From 4f3985a860d66fa7b3431668f03b8490b1eeff79 Mon Sep 17 00:00:00 2001 From: Ramkumar Ramachandra Date: Tue, 15 Oct 2024 16:06:05 +0100 Subject: [PATCH] ValueTracking: clarify isNotCrossLaneOperation (NFC) Clarify the distinction between lanewise operations, and operations that do not cross vector lanes, with an example, in the header comment. --- llvm/include/llvm/Analysis/ValueTracking.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h index 0c6ebf87b2923..2b0377903ac8e 100644 --- a/llvm/include/llvm/Analysis/ValueTracking.h +++ b/llvm/include/llvm/Analysis/ValueTracking.h @@ -791,7 +791,12 @@ bool onlyUsedByLifetimeMarkers(const Value *V); /// droppable instructions. bool onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V); -/// Return true if the instruction doesn't potentially cross vector lanes. +/// Return true if the instruction doesn't potentially cross vector lanes. This +/// condition is weaker than checking that the instruction is lanewise: lanewise +/// means that the same operation is splatted across all lanes, but we also +/// include the case where there is a different operation on each lane, as long +/// as the operation only uses data from that lane. An example of an operation +/// that is not lanewise, but doesn't cross vector lanes is insertelement. bool isNotCrossLaneOperation(const Instruction *I); /// Return true if the instruction does not have any effects besides