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-
-TestFloat Release 2a Source Documentation
-
-John R. Hauser
-1998 December 16
-
-
--------------------------------------------------------------------------------
-Introduction
-
-TestFloat is a program for testing that a floating-point implementation
-conforms to the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
-All standard operations supported by the system can be tested, except for
-conversions to and from decimal. Any of the following machine formats can
-be tested: single precision, double precision, extended double precision,
-and/or quadruple precision. Testing extended double-precision or quadruple-
-precision formats requires a C compiler that supports 64-bit integer
-arithmetic.
-
-This document gives information needed for compiling and/or porting
-TestFloat.
-
-The source code for TestFloat is intended to be relatively machine-
-independent. TestFloat is written in C, and should be compilable using
-any ISO/ANSI C compiler. At the time of this writing, the program has
-been successfully compiled using the GNU C Compiler (`gcc') for several
-platforms. Because ISO/ANSI C does not provide access to some features
-of IEC/IEEE floating-point such as the exception flags, porting TestFloat
-unfortunately involves some machine-dependent coding.
-
-TestFloat depends on SoftFloat, which is a software implementation of
-floating-point that conforms to the IEC/IEEE Standard. SoftFloat is not
-included with the TestFloat sources. It can be obtained from the Web
-page `http://HTTP.CS.Berkeley.EDU/~jhauser/arithmetic/SoftFloat.html'.
-
-In addition to a program for testing a machine's floating-point, the
-TestFloat package includes a variant for testing SoftFloat called
-`testsoftfloat'. The sources for both programs are intermixed, and both are
-described here.
-
-The first release of TestFloat (Release 1) was called _FloatTest_. The old
-name has been obsolete for some time.
-
-
--------------------------------------------------------------------------------
-Limitations
-
-TestFloat as written requires an ISO/ANSI-style C compiler. No attempt has
-been made to accommodate compilers that are not ISO-conformant. Older ``K&R-
-style'' compilers are not adequate for compiling TestFloat. All testing I
-have done so far has been with the GNU C Compiler. Compilation with other
-compilers should be possible but has not been tested.
-
-The TestFloat sources assume that source code file names can be longer than
-8 characters. In order to compile under an MS-DOS-style system, many of the
-source files will need to be renamed, and the source and makefiles edited
-appropriately. Once compiled, the TestFloat program does not depend on the
-existence of long file names.
-
-The underlying machine is assumed to be binary with a word size that is a
-power of 2. Bytes are 8 bits. Testing of extended double-precision and
-quadruple-precision formats depends on the C compiler implementing a 64-bit
-integer type. If the largest integer type supported by the C compiler is
-32 bits, only single- and double-precision operations can be tested.
-
-
--------------------------------------------------------------------------------
-Contents
-
- Introduction
- Limitations
- Contents
- Legal Notice
- TestFloat Source Directory Structure
- Target-Independent Modules
- Target-Specific Modules
- Target-Specific Header Files
- processors/*.h
- testfloat/*/milieu.h
- Target-Specific Floating-Point Subroutines
- Steps to Creating the TestFloat Executables
- Improving the Random Number Generator
- Contact Information
-
-
-
--------------------------------------------------------------------------------
-Legal Notice
-
-TestFloat was written by John R. Hauser.
-
-THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE. Although reasonable effort
-has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
-TIMES RESULT IN INCORRECT BEHAVIOR. USE OF THIS SOFTWARE IS RESTRICTED TO
-PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
-AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.
-
-
--------------------------------------------------------------------------------
-TestFloat Source Directory Structure
-
-Because TestFloat is targeted to multiple platforms, its source code
-is slightly scattered between target-specific and target-independent
-directories and files. The directory structure is as follows:
-
- processors
- testfloat
- templates
- 386-Win32-gcc
- SPARC-Solaris-gcc
-
-The two topmost directories and their contents are:
-
- testfloat - Most of the source code needed for TestFloat.
- processors - Target-specific header files that are not specific to
- TestFloat.
-
-Within the `testfloat' directory are subdirectories for each of the
-targeted platforms. The TestFloat source code is distributed with targets
-`386-Win32-gcc' and `SPARC-Solaris-gcc' (and perhaps others) already
-prepared. These can be used as examples for porting to new targets. Source
-files that are not within these target-specific subdirectories are intended
-to be target-independent.
-
-The naming convention used for the target-specific directories is
-`<processor>-<executable-type>-<compiler>'. The names of the supplied
-target directories should be interpreted as follows:
-
- <processor>:
- 386 - Intel 386-compatible processor.
- SPARC - SPARC processor (as used by Sun machines).
- <executable-type>:
- Win32 - Microsoft Win32 executable.
- Solaris - Sun Solaris executable.
- <compiler>:
- gcc - GNU C Compiler.
-
-You do not need to maintain this convention if you do not want to.
-
-Alongside the supplied target-specific directories there is a `templates'
-directory containing a set of ``generic'' target-specific source files.
-A new target directory can be created by copying the `templates' directory
-and editing the files inside. (Complete instructions for porting TestFloat
-to a new target are in the section _Steps_to_Creating_the_TestFloat_
-_Executables_.) Note that the `templates' directory will not work as a
-target directory without some editing. To avoid confusion, it would be wise
-to refrain from editing the files inside `templates' directly.
-
-In addition to the distributed sources, TestFloat depends on the existence
-of an appropriately-compiled SoftFloat binary and the corresponding header
-file `softfloat.h'. SoftFloat is not included with the TestFloat sources.
-It can be obtained from the Web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
-arithmetic/SoftFloat.html'.
-
-As distributed, the makefiles for TestFloat assume the existence of three
-sibling directories:
-
- processors
- softfloat
- testfloat
-
-Only the `processors' and `testfloat' directories are included in the
-TestFloat package. The `softfloat' directory is assumed to contain a
-target-specific subdirectory within which the SoftFloat header file and
-compiled binary can be found. (See the source documentation accompanying
-SoftFloat.) The `processors' directory distributed with TestFloat is
-intended to be identical to that included with the SoftFloat source.
-
-These are the defaults, but other organizations of the sources are possible.
-The TestFloat makefiles and `milieu.h' files (see below) are easily edited
-to accommodate other arrangements.
-
-
--------------------------------------------------------------------------------
-Target-Independent Modules
-
-The TestFloat program is composed of a number of modules, some target-
-specific and some target-independent. The target-independent modules are as
-follows:
-
--- The `fail' module provides a common routine for writing an error message
- and aborting.
-
--- The `random' module generates random integer values.
-
--- The `writeHex' module defines routines for writing the various types in
- the hexadecimal form used by TestFloat.
-
--- The `testCases' module generates test cases for the various types.
-
--- The `testLoops' module contains various routines for exercising two
- implementations of a function and reporting any differences observed.
-
--- The `slowfloat' module provides the simple floating-point implementation
- used by `testsoftfloat' for comparing against SoftFloat. The heart
- of `slowfloat' is found in either `slowfloat-32' or `slowfloat-64',
- depending on whether the `BITS64' macro is defined.
-
--- The `systfloat' module gives a SoftFloat-like interface to the machine's
- floating-point.
-
--- The `testFunction' module implements `testfloat's main loop for testing a
- function for all of the relevant rounding modes and rounding precisions.
- (The `testsoftfloat' program contains its own version of this code.)
-
--- The `testfloat' and `testsoftfloat' modules are the main modules for the
- `testfloat' and `testsoftfloat' programs.
-
-Except possibly for `systfloat', these modules should not need to be
-modified.
-
-The `systfloat' module uses the floating-point operations of the C language
-to access a machine's floating-point. Unfortunately, some IEC/IEEE
-floating-point operations are not accessible within ISO/ANSI C. The
-following machine functions cannot be tested unless an alternate `systfloat'
-module is provided:
-
- <float>_to_int32 (rounded according to rounding mode)
- <float>_to_int64 (rounded according to rounding mode)
- <float>_round_to_int
- <float>_rem
- <float>_sqrt, except float64_sqrt
- <float>_eq_signaling
- <float>_le_quiet
- <float>_lt_quiet
-
-The `-list' option to `testfloat' will show the operations the program is
-prepared to test. The section _Target-Specific_Floating-Point_Subroutines_
-later in this document explains how to create a target-specific `systfloat'
-module to change the set of testable functions.
-
-
--------------------------------------------------------------------------------
-Target-Specific Modules
-
-No target-specific modules are needed for `testsoftfloat'.
-
-The `testfloat' program uses two target-specific modules:
-
--- The `systmodes' module defines functions for setting the modes
- controlling the system's floating-point, including the rounding mode and
- the rounding precision for extended double precision.
-
--- The `systflags' module provides a function for clearing and examining the
- system's floating-point exception flags.
-
-These modules must be supplied for each target. They can be implemented in
-any way desired, so long as all is reflected in the target's makefile. For
-the targets that come with the distributed source, each of these modules is
-implemented as a single assembly language or C language source file.
-
-
--------------------------------------------------------------------------------
-Target-Specific Header Files
-
-The purpose of the two target-specific header files is detailed below.
-In the following, the `*' symbol is used in place of the name of a specific
-target, such as `386-Win32-gcc' or `SPARC-Solaris-gcc', or in place of some
-other text as explained below.
-
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-processors/*.h
-
-The target-specific `processors' header file defines integer types
-of various sizes, and also defines certain C preprocessor macros that
-characterize the target. The two examples supplied are `386-gcc.h' and
-`SPARC-gcc.h'. The naming convention used for processor header files is
-`<processor>-<compiler>.h'. The `processors' header file used to compile
-TestFloat should be the same as that used to compile SoftFloat.
-
-If 64-bit integers are supported by the compiler, the macro name `BITS64'
-should be defined here along with the corresponding 64-bit integer
-types. In addition, the function-like macro `LIT64' must be defined for
-constructing 64-bit integer literals (constants). The `LIT64' macro is used
-consistently in the TestFloat code to annotate 64-bit literals.
-
-If an inlining attribute (such as an `inline' keyword) is provided by the
-compiler, the macro `INLINE' should be defined to the appropriate keyword.
-If not, `INLINE' can be set to the keyword `static'. The `INLINE' macro
-appears in the TestFloat source code before every function that should be
-inlined by the compiler.
-
-For maximum flexibility, the TestFloat source files do not include the
-`processors' header file directly; rather, this file is included by the
-target-specific `milieu.h' header, and `milieu.h' is included by the source
-files.
-
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-testfloat/*/milieu.h
-
-The `milieu.h' header file provides declarations that are needed to
-compile TestFloat. In particular, it is through this header file that
-the appropriate `processors' header is included to characterize the target
-processor. In addition, deviations from ISO/ANSI C by the compiler (such as
-names not properly declared in system header files) are corrected in this
-header if possible.
-
-If the preprocessor macro `BITS64' is defined in the `processors' header
-file but only the 32-bit version of SoftFloat is actually used, the `BITS64'
-macro should be undefined here after the `processors' header has defined it.
-
-If the C compiler implements the `long double' floating-point type of C
-as extended double precision, then `LONG_DOUBLE_IS_FLOATX80' should be
-defined here. Alternatively, if the C `long double' type is implemented as
-quadruple precision, `LONG_DOUBLE_IS_FLOAT128' should be defined. At most
-one of these macros should be defined. A C compiler is allowed to implement
-`long double' the same as `double', in which case neither of these macros
-should be defined.
-
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
-
--------------------------------------------------------------------------------
-Target-Specific Floating-Point Subroutines
-
-This section applies only to `testfloat' and not to `testsoftfloat'.
-
-By default, TestFloat tests a machine's floating-point by testing the
-floating-point operations of the C language. Unfortunately, some IEC/IEEE
-floating-point operations are not defined within ISO/ANSI C. If a machine
-implements such ``non-C'' operations, target-specific subroutines for
-the operations can be supplied to allow TestFloat to test these machine
-features. Typically, such subroutines will need to be written in assembly
-language, although equivalent functions can sometimes be found among the
-system's software libraries.
-
-The following machine functions cannot be tested by TestFloat unless target-
-specific subroutines are supplied for them:
-
- <float>_to_int32 (rounded according to rounding mode)
- <float>_to_int64 (rounded according to rounding mode)
- <float>_round_to_int
- <float>_rem
- <float>_sqrt, except float64_sqrt
- <float>_eq_signaling
- <float>_le_quiet
- <float>_lt_quiet
-
-In addition to these, none of the `floatx80' functions can be tested by
-default if the C `long double' type is something other than extended double
-precision; and likewise, none of the `float128' functions can be tested by
-default if `long double' is not quadruple precision. Since `long double'
-cannot be both extended double precision and quadruple precision at the
-same time, at least one of these types cannot be tested by TestFloat without
-appropriate subroutines being supplied for that type. (On the other hand,
-few systems implement _both_ extended double-precision and quadruple-
-precision floating-point; and unless a system does implement both, it does
-not need both tested.)
-
-Note that the `-list' option to `testfloat' will show the operations
-TestFloat is prepared to test.
-
-TestFloat's `systfloat' module supplies the system version of the functions
-to be tested. The names of the `systfloat' subroutines are the same as the
-function names used as arguments to the `testfloat' command but with `syst_'
-prefixed--thus, for example, `syst_float32_add' and `syst_int32_to_float32'.
-The default `systfloat' module maps these system functions to the standard
-C operations; so `syst_float32_add', for example, is implemented using the
-C `+' operation for the single-precision `float' type. For each system
-function supplied by `systfloat', a corresponding `SYST_<function>'
-preprocessor macro is defined in `systfloat.h' to indicate that the function
-exists to be tested (e.g., `SYST_FLOAT32_ADD'). The `systfloat.h' header
-file also declares function prototypes for the `systfloat' functions.
-
-(The `systfloat.h' file that comes with the TestFloat package declares
-prototypes for all of the possible `systfloat' functions, whether defined in
-`systfloat' or not. There is no penalty for declaring a function prototype
-that is never used.)
-
-A target-specific version of the `systfloat' module can easily be created to
-replace the generic one. This in fact has been done for the example targets
-`386-Win32-gcc' and `SPARC-Solaris-gcc'. For each target, an assembly
-language `systfloat.S' has been created in the target directory along with
-a corresponding `systfloat.h' header file defining the `SYST_<function>'
-macros for the functions implemented. The makefiles of the targets have
-been edited to use these target-specific versions of `systfloat' rather than
-the generic one.
-
-The `systfloat' modules of the example targets have been written entirely
-in assembly language in order to bypass any peculiarities of the C compiler.
-Although this is probably a good idea, it is certainly not required.
-
-
--------------------------------------------------------------------------------
-Steps to Creating the TestFloat Executables
-
-Porting and/or compiling TestFloat involves the following steps:
-
-1. Port SoftFloat and create a SoftFloat binary. (Refer to the
- documentation accompanying SoftFloat.)
-
-2. If one does not already exist, create an appropriate target-specific
- subdirectory under `testfloat' by copying the given `templates'
- directory. The remaining steps occur within the target-specific
- subdirectory.
-
-3. Edit the files `milieu.h' and `Makefile' to reflect the current
- environment.
-
-4. Make `testsoftfloat' by executing `make testsoftfloat' (or `make
- testsoftfloat.exe', or whatever the `testsoftfloat' executable is
- called). Verify that SoftFloat is working correctly by testing it with
- `testsoftfloat'.
-
-If you only wanted `testsoftfloat', you are done. The steps for `testfloat'
-continue:
-
-5. In the target-specific subdirectory, implement the `systmodes' and
- `systflags' modules. (The `syst_float_set_rounding_precision' function
- need not do anything if the system does not support extended double
- precision.)
-
-6. If the target machine supports standard floating-point functions that are
- not accessible within ISO/ANSI C, or if the C compiler cannot be trusted
- to use the machine's floating-point directly, create a target-specific
- `systfloat' module.
-
-7. In the target-specific subdirectory, execute `make'.
-
-
--------------------------------------------------------------------------------
-Improving the Random Number Generator
-
-If you are serious about using TestFloat for testing floating-point, you
-should consider replacing the supplied `random.c' with a better target-
-specific one. The standard C `rand' function is rather poor on some
-systems, and consequently `random.c' has been written to assume very little
-about the quality of `rand'. As a result, the `rand' function is called
-more frequently than it might need to be, shortening the time before
-the random number generator repeats, and possibly wasting time as well.
-If `rand' is better on your system, or if another better random number
-generator is available (such as `rand48' on most Unix systems), TestFloat
-can be improved by overriding the given `random.c' with a target-specific
-one.
-
-
--------------------------------------------------------------------------------
-Contact Information
-
-At the time of this writing, the most up-to-date information about
-TestFloat and the latest release can be found at the Web page `http://
-HTTP.CS.Berkeley.EDU/~jhauser/arithmetic/TestFloat.html'.
-
-