Merge pull request #84576 from tbkka/tbkka-revert-floatingpointdescription

Revert "Merge pull request #82750 from tbkka/tbkka-swift-floatingpointtostring"

Author: tbkka

Runtimes/Core/core/CMakeLists.txt

@@ -80,7 +80,6 @@ add_library(swiftCore
   FlatMap.swift
   Flatten.swift
   FloatingPoint.swift
-  FloatingPointToString.swift
   Hashable.swift
   AnyHashable.swift # ORDER DEPENDENCY
   Hasher.swift

Runtimes/Core/runtime/CMakeLists.txt

@@ -52,6 +52,7 @@ add_library(swiftRuntime OBJECT
     RefCount.cpp
     ReflectionMirror.cpp
     RuntimeInvocationsTracking.cpp
+    SwiftDtoa.cpp
     SwiftTLSContext.cpp
     ThreadingError.cpp
     Tracing.cpp

include/swift/Runtime/SwiftDtoa.h

@@ -0,0 +1,302 @@
+//===--- SwiftDtoa.h ---------------------------------------------*- c -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2018, 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===---------------------------------------------------------------------===//
+//
+/// About SwiftDtoa
+/// ===============
+///
+/// SwiftDtoa is the C implementation that supports the `.description`
+/// and `.debugDescription` properties for the standard Swift
+/// floating-point types.  These functions produce the "optimal form"
+/// for the binary floating point value.  The optimal form is a
+/// decimal representation that satisfies the following properties:
+///
+/// 1. Accurate.  Parsing the value back to a binary floating-point
+///    value of the same precision will exactly yield the original
+///    value.  For example, `Double(d.description) == d` for all `Double`
+///    values `d` (except for NaN values, of course).
+///
+/// 2. Short.  Of all accurate results, the returned value will
+///    contain the minimum number of significant digits.  Note that
+///    this is not quite the same as C++ `to_chars` which promises the
+///    minimal number of characters.
+///
+/// 3. Close.  Of all accurate, short results, the value printed will
+///    be the one that is closest to the exact binary floating-point
+///    value.
+///
+/// The optimal form is the ideal textual form for use in JSON and
+/// similar interchange formats because it is accurate, compact, and
+/// can be generated very quickly.  It is also ideal for logging and
+/// debugging use; the accuracy guarantees that the result can be
+/// cut-and-pasted to obtain the exact original value, and the
+/// shortness property eliminates unnecessary digits that can be
+/// confusing to readers.
+///
+/// Algorithms that produce such output have been known since at least
+/// 1990, when Steele and White published their Dragon4 algorithm.
+/// However, the earliest algorithms required high-precision
+/// arithmetic which limited their use.  Starting in 2010 with the
+/// publication of Grisu3, there has been a surge of interest and
+/// there are now a number of algorithms that can produce optimal
+/// forms very quickly.  This particular implementation is loosely
+/// based on Grisu2 but incorporates concepts from Errol and Ryu that
+/// make it significantly faster and ensure accuracy in all cases.
+///
+/// About SwiftDtoa v1
+/// ------------------
+///
+/// The first version of SwiftDtoa was committed to the Swift runtime
+/// in 2018.  It supported Swift's Float, Double, and Float80 formats.
+///
+/// About SwiftDtoa v1a
+/// -------------------
+///
+/// Version 1a of SwiftDtoa added support for Float16.
+///
+/// About SwiftDtoa v2
+/// ------------------
+///
+/// Version 2 of SwiftDtoa is a major overhaul with a number of
+/// algorithmic improvements to make it faster (especially for Float16
+/// and Float80), smaller, and more portable (the code only requires
+/// C99 and makes no use of C or C++ floating-point facilities).  It
+/// also includes experimental support for IEEE 754 quad-precision
+/// binary128 format, which is not currently supported by Swift.
+//
+//===---------------------------------------------------------------------===//
+
+#ifndef SWIFT_DTOA_H
+#define SWIFT_DTOA_H
+
+#define __STDC_WANT_IEC_60559_TYPES_EXT__ // FLT16_MAX
+#include <float.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+//
+// IEEE 754 Binary16 support (also known as "half-precision")
+//
+
+// Enable this by default.
+// Force disable: -DSWIFT_DTOA_BINARY16_SUPPORT=0
+#ifndef SWIFT_DTOA_BINARY16_SUPPORT
+ #define SWIFT_DTOA_BINARY16_SUPPORT 1
+#endif
+
+/// Does this platform support needs to pass _Float16 as a float in
+/// C function?
+#ifndef SWIFT_DTOA_PASS_FLOAT16_AS_FLOAT
+// Windows does not define FLT16_MAX even though it supports _Float16 as argument.
+# if (!defined(FLT16_MAX) || defined(__wasm__)) && !defined(_WIN32)
+#  define SWIFT_DTOA_PASS_FLOAT16_AS_FLOAT 1
+# else
+#  define SWIFT_DTOA_PASS_FLOAT16_AS_FLOAT 0
+# endif
+#endif
+
+//
+// IEEE 754 Binary32 support (also known as "single-precision")
+//
+
+// Does "float" on this system use binary32 format?
+// (Almost all modern systems do this.)
+#if (FLT_RADIX == 2) && (FLT_MANT_DIG == 24) && (FLT_MIN_EXP == -125) && (FLT_MAX_EXP == 128)
+  #define FLOAT_IS_BINARY32 1
+#else
+  #undef FLOAT_IS_BINARY32
+#endif
+
+// We can format binary32 values even if the local C environment
+// does not support it.  But `float` == binary32 almost everywhere,
+// so we enable it by default.
+// Force disable: -DSWIFT_DTOA_BINARY32_SUPPORT=0
+#ifndef SWIFT_DTOA_BINARY32_SUPPORT
+ #define SWIFT_DTOA_BINARY32_SUPPORT 1
+#endif
+
+//
+// IEEE 754 Binary64 support (also known as "double-precision")
+//
+
+// Does "double" on this system use binary64 format?
+// (Almost all modern systems do this.)
+#if (FLT_RADIX == 2) && (DBL_MANT_DIG == 53) && (DBL_MIN_EXP == -1021) && (DBL_MAX_EXP == 1024)
+  #define DOUBLE_IS_BINARY64 1
+#else
+  #undef DOUBLE_IS_BINARY64
+#endif
+
+// Does "long double" on this system use binary64 format?
+// (Windows, for example.)
+#if (FLT_RADIX == 2) && (LDBL_MANT_DIG == 53) && (LDBL_MIN_EXP == -1021) && (LDBL_MAX_EXP == 1024)
+  #define LONG_DOUBLE_IS_BINARY64 1
+#else
+  #undef LONG_DOUBLE_IS_BINARY64
+#endif
+
+// We can format binary64 values even if the local C environment
+// does not support it.  But `double` == binary64 almost everywhere,
+// so we enable it by default.
+// Force disable: -DSWIFT_DTOA_BINARY64_SUPPORT=0
+#ifndef SWIFT_DTOA_BINARY64_SUPPORT
+ #define SWIFT_DTOA_BINARY64_SUPPORT 1
+#endif
+
+//
+// Intel x87 Float80 support
+//
+
+// Is "long double" on this system the same as Float80?
+// (macOS, Linux, and FreeBSD when running on x86 or x86_64 processors.)
+#if (FLT_RADIX == 2) && (LDBL_MANT_DIG == 64) && (LDBL_MIN_EXP == -16381) && (LDBL_MAX_EXP == 16384)
+ #define LONG_DOUBLE_IS_FLOAT80 1
+#else
+ #undef LONG_DOUBLE_IS_FLOAT80
+#endif
+
+// We can format float80 values even if the local C environment
+// does not support it.  However, by default, we only enable it for
+// environments where float80 == long double.
+// Force enable: -DSWIFT_DTOA_FLOAT80_SUPPORT=1
+// Force disable: -DSWIFT_DTOA_FLOAT80_SUPPORT=0
+#ifndef SWIFT_DTOA_FLOAT80_SUPPORT
+ #if LONG_DOUBLE_IS_FLOAT80
+  #define SWIFT_DTOA_FLOAT80_SUPPORT 1
+ #endif
+#endif
+
+//
+// IEEE 754 Binary128 support
+//
+
+// Is "long double" on this system the same as Binary128?
+// (Android on LP64 hardware.)
+#if (FLT_RADIX == 2) && (LDBL_MANT_DIG == 113) && (LDBL_MIN_EXP == -16381) && (LDBL_MAX_EXP == 16384)
+ #define LONG_DOUBLE_IS_BINARY128 1
+#else
+ #undef LONG_DOUBLE_IS_BINARY128
+#endif
+
+// We can format binary128 values even if the local C environment
+// does not support it.  However, by default, we only enable it for
+// environments where binary128 == long double.
+// Force enable: -DSWIFT_DTOA_BINARY128_SUPPORT=1
+// Force disable: -DSWIFT_DTOA_BINARY128_SUPPORT=0
+#ifndef SWIFT_DTOA_BINARY128_SUPPORT
+ #if LONG_DOUBLE_IS_BINARY128
+  #define SWIFT_DTOA_BINARY128_SUPPORT 1
+ #endif
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Format a floating point value as an ASCII string
+//
+// Input:
+// * `d` is the number to be formatted
+// * `dest` is a buffer of length `length`
+//
+// Output:
+// * Return value is the length of the string placed into `dest`
+//   or zero if the buffer is too small.
+// * For infinity, it copies "inf" or "-inf".
+// * For NaN, it outputs a Swift-style detailed dump, including
+//   sign, signaling/quiet, and payload (if any).  Typical output:
+//   "nan", "-nan", "-snan(0x1234)".
+// * For zero, it outputs "0.0" or "-0.0" depending on the sign.
+// * The destination buffer is always null-terminated (even on error)
+//   unless the length is zero.
+//
+// Note: If you want to customize the output for Infinity, zero, or
+// Nan, you can easily write a wrapper function that uses `fpclassify`
+// to identify those cases and only calls through to these functions
+// for normal and subnormal values.
+//
+// Guarantees:
+//
+// * Accurate. If you parse the result back to the same floating-point
+//   format via an accurate algorithm (such as Clinger's algorithm),
+//   the resulting value will be _exactly_ equal to the original value.
+//   On most systems, this implies that using `strtod` to parse the
+//   output of `swift_dtoa_optimal_double` will yield exactly the
+//   original value.
+//
+// * Short. No other accurate result will have fewer digits.
+//
+// * Close. If there are multiple possible decimal forms that are
+//   both accurate and short, the form computed here will be
+//   closest to the original binary value.
+//
+// Naming: The `_p` forms take a `const void *` pointing to the value
+// in memory.  These forms do not require any support from the local C
+// environment.  In particular, they should work correctly even on
+// systems with no floating-point support.  Forms ending in a C
+// floating-point type (e.g., "_float", "_double") are identical but
+// take the corresponding argument type.  These forms obviously
+// require the C environment to support passing floating-point types as
+// function arguments.
+
+#if SWIFT_DTOA_BINARY16_SUPPORT
+size_t swift_dtoa_optimal_binary16_p(const void *, char *dest, size_t length);
+#if !SWIFT_DTOA_PASS_FLOAT16_AS_FLOAT
+// If `_Float16` is defined, provide this convenience wrapper.
+size_t swift_dtoa_optimal_binary16(_Float16, char *dest, size_t length);
+#endif
+#endif
+
+#if SWIFT_DTOA_BINARY32_SUPPORT
+size_t swift_dtoa_optimal_binary32_p(const void *, char *dest, size_t length);
+#if FLOAT_IS_BINARY32
+// If `float` happens to be binary32, define the convenience wrapper.
+size_t swift_dtoa_optimal_float(float, char *dest, size_t length);
+#endif
+#endif
+
+#if SWIFT_DTOA_BINARY64_SUPPORT
+size_t swift_dtoa_optimal_binary64_p(const void *, char *dest, size_t length);
+#if DOUBLE_IS_BINARY64
+// If `double` happens to be binary64, define the convenience wrapper.
+size_t swift_dtoa_optimal_double(double, char *dest, size_t length);
+#endif
+#if LONG_DOUBLE_IS_BINARY64
+// If `long double` happens to be binary64, define the convenience wrapper.
+size_t swift_dtoa_optimal_long_double(long double, char *dest, size_t length);
+#endif
+#endif
+
+#if SWIFT_DTOA_FLOAT80_SUPPORT
+// Universal entry point works on all platforms, regardless of
+// whether the local system has direct support for float80
+size_t swift_dtoa_optimal_float80_p(const void *, char *dest, size_t length);
+#if LONG_DOUBLE_IS_FLOAT80
+// If 'long double' happens to be float80, define a convenience wrapper.
+size_t swift_dtoa_optimal_long_double(long double, char *dest, size_t length);
+#endif
+#endif
+
+#if SWIFT_DTOA_BINARY128_SUPPORT
+// Universal entry point works on all platforms, regardless of
+// whether the local system has direct support for float80
+size_t swift_dtoa_optimal_binary128_p(const void *, char *dest, size_t length);
+#if LONG_DOUBLE_IS_BINARY128
+// If 'long double' happens to be binary128, define a convenience wrapper.
+size_t swift_dtoa_optimal_long_double(long double, char *dest, size_t length);
+#endif
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+#endif

stdlib/public/core/CMakeLists.txt

@@ -261,7 +261,6 @@ split_embedded_sources(
 
     NORMAL AtomicInt.swift.gyb
   EMBEDDED FloatingPointParsing.swift.gyb
-  EMBEDDED FloatingPointToString.swift
   EMBEDDED FloatingPointTypes.swift.gyb
   EMBEDDED IntegerTypes.swift.gyb
   EMBEDDED LegacyInt128.swift.gyb