049f179606
- extract KnownFPClass for future use inside of GISelKnownBits --------- Co-authored-by: Matt Arsenault <arsenm2@gmail.com>
95 lines
3.1 KiB
C++
95 lines
3.1 KiB
C++
//===- llvm/Support/KnownFPClass.h - Stores known fplcass -------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains a class for representing known fpclasses used by
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// computeKnownFPClass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/KnownFPClass.h"
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#include "llvm/Support/ErrorHandling.h"
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using namespace llvm;
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/// Return true if it's possible to assume IEEE treatment of input denormals in
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/// \p F for \p Val.
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static bool inputDenormalIsIEEE(DenormalMode Mode) {
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return Mode.Input == DenormalMode::IEEE;
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}
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static bool inputDenormalIsIEEEOrPosZero(DenormalMode Mode) {
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return Mode.Input == DenormalMode::IEEE ||
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Mode.Input == DenormalMode::PositiveZero;
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}
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bool KnownFPClass::isKnownNeverLogicalZero(DenormalMode Mode) const {
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return isKnownNeverZero() &&
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(isKnownNeverSubnormal() || inputDenormalIsIEEE(Mode));
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}
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bool KnownFPClass::isKnownNeverLogicalNegZero(DenormalMode Mode) const {
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return isKnownNeverNegZero() &&
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(isKnownNeverNegSubnormal() || inputDenormalIsIEEEOrPosZero(Mode));
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}
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bool KnownFPClass::isKnownNeverLogicalPosZero(DenormalMode Mode) const {
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if (!isKnownNeverPosZero())
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return false;
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// If we know there are no denormals, nothing can be flushed to zero.
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if (isKnownNeverSubnormal())
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return true;
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switch (Mode.Input) {
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case DenormalMode::IEEE:
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return true;
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case DenormalMode::PreserveSign:
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// Negative subnormal won't flush to +0
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return isKnownNeverPosSubnormal();
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case DenormalMode::PositiveZero:
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default:
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// Both positive and negative subnormal could flush to +0
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return false;
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}
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llvm_unreachable("covered switch over denormal mode");
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}
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void KnownFPClass::propagateDenormal(const KnownFPClass &Src,
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DenormalMode Mode) {
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KnownFPClasses = Src.KnownFPClasses;
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// If we aren't assuming the source can't be a zero, we don't have to check if
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// a denormal input could be flushed.
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if (!Src.isKnownNeverPosZero() && !Src.isKnownNeverNegZero())
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return;
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// If we know the input can't be a denormal, it can't be flushed to 0.
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if (Src.isKnownNeverSubnormal())
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return;
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if (!Src.isKnownNeverPosSubnormal() && Mode != DenormalMode::getIEEE())
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KnownFPClasses |= fcPosZero;
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if (!Src.isKnownNeverNegSubnormal() && Mode != DenormalMode::getIEEE()) {
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if (Mode != DenormalMode::getPositiveZero())
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KnownFPClasses |= fcNegZero;
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if (Mode.Input == DenormalMode::PositiveZero ||
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Mode.Output == DenormalMode::PositiveZero ||
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Mode.Input == DenormalMode::Dynamic ||
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Mode.Output == DenormalMode::Dynamic)
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KnownFPClasses |= fcPosZero;
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}
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}
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void KnownFPClass::propagateCanonicalizingSrc(const KnownFPClass &Src,
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DenormalMode Mode) {
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propagateDenormal(Src, Mode);
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propagateNaN(Src, /*PreserveSign=*/true);
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}
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