From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 21:33:14 +0200 Subject: Adding upstream version 115.7.0esr. Signed-off-by: Daniel Baumann --- mfbt/FloatingPoint.cpp | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 mfbt/FloatingPoint.cpp (limited to 'mfbt/FloatingPoint.cpp') diff --git a/mfbt/FloatingPoint.cpp b/mfbt/FloatingPoint.cpp new file mode 100644 index 0000000000..4d52ffaaf8 --- /dev/null +++ b/mfbt/FloatingPoint.cpp @@ -0,0 +1,41 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* Implementations of FloatingPoint functions */ + +#include "mozilla/FloatingPoint.h" + +#include // for FLT_MAX + +namespace mozilla { + +bool IsFloat32Representable(double aValue) { + // NaNs and infinities are representable. + if (!std::isfinite(aValue)) { + return true; + } + + // If it exceeds finite |float| range, casting to |double| is always undefined + // behavior per C++11 [conv.double]p1 last sentence. + if (Abs(aValue) > FLT_MAX) { + return false; + } + + // But if it's within finite range, then either it's 1) an exact value and so + // representable, or 2) it's "between two adjacent destination values" and + // safe to cast to "an implementation-defined choice of either of those + // values". + auto valueAsFloat = static_cast(aValue); + + // Per [conv.fpprom] this never changes value. + auto valueAsFloatAsDouble = static_cast(valueAsFloat); + + // Finally, in 1) exact representable value equals exact representable value, + // or 2) *changed* value does not equal original value, ergo unrepresentable. + return valueAsFloatAsDouble == aValue; +} + +} /* namespace mozilla */ -- cgit v1.2.3