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gfortran.texi: (Current Status): update and rewrite to reflect actual status more accurately.
2006-10-04 Brooks Moses <bmoses@stanford.edu> * gfortran.texi: (Current Status): update and rewrite to reflect actual status more accurately. From-SVN: r117449
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Brooks Moses
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2006-10-04 Brooks Moses <bmoses@stanford.edu>
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* gfortran.texi: (Current Status): update and rewrite to reflect
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actual status more accurately.
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2006-10-04 Brooks Moses <bmoses@stanford.edu>
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* gfortran.texi: Consistently refer to the compiler as "GNU
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@ -374,58 +374,49 @@ the GCC homepage in March 18, 2000
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(even though Andy had already been working on it for a while,
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of course).
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The GNU Fortran compiler is currently reaching the stage where is is able to
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compile real
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world programs. However it is still under development and has many rough
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edges.
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@menu
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* Compiler Status::
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* Library Status::
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* Compiler and Library Status::
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* Proposed Extensions::
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@end menu
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@node Compiler Status
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@section Compiler Status
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@node Compiler and Library Status
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@section Compiler and Library Status
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@table @emph
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@item Front end
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This is the part of the GNU Fortran compiler which parses a source file, verifies that it
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is valid Fortran, performs compile time replacement of constants
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(PARAMETER variables) and reads and generate module files. This is
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almost complete. Every Fortran 95 source should be accepted, and most
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none-Fortran 95 source should be rejected. If you find a source file where
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this is not true, please tell us. You can use the -fsyntax-only switch to
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make @command{gfortran} quit after running the front end, effectively reducing it to
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a syntax checker.
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The GNU Fortran compiler is able to compile nearly all
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standard-compliant Fortran 95, Fortran 90, and Fortran 77 programs,
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including a number of standard and non-standard extensions, and can be
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used on real-world programs. In particular, the supported extensions
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include OpenMP, Cray-style pointers, and several Fortran 2003 features
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such as enumeration, stream I/O, and some of the enhancements to
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allocatable array support from TR 15581. However, it is still under
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development and has a few remaining rough edges.
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@item Middle end interface
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These are the parts of GNU Fortran that take the parse tree generated by the
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front end and translate it to the GENERIC form required by the GCC back
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end. Work is ongoing in these parts of GNU Fortran, but a large part has
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already been completed.
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@end table
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At present, the GNU Fortran compiler passes the
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@uref{http://www.fortran-2000.com/ArnaudRecipes/fcvs21_f95.html,
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NIST Fortran 77 Test Suite}, and produces acceptable results on the
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@uref{http://www.netlib.org/lapack/faq.html#1.21, LAPACK Test Suite}.
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It also provides respectable performance on
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the @uref{http://www.polyhedron.com/pb05.html, Polyhedron Fortran
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compiler benchmarks} and the
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@uref{http://www.llnl.gov/asci_benchmarks/asci/limited/lfk/README.html,
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Livermore Fortran Kernels test}. It has been used to compile a number of
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large real-world programs, including
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@uref{http://mysite.verizon.net/serveall/moene.pdf, the HIRLAM
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weather-forecasting code} and
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@uref{http://www.theochem.uwa.edu.au/tonto/, the Tonto quantum
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chemistry package}.
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@node Library Status
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@section Library Status
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Among other things, the GNU Fortran compiler is intended as a replacement
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for G77. At this point, nearly all programs that could be compiled with
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G77 can be compiled with GNU Fortran, although there are a few minor known
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regressions.
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Some intrinsic functions map directly to library functions, and in most
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cases the name of the library function used depends on the type of the
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arguments. For some intrinsics we generate inline code, and for others,
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such as sin, cos and sqrt, we rely on the backend to use special
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instructions in the floating point unit of the CPU if available, or to
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fall back to a call to libm if these are not available.
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The primary work remaining to be done on GNU Fortran falls into three
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categories: bug fixing (primarily regarding the treatment of invalid code
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and providing useful error messages), improving the compiler optimizations
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and the performance of compiled code, and extending the compiler to support
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future standards -- in particular, Fortran 2003.
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Implementation of some non-elemental intrinsic functions (eg. DOT_PRODUCT,
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AVERAGE) is not yet optimal. This is hard because we have to make decisions
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whether to use inline code (good for small arrays as no function call
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overhead occurs) or generate function calls (good for large arrays as it
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allows use of hand-optimized assembly routines, SIMD instructions, etc.)
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The IO library is in a mostly usable state. Unformatted I/O for
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@code{REAL(KIND=10)} variables is currently not recommended.
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Array intrinsics mostly work.
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@node Proposed Extensions
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@section Proposed Extensions
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@ -437,11 +428,9 @@ J3 Fortran 95 standard.
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@subsection Compiler extensions:
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@itemize @bullet
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@item
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Flag for defining the kind number for default logicals.
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@item
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User-specified alignment rules for structures.
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@item
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Flag to generate @code{Makefile} info.
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@ -452,10 +441,6 @@ Automatically extend single precision constants to double.
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Compile code that conserves memory by dynamically allocating common and
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module storage either on stack or heap.
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@item
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Flag to cause the compiler to distinguish between upper and lower case
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names. The Fortran 95 standard does not distinguish them.
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@item
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Compile flag to generate code for array conformance checking (suggest -CC).
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@ -472,31 +457,12 @@ Flag to force local variables into static space.
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@item
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Flag to force local variables onto stack.
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@item
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Flag to compile lines beginning with ``D''.
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@item
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Flag to ignore lines beginning with ``D''.
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@item
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Flag for maximum errors before ending compile.
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@item
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Generate code to check for null pointer dereferences -- prints locus of
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dereference instead of segfaulting. There was some discussion about this
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option in the g95 development mailing list.
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@item
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Allow setting the default unit number.
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@item
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Option to initialize otherwise uninitialized integer and floating
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point variables.
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@item
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Support for Fortran 200x. This includes several new features including
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floating point exceptions, extended use of allocatable arrays, C
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interoperability, Parameterizer data types and function pointers.
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@end itemize
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@ -545,6 +511,11 @@ Environment variable forcing standard output to be line buffered (unix).
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@end itemize
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@c ---------------------------------------------------------------------
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@c Runtime
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@c ---------------------------------------------------------------------
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@node Runtime
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@chapter Runtime: Influencing runtime behavior with environment variables
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@cindex Runtime
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