From 56ce9c4e78a6a8db5ec651f48a4acb8cf0d16c07 Mon Sep 17 00:00:00 2001 From: Andrea Di Biagio Date: Fri, 27 Sep 2013 11:37:05 +0000 Subject: Re-apply the change from r191393 with fix for pr17380. This change fixes the problem reported in pr17380 and re-add the dagcombine transformation ensuring that the value types are always legal if the transformation is triggered after Legalization took place. Added the test case from pr17380. llvm-svn: 191509 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'llvm/lib/CodeGen/SelectionDAG') diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index d5f3e9c53e2..f9458925885 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -3748,6 +3748,26 @@ SDValue DAGCombiner::visitSHL(SDNode *N) { } } + // fold (shl (zext (srl x, C)), C) -> (zext (shl (srl x, C), C)) + // Only fold this if the inner zext has no other uses to avoid increasing + // the total number of instructions. + if (N1C && N0.getOpcode() == ISD::ZERO_EXTEND && N0.hasOneUse() && + N0.getOperand(0).getOpcode() == ISD::SRL && + isa(N0.getOperand(0)->getOperand(1))) { + uint64_t c1 = + cast(N0.getOperand(0)->getOperand(1))->getZExtValue(); + if (c1 < VT.getSizeInBits()) { + uint64_t c2 = N1C->getZExtValue(); + if (c1 == c2) { + SDValue NewOp0 = N0.getOperand(0); + EVT CountVT = NewOp0.getOperand(1).getValueType(); + SDValue NewSHL = DAG.getNode(ISD::SHL, SDLoc(N), NewOp0.getValueType(), + NewOp0, DAG.getConstant(c2, CountVT)); + return DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N0), VT, NewSHL); + } + } + } + // fold (shl (srl x, c1), c2) -> (and (shl x, (sub c2, c1), MASK) or // (and (srl x, (sub c1, c2), MASK) // Only fold this if the inner shift has no other uses -- if it does, folding -- cgit v1.2.3