GHDL

free and open-source analyzer, compiler, simulator and (experimental) synthesizer for VHDL

[2025-06-17] 5.1

• Improve release management

• Add llvm-jit build

[2025-03-01] 5.0

• Fix some crashes on errors on Windows x64 with mcode backend

• Multiple minor fixes and improvements

[2024-04-14] 4.1

• The mcode backend is now fully supported on Windows x64

• Coverage output has been improved for being supported by vunit.

[2024-03-06] 4.0

• For the mcode backend, elaboration of the designs is now performed before code generation. This allows some optimizations and the support of external names.

• There is a new signal dumper (using FST format) for the mcode backend.

• The GCC backend will be deprecated and the LLVM backend will be used like the mcode backend (code generation in memory). As a consequence, no backend will generate object files anymore.

[2023-03-08] 3.0

• Handle IEEE operators for static expressions.

• Improved support of VHDL 2008 (still!).

• Start support of VHDL 2019 (--std=19).

• pyGHDL:

  • Experimental support to preserve VHDL code comments for documentation extraction.

  • Experimental packaging with a platform-specific shared library for standalone installation using PIP.

  • DOM: dependency graphs, instantiation graphs (design hierarchy), file dependencies (compile order).

• Pre-releases are published to GitHub Releases and assets are uploaded to pre-releases and releases.

[2023-03-06] 3.0.0-rc.4

See 3.0.

[2022-02-28] 2.0

• Improvements to VHDL 2008 supports and synthesis.

[2021-02-02] 1.0

• Python bindings overhauled and renamed to pyGHDL. Three modules are included: libghdl, lsp and dom.

• Utility scripts in the codebase moved into subdir scripts: CI, binding generation, vendors, etc.

• Repository ghdl/ghdl-cosim created. It contains documentation and code examples related to VHPIDIRECT, VPI and SystemC.

• GitHub Action ghdl/setup-ghdl-ci created, to allow easy installation of nightly GHDL assets in GitHub Actions workflows.

• Main documentation site(s) moved to ghdl.github.io/ghdl and ghdl.github.io/ghdl-cosim.

• Repository ghdl/extended-tests created for testing vendors build scripts.

• Logo updated (org, ghdl/ghdl, ghdl/docker and ghdl/ghdl-cosim).

• Assets not added to releases or pre-releases anymore. Users should use package managers or nightly assets (updated after each successful CI run of branch master): nightly.

[2021-01-31] 1.0.0rc1

See 1.0.

[2020-05-21] Nightly build assets

• After each successful CI run of branch master, packages are published as assets of pre-release nightly.

• GitHub Action ghdl/setup-ghdl-ci was created, to allow easy installation of nightly GHDL assets in GitHub Actions workflows.

[2020-05-09] New repositories and a wiki

• The plugin for Yosys was moved from tgingold/ghdlsynth-beta to ghdl/ghdl-yosys-plugin.

• Repository ghdl/ghdl-cosim was created. It contains documentation and code examples related to VHPIDIRECT, VPI and SystemC. See Co-simulation with GHDL and Previous work and future ideas.

• A Wiki was created. The roadmap and ideas for documentation and internship programs were moved there. If you want to contribute anyhow, have a look!

[2020-02-28] 0.37

• Python binding added

• Experimental support of synthesis (either with –synth or with the Yosys plugin)

• Fixes and improved support of VHDL 2008

  • PSL keywords are directly handled in VHDL 2008

• Add support for assume.

• Last version that supports the Mentor variation of std_logic_arith. The Synopsys one is still available.

[2019-03-03] 0.36

• More support of unbounded arrays and records.

• Support of UVVM and VUnit.

[2019-02-23] 0.36-rc1

See 0.36.

[2018-11-29] 20181129

[2017-12-20] GitHub organization

A new GitHub organization is created and the main repo is moved from github.com/tgingold/ghdl to github.com/ghdl/ghdl. Old refs will continue working, because permanent redirects are set up. However, we suggest every contributor to update the remote URLs in their local clones.

[2017-12-14] 0.35

• Assert and report messages are sent to stdout (#394)

• Improve support for unbounded records

• Bugs fixed

[2017-08-15] 0.34

• Display stack backtraces on errors or assert failures

• Compile scripts for vendor libraries (Xilinx, Altera, osvvm, vunit)

• Use SSE2 for mcode backend

• mcode backend ported to x86_64

• Support cocotb potentialventures/cocotb

• Main repository is now on github: github.com/tgingold/ghdl

• Docs available on rtd: ghdl.readthedocks.org

• Speed improved.

• New option --psl-report, to report status of PSL assert and cover.

• VHDL2008: support nested package

[2015-10-23] 0.33

• Improve support of VHDL2008

• Support OSVVM 2015

• Support VUnit: LarsAsplund/vunit

• Many bugs fixed

[2014-11-XX] 0.32

• Updated to build with gcc-4.9.2.

• support:

  • partial of VHDL2008 (available with --std=08):

  • new std.env package.

  • added features in std.textio package

  • all standard IEEE packages.

  • new operations (relation operators, maximum and minimum, unary reduction operators)

  • boolean_vector, integer_vector, real_vector.

  • process(all).

  • generic packages and interface package declarations.

  • block comments (aka delimited comments)

  • implicitly defined to_string functions.

  • OSVVM 2014_01

• Bugs fixed

[2014-01-XX] 0.31

• Updated to build with gcc-4.8.2.

• Supports OSVVM (Open-Source VHDL Verification Methodology) (see osvvm.org) in its VHDL-2002 form.

• Adds 'image and 'value attributes for all required datatypes

• Many bugs and support issues fixed.

• New home on https://sourceforge.net/projects/ghdl-updates/

0.30

Never released, switch to Dunoon Edition.

[2010-01-09] 0.29

• Initial implementation of embedded PSL assertions.

• Improve:

  • speed of non-sensitized processes.

  • speed of string case statement (dichotomy instead of linear search).

• bug fix:

  • and improvements in SDF annotator.

  • when the bound of a string literal type is not locally static.

  • gcov crash

[2009-09-17] 0.28

• Add --std=08 to enable VHDL2008 features.

• Support all-sensitized processes from VHDL2008.

• Documentation typos (thanks to Peter Huewe).

• bug fix:

  • handle 'pos/'leftof/'rightof/'succ/'pred in concurrent statements.

  • overloaded resolution functions.

  • direct drivers elaboration for unconstrained array signals.

  • many minor bugs.

[2008-07-01] 0.27

• Improve SDF annotation (handles much more annotations)

• Add --ieee-asserts= option to control assert messages from ieee packages.

• bug fix:

  • aliases in port map

  • crash during elaboration for top entities with ports/generic

  • crash when string literal in aggregate.

  • concatenation with an array subtype element.

  • non-static subtype used by type conversions in associations.

  • clear timeout in wait for.

  • minor bugs.

[2007-04-08] 0.26

• GHDL_PREFIX environment variable overrides default installation prefix.

• simulation speed improved with ‘direct drivers’.

• windows version:

  • exceptions are caught

  • use executable path instead of registry for prefix

• bug fix:

  • individual association by expression (was not working)

  • individual association of string

  • within windows code generator

  • [windows] large local variables crashed

  • crash when overloaded aggregate target.

  • forbid individual association with open

  • crash when bad array prefix

  • correctly extract sensitivity of record aggregate

[2006-08-11] 0.25

• VPI functions to schedules values.

• math_real now works under windows.

• documentation updated for windows.

• filename/line number displayed for range error during signal update.

• bug fix:

  • ieee math libraries available when --ieee=synopsys.

  • 'image in package bodies.

  • scan of fp literals.

  • interface identifier is checked for conformance rules.

  • avoid a crash in case of error in configuration specification.

  • non-static choice in unidim case are now correctly checked.

  • do not crash in case of bad use of incomplete type.

  • 'range are not expressions.

  • handle file declaration in concurrent procedure calls.

  • correctly handle static 'image attribute.

  • handle in-conversion for signal associated with an expression.

  • emit an error when a function tries to exit without a return.

[2006-06-25] 0.24

• Handle enums with more than 256 elements.

• Relax expr static rules in 93c to analyze Xilinx core lib from 8.1

• man page, ghdl.1, added.

• windows installer improved

• bug fix:

  • correctly handle empty file name.

  • correctly handle unused subprograms of protected types.

  • avoid a crash if unused library are used.

  • avoid crashes during error reports.

  • add a missing case array conversion.

  • build on x86_64.

  • code generated for conversion after mod/rem (windows version).

  • -fexplicit crashed with std.standard functions.

  • handle recursion of pure/wait checks.

  • correctly handle error cases of user attributes

  • time and character read procedure of std.textio.

  • initialize by value parameters (instead of copy-in).

[2006-05-16] 0.23

• bug fix:

  • handle implicit conversion in resolution functions.

  • missing implicit conversion added.

  • avoid a crash in error.

[2006-03-28] 0.22

• direntry added in ghdl.texi

• updated:

  • Documentation (explain bug in Xilinx unisim library).

  • to gcc 4.1

  • math_real

• bug fix:

  • avoid crash if type conversion is indexed/sliced

  • do not allow anymore uncomplete individual association

  • missing check on array association

  • check bounds for val attribute on enumerated type

  • array inequality of locally static expressions evaluated

  • configuration issue

  • --warn-no-vital-generic is now working

[2005-12-18] 0.21

• local optimizations (loops, indexed name).

• simulation speed improved by 20% due to processes mngt optimizations.

• stack-switching code ported to x86_64 (amd64/em64t).

• stack-switching code ported to ia64.

• --syn-binding option extended (see documentation).

• bug fix:

  • line number for some bound violation messages.

  • improved message error for deferred constants.

  • file parameter for functions.

  • universal real divided by integer handled in locally static expr.

  • std_ulogic types and arrays are known by VPI.

  • missing space added in VCDs for integers.

  • CR+LF is also end of line for std.textio.readline.

  • avoid a crash if parse error on choice.

  • handle 'image in nested subprograms.

  • handle 'image for floating point types.

  • do not use varargs C calls.

  • handle missing EOL for readline.

  • for x86_64

0.20 [2005-10-15]

• stack memory usage improved for shortcut operations.

• gtkwave now displays nice waves for bit and std_ulogic signals.

• time unit is displayed in assert/report message.

• -fexplicit option added.

• integers are now written in VCD files.

• hash table added for design_units (speed optimization).

• range checks slightly optimized.

• --vcdz run time option added.

• improved error message for invalid expressions.

• grt now compiles with GNAT-GPL-2005 (use a GNAT bug work-around).

• bug fix:

  • handle more types for --dump-rti and --wave.

  • 'last_event and 'last_active (bad value returned when no previous event or activity).

  • 'image attribute for physical types (was bad unit).

  • 'image attribute for locally static integers.

  • for reading .ghw files.

  • in --xref.

[2005-08-17] 0.19

• ADAFLAGS has been replaced by GHDL_ADAFLAGS to ease compilation.

• ieee.math_real and ieee.math_complex added (only partially, based on a draft).

• current time is printed with assert/report messages.

• stack switch assembly code ported to powerpc-linux.

• documentation on how to use grt from Ada added.

• allow indexes of indexed names to be non-static in case statements (93c only) (this is not standard, but I can’t see why it should be required).

• unbound ports of entities are now reported with --warn-binding.

• some error or warning messages improved.

• --wave option added to dump waveforms (using ghw file format).

• bug fix:

  • internal error (missing close_temp for implicit read)

  • --xref-html: avoid to reanalyze unit.

  • handle implicit conversion for 'image.

  • aggregate assigned to an aggregate: avoid crash.

  • array attributes on unconstrained array: avoid crash.

  • 'last_event returns time'high if no event.

  • 'last_event on array (uninitialized variable).

  • allow calling rising_edge with a port of mode buffer.

  • allow aliases of unconstrained arrays.

  • bound error on aggregate with an unused other association.

  • catch indexed/sliced component (was crashing).

  • catch index/slice of a type conversion (was crashing).

  • handle bad component specification in conf (was crashing).

  • missing ports in component (was crashing).

  • component configurations were dicarded by bug in some cases.

  • no more unused warnings for subprograms in architectures (they may be used in configuration).

  • allow conversion in component configuration.

  • conversion in associations with not statically defined array signals.

[2005-03-12] 0.18

• Keep last line number to speed-up line number look-up (improvement).

• --warn-default-binding added, --warn-binding rewritten.

• 'value implemented for integer numbers.

• bug fix:

  • in textio.read for time.

  • file_close does not crash if file was already closed.

  • spurious unused warnings for protected types.

  • allow subtype names in slice during sensitivity extraction.

  • correctly set the default value of collapsed ports.

  • handling of stack2 (aka large concatenation bug).

[2005-02-26] 0.17

• command --elab-run added.

• Code generation for aggregate improved.

• Library name of option --work= is checked.

• --no-run option added to prevent simulation (may be used to disp tree only).

• disp signal name in error when multiple sources drive an unresolved signal.

• -m/--gen-makefile now handle several libraries.

• dependencies are not stored anymore in libraries (shorter/faster).

• mentor version of ieee library is now provided.

• handling of universal types is more consistent with LRM (almost corner cases).

• iterator and indexes whose bounds were universal expressions are now of type integer or erroneous, according to the weird LRM rules.

• handle selected name as entity name in architecture/configuration.

• bug fix:

  • port map with expression (corner case ?).

  • forbid empty extended identifiers.

  • enumeration literal xrefs.

  • non-object name in sensitivity list crashed.

  • correctly handle alias of signals in processes.

[2005-01-02] 0.16

• std.textio: readline has no limits on line length.

• command -r (run) added.

• bug fix:

  • better handling of errors in type conversion.

  • few uninitialized variables in ghdl itself caught.

  • parse error: begin in aggregates.

  • bad unused subprogram warnings.

[2004-10-13] 0.15

• library file format modified to handle relative pathes.

• install fixed to use relative pathes.

• internal change: ortho API modified (constant are not anymore expressions).

[2004-08-29] 0.14

• pretty printing in HTML command, --pp-html, added.

• xref generation in HTML command, --xref-html, added.

• syntax checking command, -s, added.

• Code generation in whole command, -c files -e unit, added.

• warns for unused subprograms.

• bug box added to help bug reports.

• -s (syntax check) command added.

• Missing grt subprogram to close non-text file added.

• maximum line length of std.textio.readline extended to 512 characters.

• std.textio.readline assert error on truncated lines.

• Handle P32 and P64 in --trace-signals

• sequentials statements are not canonicalized (should be faster).

• DESTDIR added in Makefile to ease packaging.

• for -m command, re-parse modified files of the work library.

• Many checks added on interfaces.

• Many checks added on associations, better handling of conversions.

• Checks for unassociated entity ports at elaboration.

• bug fix:

  • resolution function can be an expanded name.

  • missing type check in a corner case.

  • emit an error when EOF is reached while a text file is read.

  • std.textio.read for negative number.

  • std.textio.read [integer]: correctly handle end of line.

  • parameters of protected type: handled and checked.

  • gen_tree.c modified to work with sparc.

[2004-06-26] 0.13

• support of 64bits integers and 32bits time (not yet user available)

• handle 'high and 'low attributes on non-locally static types and subtypes.

• Many warning switches added (to control output of warnings).

• --gen-makefile mode added to ghdl (to generate a Makefile)

• alias identifier restrictions of vhdl-02 implemented.

• declarative region for architecture from vhdl-02 implemented.

• buffer port association rules of vhdl-02 implemented.

• method operator restrictions of vhdl-02 implemented.

• 'driving and 'driving_value implemented.

• run-time bound check error message now contains file name and line number.

• strings are not stored anymore with the identifiers.

• parser does not back-track anymore.

• bug fix:

  • name clash in generated .s files (arch and port/generic names).

  • implicit conversion of signal parameters.

  • handle locally static type conversion of arrays.

  • stabilize during elaboration of an unconstrained signal.

  • revert previous vhdl87 conf spec bug fix, according to INT-1991 issue 27.

  • multiple visibility of declarations (eg: direct and alias).

  • names attribute of non-object aliases.

[2004-05-30] 0.12

• simulation speed improved (2 fold) due to reduced activity optimization.

• type conversion handled in associations

• make mode of ghdl improved.

• bug fix:

  • attribute specification

  • allow discrete type marks in choices

  • handling of generate statement for VCD

  • allow dereference in variable associations

  • allow function conversion in block port map

  • vhdl87: apply configuration specification inside generate stmts.

  • catch non-passive concurrent procedure calls in entity.

  • association of an unconstrained port with an expression.

  • declaring an uncons. array subtype of an uncons. array subtype.

[2004-04-24] 0.11.1

• bug fix:

  • corner case of signal not updated

  • handle 'stable, 'quiet with a parameter > 0

  • typos (missing + ) in sparc.S

[2004-04-17] 0.11

• signal collapsing improved.

• simulation kernel speed improved (maybe 5x faster).

• --lines mode of ghdldrv added.

• boolean signals are now dumped in vcd files.

• bug fix:

  • in code generation for an aggregate.

  • run-time check of ascending order of projected transactions.

  • empty sequence of stmts in case alternatives (unidim array).

  • evaluation of locally static ‘range attribute.

  • implicit conversion in formal function convertor.

  • return type is a type mark.

[2004-02-28] 0.10

• architecture with many instances can be compiled with less memory.

• --stats option added to the simulator, to evaluate performance.

• signals are now collapsed between instances, if possible.

• simulation is about 3x faster.

• sparc port available (source only).

• more checks added for attribute specification.

• chop command added (split files by design unit).

• bug fix:

  • absolute source files.

  • empty sequence of statements in case alternatives.

[2004-02-01] 0.9

• VITAL level 0 restrictions checks added.

• VITAL 2000 packages provided.

• run-time information (such as signal names) rewritten.

• SDF support added (partial and experimental).

• bug fix:

  • allow elaboration even if no package body if the package is present in a file but not used by the hierarchy.

  • delay_length range is pre-elaborated (was not in v93).

  • crashed when a design unit is not found at elaboration.

  • allow association of 'stable, 'quiet… with signal interfaces.

  • concurrent procedure call creates a non-sensitized process.

  • effective value of non-scalar resolved signal might not be set.

[2003-11-05] 0.8

• protected types (from 1076a/1076-2000) implemented.

• file declarations are finalized in subprograms.

• an exit call-back has been added in the run-time library.

• internal modifications (nodes are stored in a table).

• name of generated executable can be set with -o option.

• IVI (ivi.sourceforge.org) support through a few VPI subprograms.

• pure and wait checks added.

• out ports are correctly dumped in VCD files.

• bug fix:

  • signal declaration not allowed in processes.

  • several bugs fixed.

[2003-08-02] 0.7

• layout of internal nodes improved.

• incremental binding (vhdl93).

• association of in port with expressions (vhdl93).

• --disp-time option added.

• make mode (ghdl -m) rewritten.

• 'simple_name, 'path_name and 'instance_name added (vhdl93).

• bug fix:

  • instantiation added in hierarchy.

  • individual association of subelements by expression.

  • --stop-delta option is working.

  • correctly handle operators names at function call.

  • several small bugs fixed.

[2003-06-09] 0.6

• internal modifications (single linked list used instead of arrays).

• Mentor version of std_logic_arith is provided.

• postponed handled (vhdl 93).

• declarations allowed in a generate statement (vhdl 93).

• non object aliases handled (vhdl93).

• signatures handled (vhdl93).

• bug fix:

  • xnor on bit and boolean is working.

  • selected_name list in use clauses.

  • many other small bug fixes.

[2003-05-10] 0.5

• foreign attribute handled. You can now call subprograms defined in a foreign language (such as C or Ada).

• ghdl entry point added: you can start the VHDL simulation from your own program.

• bug fix:

  • triple use.

  • incomplete types

[2003-04-07] 0.4.1

• bug fix: in the vcd output.

[2003-04-02] 0.4

• libgrt does not depend on GNAT library anymore. Installation requirements are reduced.

• 'delayed attribute implemented.

• 'transaction attribute implemented.

• unaffected (from vhdl-93) implemented.

• ghdl action --disp-standard prints the std.standard package.

• exponentiation operator, **, implemented for all integer and floating point types.

• many other small bug fixes.

• bug fix: subprogram interfaces are now elaborated.