From 0b1a85f110c4ed50f7adf181490d9f6a1b4f55a5 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Wed, 1 Mar 2006 03:44:24 +0000 Subject: [PATCH] Pull shifts by a constant through multiplies (a form of reassociation), implementing Regression/CodeGen/X86/mul-shift-reassoc.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26440 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 27 ++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 5607e719d5a..ee8d22cb07e 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -726,6 +726,33 @@ SDOperand DAGCombiner::visitMUL(SDNode *N) { DAG.getConstant(Log2_64(-N1C->getSignExtended()), TLI.getShiftAmountTy()))); } + + // (mul (shl X, c1), c2) -> (mul X, c2 << c1) + if (N1C && N0.getOpcode() == ISD::SHL && + isa(N0.getOperand(1))) { + SDOperand C3 = DAG.getNode(ISD::SHL, VT, N1, N0.getOperand(1)); + return DAG.getNode(ISD::MUL, VT, N0.getOperand(0), C3); + } + + // Change (mul (shl X, C), Y) -> (shl (mul X, Y), C) when the shift has one + // use. + { + SDOperand Sh(0,0), Y(0,0); + // Check for both (mul (shl X, C), Y) and (mul Y, (shl X, C)). + if (N0.getOpcode() == ISD::SHL && isa(N0.getOperand(1)) && + N0.Val->hasOneUse()) { + Sh = N0; Y = N1; + } else if (N1.getOpcode() == ISD::SHL && + isa(N1.getOperand(1)) && N1.Val->hasOneUse()) { + Sh = N1; Y = N0; + } + if (Sh.Val) { + SDOperand Mul = DAG.getNode(ISD::MUL, VT, Sh.getOperand(0), Y); + return DAG.getNode(ISD::SHL, VT, Mul, Sh.getOperand(1)); + } + } + + // reassociate mul SDOperand RMUL = ReassociateOps(ISD::MUL, N0, N1); if (RMUL.Val != 0) -- 2.34.1