From a368b89f2842530d07c0ac8e3b533882e165f197 Mon Sep 17 00:00:00 2001 From: Nadav Rotem Date: Tue, 30 Oct 2012 22:06:26 +0000 Subject: [PATCH] Add documentation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167055 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Vectorize/LoopVectorize.cpp | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index 9e05cacbbe9..431a8478a03 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -749,16 +749,21 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) { } +/// This function returns the identity element (or neutral element) for +/// the operation K. static unsigned getReductionIdentity(LoopVectorizationLegality::ReductionKind K) { switch (K) { case LoopVectorizationLegality::IntegerXor: case LoopVectorizationLegality::IntegerAdd: case LoopVectorizationLegality::IntegerOr: + // Adding, Xoring, Oring zero to a number does not change it. return 0; case LoopVectorizationLegality::IntegerMult: + // Multiplying a number by 1 does not change it. return 1; case LoopVectorizationLegality::IntegerAnd: + // AND-ing a number with an all-1 value does not change it. return -1; default: llvm_unreachable("Unknown reduction kind");