Fix typo in comment. (#3163)
diff --git a/source/opt/basic_block.h b/source/opt/basic_block.h
index 0bab337..6741a50 100644
--- a/source/opt/basic_block.h
+++ b/source/opt/basic_block.h
@@ -214,7 +214,7 @@
void KillAllInsts(bool killLabel);
// Splits this basic block into two. Returns a new basic block with label
- // |labelId| containing the instructions from |iter| onwards. Instructions
+ // |label_id| containing the instructions from |iter| onwards. Instructions
// prior to |iter| remain in this basic block. The new block will be added
// to the function immediately after the original block.
BasicBlock* SplitBasicBlock(IRContext* context, uint32_t label_id,
