From 28865062c1ef60e47f0ac23a5ebc22eaf0d1b184 Mon Sep 17 00:00:00 2001 From: Bob Wilson Date: Thu, 13 Aug 2009 02:13:04 +0000 Subject: [PATCH] Add a comment to describe why vector shuffles are legalized to custom DAG nodes. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78884 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/ARM/ARMISelLowering.cpp | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp index 4074fc7f219..785a7ded6d3 100644 --- a/lib/Target/ARM/ARMISelLowering.cpp +++ b/lib/Target/ARM/ARMISelLowering.cpp @@ -2439,6 +2439,10 @@ static SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) { DebugLoc dl = Op.getDebugLoc(); EVT VT = Op.getValueType(); + // Convert shuffles that are directly supported on NEON to target-specific + // DAG nodes, instead of keeping them as shuffles and matching them again + // during code selection. This is more efficient and avoids the possibility + // of inconsistencies between legalization and selection. if (SVN->isSplat() && SVN->getSplatIndex() == 0) return DAG.getNode(ARMISD::VSPLAT0, dl, VT, SVN->getOperand(0)); if (isVREVMask(SVN, 64))