onews

GCC

This file contains information about GCC releases up to GCC 2.8.1, and
some information about EGCS releases.  For more details of changes in
EGCS releases, and details of changes in GCC 2.95 and more recent
releases, see the release notes on the GCC web site and the file NEWS
which contains the most relevant parts of those release notes in text
form.

Noteworthy changes in GCC for EGCS 1.1.
---------------------------------------

The compiler now implements global common subexpression elimination (gcse) as
well as global constant/copy propagation.  (link to gcse page).

More major improvements have been made to the alias analysis code.  A new
option to allow front-ends to provide alias information to the optimizers
has also been added (-fstrict-aliasing).  -fstrict-aliasing is off by default
now, but will be enabled by default in the future. (link to alias page)

Major changes continue in the exception handling support.  This release
includes some changes to reduce static overhead for exception handling.  It
also includes some major changes to the setjmp/longjmp based EH mechanism to
make it less pessimistic.  And finally, major infrastructure improvements
to the dwarf2 EH mechanism have been made to make our EH support extensible.

We have fixed the infamous security problems with temporary files. 

The "regmove" optimization pass has been nearly completely rewritten.  It now
uses much more information about the target to determine profitability of
transformations.

The compiler now recomputes register usage information immediately before
register allocation.  Previously such information was only not kept up to
date after instruction combination which led to poor register allocation
choices by our priority based register allocator.

The register reloading phase of the compiler has been improved to better
optimize spill code.  This primarily helps targets which generate lots of
spills (like the x86 ports and many register poor embedded ports).

A few changes in the heuristics used by the register allocator and scheduler
have been made which can significantly improve performance for certain
applications.

The compiler's branch shortening algorithms have been significantly improved
to work better on targets which align jump targets.

The compiler now supports the "ADDRESSOF" optimization which can significantly
reduce the overhead for certain inline calls (and inline calls in general).

The compiler now supports a code size optimization switch (-Os).  When enabled
the compiler will prefer optimizations which improve code size over those
which improve code speed.

The compiler has been improved to completely eliminate library calls which
compute constant values.  This is particularly useful on machines which
do not have integer mul/div or floating point support on-chip.

GCC now supports a "--help" option to print detailed help information.

cpplib has been greatly improved.  It is probably useable for some sites now
(major missing feature is trigraphs).

Memory footprint for the compiler has been significantly reduced for certain
pathalogical cases.

Build time improvements for targets which support lots of sched parameters
(alpha and mips primarily).

Compile time for certain programs using large constant initializers has been
improved (affects glibc significantly).

Plus an incredible number of infrastructure changes, warning fixes, bugfixes
and local optimizations.

Various improvements have been made to better support cross compilations.  They
are still not easy, but they are improving.

Target specific NEWS

    Sparc: Now includes V8 plus and V9 support, lots of tuning for Ultrasparcs
           and uses the Haifa scheduler by default.

    Alpha: EV6 tuned, optimized expansion of memcpy/bzero.

    x86: Data in the static store is aligned per Intel recommendations.  Jump
         targets are aligned per Intel recommendations.  Improved epilogue
         sequences for Pentium chips.  Backend improvements which should help
         register allocation on all x86 variants.  Support for PPro conditional
         move instructions has been fixed and enabled.  Random changes
	 throughout the port to make generated code more Pentium friendly.
         Improved support for 64bit integer operations.
         Unixware 7, a System V Release 5 target is now supported.
         SCO OpenServer targets can support GAS.  See gcc/INSTALL for details.

    RS6000/PowerPC: Includes AIX4.3 support as well as PowerPC64 support.  
                    Haifa instruction scheduling is enabled by default now.

    MIPS: Multiply/Multiply-Add support has been largely rewritten to generate
          more efficient code.  Includes mips16 support.

    M68K: Various micro-optimizations and Coldfire fixes.

    M32r: Major improvements to this port.

    Arm: Includes Thumb and super interworking support.

EGCS includes all gcc2 changes up to and including the June 9, 1998 snapshot.


Noteworthy changes in GCC version 2.8.1
---------------------------------------

Numerous bugs have been fixed and some minor performance
improvements (compilation speed) have been made.

Noteworthy changes in GCC version 2.8.0
---------------------------------------

A major change in this release is the addition of a framework for
exception handling, currently used by C++.  Many internal changes and
optimization improvements have been made.  These increase the
maintainability and portability of GCC.  GCC now uses autoconf to
compute many host parameters.

The following lists changes that add new features or targets.

See cp/NEWS for new features of C++ in this release.

New tools and features:

    The Dwarf 2 debugging information format is supported on ELF systems, and
    is the default for -ggdb where available.  It can also be used for C++.
    The Dwarf version 1 debugging format is also permitted for C++, but
    does not work well.

    gcov.c is provided for test coverage analysis and branch profiling
    analysis is also supported; see -fprofile-arcs, -ftest-coverage,
    and -fbranch-probabilities.

    Support for the Checker memory checking tool.

    New switch, -fstack-check, to check for stack overflow on systems that
    don't have such built into their ABI.

    New switches, -Wundef and -Wno-undef to warn if an undefined identifier
    is evaluated in an #if directive.

    Options -Wall and -Wimplicit now cause GCC to warn about implicit int
    in declarations (e.g. `register i;'), since the C Standard committee
    has decided to disallow this in the next revision of the standard;
    -Wimplicit-function-declarations and -Wimplicit-int are subsets of
    this.

    Option -Wsign-compare causes GCC to warn about comparison of signed and
    unsigned values.

    Add -dI option of cccp for cxref.

New features in configuration, installation and specs file handling:

    New option --enable-c-cpplib to configure script.

    You can use --with-cpu on the configure command to specify the default
    CPU that GCC should generate code for.

    The -specs=file switch allows you to override default specs used in
    invoking programs like cc1, as, etc.

    Allow including one specs file from another and renaming a specs
    variable.

    You can now relocate all GCC files with a single environment variable
    or a registry entry under Windows 95 and Windows NT.

Changes in Objective-C:

    The Objective-C Runtime Library has been made thread-safe.

    The Objective-C Runtime Library contains an interface for creating
    mutexes, condition mutexes, and threads; it requires a back-end
    implementation for the specific platform and/or thread package.
    Currently supported are DEC/OSF1, IRIX, Mach, OS/2, POSIX, PCThreads,
    Solaris, and Windows32.  The --enable-threads parameter can be used
    when configuring GCC to enable and select a thread back-end.

    Objective-C is now configured as separate front-end language to GCC,
    making it more convenient to conditionally build it.

    The internal structures of the Objective-C Runtime Library have
    changed sufficiently to warrant a new version number; now version 8.
    Programs compiled with an older version must be recompiled.

    The Objective-C Runtime Library can be built as a DLL on Windows 95
    and Windows NT systems.
    
    The Objective-C Runtime Library implements +load.

The following new targets are supported (see also list under each
individual CPU below):

    Embedded target m32r-elf.
    Embedded Hitachi Super-H using ELF.
    RTEMS real-time system on various CPU targets.
    ARC processor.
    NEC V850 processor.
    Matsushita MN10200 processor.
    Matsushita MN10300 processor.
    Sparc and PowerPC running on VxWorks.
    Support both glibc versions 1 and 2 on Linux-based GNU systems.

New features for DEC Alpha systems:

    Allow detailed specification of IEEE fp support:
      -mieee, -mieee-with-inexact, and -mieee-conformant
      -mfp-trap-mode=xxx, -mfp-round-mode=xxx, -mtrap-precision=xxx
    -mcpu=xxx for CPU selection
    Support scheduling parameters for EV5.
    Add support for BWX, CIX, and MAX instruction set extensions.
    Support Linux-based GNU systems.
    Support VMS.

Additional supported processors and systems for MIPS targets:

    MIPS4 instruction set.
    R4100, R4300 and R5000 processors.
    N32 and N64 ABI.
    IRIX 6.2.
    SNI SINIX.
    
New features for Intel x86 family:

    Add scheduling parameters for Pentium and Pentium Pro.
    Support stabs on Solaris-x86.
    Intel x86 processors running the SCO OpenServer 5 family.
    Intel x86 processors running DG/UX.
    Intel x86 using Cygwin32 or Mingw32 on Windows 95 and Windows NT.

New features for Motorola 68k family:

    Support for 68060 processor.
    More consistent switches to specify processor.
    Motorola 68k family running AUX.
    68040 running pSOS, ELF object files, DBX debugging.
    Coldfire variant of Motorola m68k family.

New features for the HP PA RISC:

    -mspace and -mno-space
    -mlong-load-store and -mno-long-load-store
    -mbig-switch -mno-big-switch

    GCC on the PA requires either gas-2.7 or the HP assembler; for best
    results using GAS is highly recommended.  GAS is required for -g and
    exception handling support.

New features for SPARC-based systems:

    The ultrasparc cpu.
    The sparclet cpu, supporting only a.out file format.
    Sparc running SunOS 4 with the GNU assembler.
    Sparc running the Linux-based GNU system.
    Embedded Sparc processors running the ELF object file format.
    -mcpu=xxx
    -mtune=xxx
    -malign-loops=xxx
    -malign-jumps=xxx
    -malign-functions=xxx
    -mimpure-text and -mno-impure-text

    Options -mno-v8 and -mno-sparclite are no longer supported on SPARC
    targets.  Options -mcypress, -mv8, -msupersparc, -msparclite, -mf930,
    and -mf934 are deprecated and will be deleted in GCC 2.9.  Use
    -mcpu=xxx instead.

New features for rs6000 and PowerPC systems:

    Solaris 2.51 running on PowerPC's.
    The Linux-based GNU system running on PowerPC's.
    -mcpu=604e,602,603e,620,801,823,mpc505,821,860,power2
    -mtune=xxx
    -mrelocatable-lib, -mno-relocatable-lib
    -msim, -mmve, -memb
    -mupdate, -mno-update
    -mfused-madd, -mno-fused-madd

    -mregnames
    -meabi
    -mcall-linux, -mcall-solaris, -mcall-sysv-eabi, -mcall-sysv-noeabi
    -msdata, -msdata=none, -msdata=default, -msdata=sysv, -msdata=eabi
    -memb, -msim, -mmvme
    -myellowknife, -mads
    wchar_t is now of type long as per the ABI, not unsigned short.
    -p/-pg support
    -mcpu=403 now implies -mstrict-align.
    Implement System V profiling.

    Aix 4.1 GCC targets now default to -mcpu=common so that programs
    compiled can be moved between rs6000 and powerpc based systems.  A
    consequence of this is that -static won't work, and that some programs
    may be slightly slower.

    You can select the default value to use for -mcpu=xxx on rs6000 and
    powerpc targets by using the --with-cpu=xxx option when configuring the
    compiler.  In addition, a new options, -mtune=xxx was added that
    selects the machine to schedule for but does not select the
    architecture level.

    Directory names used for storing the multilib libraries on System V
    and embedded PowerPC systems have been shortened to work with commands
    like tar that have fixed limits on pathname size.

New features for the Hitachi H8/300(H):

    -malign-300
    -ms (for the Hitachi H8/S processor)
    -mint32

New features for the ARM:

    -march=xxx, -mtune=xxx, -mcpu=xxx
    Support interworking with Thumb code.
    ARM processor with a.out object format, COFF, or AOF assembler.
    ARM on "semi-hosted" platform.
    ARM running NetBSD.
    ARM running the Linux-based GNU system.

New feature for Solaris systems:

    GCC installation no longer makes a copy of system include files,
    thus insulating GCC better from updates to the operating system.


Noteworthy changes in GCC version 2.7.2
---------------------------------------

A few bugs have been fixed (most notably the generation of an
invalid assembler opcode on some RS/6000 systems).

Noteworthy changes in GCC version 2.7.1
---------------------------------------

This release fixes numerous bugs (mostly minor) in GCC 2.7.0, but
also contains a few new features, mostly related to specific targets.

Major changes have been made in code to support Windows NT.

The following new targets are supported:

	2.9 BSD on PDP-11
	Linux on m68k
	HP/UX version 10 on HP PA RISC (treated like version 9)
	DEC Alpha running Windows NT

When parsing C, GCC now recognizes C++ style `//' comments unless you
specify `-ansi' or `-traditional'.

The PowerPC System V targets (powerpc-*-sysv, powerpc-*-eabi) now use the