>     /// index.
>     ///
>     BitVector AliveBlocks;
>
> -    /// UsedBlocks - Set of blocks of which this value is actually  
> used. This
> +    /// UsedBlocks - Set of blocks in which this value is actually  
> used. This
>     /// is a bit set which uses the basic block number as an index.
>     BitVector UsedBlocks;
>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits