diff options
Diffstat (limited to 'include/llvm/CodeGen/LiveVariables.h')
| -rw-r--r-- | include/llvm/CodeGen/LiveVariables.h | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h index f6bc83162e..346fd9661d 100644 --- a/include/llvm/CodeGen/LiveVariables.h +++ b/include/llvm/CodeGen/LiveVariables.h @@ -51,13 +51,16 @@ public: /// 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. /// - /// 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. + /// 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 + /// 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, |