From 4218443a430ae477b64b8edf2a6fd0d88cfe9344 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 29 Dec 2007 08:37:08 +0000 Subject: Fold comparisons against a constant nan, and optimize ORD/UNORD comparisons with a constant. This allows us to compile isnan to: _foo: fcmpu cr7, f1, f1 mfcr r2 rlwinm r3, r2, 0, 31, 31 blr instead of: LCPI1_0: ; float .space 4 _foo: lis r2, ha16(LCPI1_0) lfs f0, lo16(LCPI1_0)(r2) fcmpu cr7, f1, f0 mfcr r2 rlwinm r3, r2, 0, 31, 31 blr git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45405 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/TargetLowering.cpp | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'lib/CodeGen') diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp index eb08bba..ad33273 100644 --- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -1280,6 +1280,28 @@ TargetLowering::SimplifySetCC(MVT::ValueType VT, SDOperand N0, SDOperand N1, // Constant fold or commute setcc. SDOperand O = DAG.FoldSetCC(VT, N0, N1, Cond); if (O.Val) return O; + } else if (ConstantFPSDNode *CFP = dyn_cast(N1.Val)) { + // If the RHS of an FP comparison is a constant, simplify it away in + // some cases. + if (CFP->getValueAPF().isNaN()) { + // If an operand is known to be a nan, we can fold it. + switch (ISD::getUnorderedFlavor(Cond)) { + default: assert(0 && "Unknown flavor!"); + case 0: // Known false. + return DAG.getConstant(0, VT); + case 1: // Known true. + return DAG.getConstant(1, VT); + case 2: // undefind. + return DAG.getNode(ISD::UNDEF, VT); + } + } + + // Otherwise, we know the RHS is not a NaN. Simplify the node to drop the + // constant if knowing that the operand is non-nan is enough. We prefer to + // have SETO(x,x) instead of SETO(x, 0.0) because this avoids having to + // materialize 0.0. + if (Cond == ISD::SETO || Cond == ISD::SETUO) + return DAG.getSetCC(VT, N0, N0, Cond); } if (N0 == N1) { -- cgit v1.1