From 4a44c8df1984ebcb253dda283bd2c117cbbb1929 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 18 Apr 2005 04:30:45 +0000 Subject: [PATCH] Another minor simplification: handle setcc (zero_extend x), c -> setcc(x, c') git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21318 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 45 +++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index a52289fb387..fbadd6323c9 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -406,6 +406,51 @@ SDOperand SelectionDAG::getSetCC(ISD::CondCode Cond, MVT::ValueType VT, case ISD::SETGE: return getConstant((int64_t)C1 >= (int64_t)C2, VT); } } else { + // If the LHS is a ZERO_EXTEND and if this is an ==/!= comparison, perform + // the comparison on the input. + if (N1.getOpcode() == ISD::ZERO_EXTEND) { + unsigned InSize = MVT::getSizeInBits(N1.getOperand(0).getValueType()); + + // If the comparison constant has bits in the upper part, the + // zero-extended value could never match. + if (C2 & (~0ULL << InSize)) { + unsigned VSize = MVT::getSizeInBits(N1.getValueType()); + switch (Cond) { + case ISD::SETUGT: + case ISD::SETUGE: + case ISD::SETEQ: return getConstant(0, VT); + case ISD::SETULT: + case ISD::SETULE: + case ISD::SETNE: return getConstant(1, VT); + case ISD::SETGT: + case ISD::SETGE: + // True if the sign bit of C2 is set. + return getConstant((C2 & (1ULL << VSize)) != 0, VT); + case ISD::SETLT: + case ISD::SETLE: + // True if the sign bit of C2 isn't set. + return getConstant((C2 & (1ULL << VSize)) == 0, VT); + default: + break; + } + } + + // Otherwise, we can perform the comparison with the low bits. + switch (Cond) { + case ISD::SETEQ: + case ISD::SETNE: + case ISD::SETUGT: + case ISD::SETUGE: + case ISD::SETULT: + case ISD::SETULE: + return getSetCC(Cond, VT, N1.getOperand(0), + getConstant(C2, N1.getOperand(0).getValueType())); + default: + break; // todo, be more careful with signed comparisons + } + } + + uint64_t MinVal, MaxVal; unsigned OperandBitSize = MVT::getSizeInBits(N2C->getValueType(0)); if (ISD::isSignedIntSetCC(Cond)) { -- 2.34.1