From e6c145e0548e3b3de6eab27e44e1504387cf6b53 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Fri, 25 Oct 2019 13:34:40 -0400 Subject: [DAGCombiner] widen zext of popcount based on target support zext (ctpop X) --> ctpop (zext X) This is a prerequisite step for canonicalizing in the other direction (narrow the popcount) in IR - PR43688: https://bugs.llvm.org/show_bug.cgi?id=43688 I'm not sure if any other targets are affected, but I found a missing fold for PPC, so added tests based on that. The reason we widen all the way to 64-bit in these tests is because the initial DAG looks something like this: t5: i8 = ctpop t4 t6: i32 = zero_extend t5 <-- created based on IR, but unused node? t7: i64 = zero_extend t5 Differential Revision: https://reviews.llvm.org/D69127 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'llvm/lib/CodeGen') diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index cdf8395046c..f00e332de9c 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -9921,6 +9921,18 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) { if (SDValue NewVSel = matchVSelectOpSizesWithSetCC(N)) return NewVSel; + // If the target does not support a pop-count in the narrow source type but + // does support it in the destination type, widen the pop-count to this type: + // zext (ctpop X) --> ctpop (zext X) + // TODO: Generalize this to handle starting from anyext. + if (N0.getOpcode() == ISD::CTPOP && N0.hasOneUse() && + !TLI.isOperationLegalOrCustom(ISD::CTPOP, N0.getValueType()) && + TLI.isOperationLegalOrCustom(ISD::CTPOP, VT)) { + SDLoc DL(N); + SDValue NewZext = DAG.getZExtOrTrunc(N0.getOperand(0), DL, VT); + return DAG.getNode(ISD::CTPOP, DL, VT, NewZext); + } + return SDValue(); } -- cgit v1.2.3