This directory contains the sources of GHDL, the VHDL simulator.

GHDL fully supports IEEE 1076-1987, IEEE 1076-1993, IEE 1076-2002 and
partially the 1076-2008 version of VHDL.

GHDL is free software.  See the file COPYING for copying permission.
The manuals, and some of the runtime libraries, are under different
terms; see the individual source files for details.

Building GHDL (Short instructions)
**********************************

If you aren't on linux, see below for full instructions.

You need GNAT GPL 2014 (or later) for x86 (32 bits).  GNAT is the GNU Ada
compiler and GNAT GPL is very easy to install (just untar and run the
doinstall script).

In the GHDL source directory, configure and build:
$ ./configure
$ make

At that place, you can already use the 'ghdl_mcode' built in the directory.
You can also install GHDL (the executable is installed as 'ghdl'):
$ make install

That's all!

Build GHDL (Long instructions)
******************************

GHDL supports many backend (code generator), so you first must choose
the backend you want to use.  There are currently 3 supported backends:

* gcc
* mcode (this is an internal code generator for i386)
* llvm (experimental)

Here is a short comparaison:

* gcc:
+ generated code is faster (particularly with -O or -O2)
+ generated code can be debugger (with -g)
+ the output is an executable
+ ported to many platforms (x86, x86_64, powerpc, sparc)
- analyze can takes time (particularly for big units)
- build is more complex

* mcode
+ easy to build
- but i386 only
+ very quick analysis time
+ can analyze very big designs
- simulation is slower
- no executable created

* llvm
- still experimental
+ same advantages of gcc (good generated code, debuggable)
+ easier to build than gcc

As GCC is written in Ada, you need to use the GNU Ada compiler (GNAT).
I recommend to use GNAT GPL from http://libre.adacore.com (free).
GHDL was tested with GNAT GPL 2014.  Any later version should work.
If you build with the mcode backend, you need an i386 version of GNAT.

Building with mcode backend
***************************

This is as simple as:
$ ./configure --prefix=PREFIX
  where PREFIX is the directory for installation
$ make
  This builds the ghdl_mcode executable, which can be used as is.
$ make install
  To install within PREFIX

Building with the gcc backend
*****************************

You need to download and untar the sources of
gcc version 4.9 [do not modify this line as this is read by scripts].

First configure ghdl and specify gcc source dir:
$ ./configure --with-gcc=/path/to/gcc/source/dir

Then invoke make to copy ghdl sources in the source dir:
$ make copy-sources

Finally configure gcc following the gcc instructions and don't forget to
enable the vhdl language (you can use --enable-languages=c,vhdl
--disable-bootstrap)

Building with the llvm backend
******************************

You need to build and install
llvm version 3.5 [do not modify this line as this is read by scripts].

First configure ghdl and specify where llvm is installed
$ ./configure --with-llvm=PREFIX
  where PREFIX/bin/llvm-config is present

Notes for developpers
*********************

Developping with the gcc backend:
Once gcc (with ghdl) has been built once, it is possible to work on ghdl
sources tree without copying them in gcc tree. Commands are:
$ make ghdl1-gcc     	     # To build the compiler
$ make ghdl_gcc		     # To build the driver
$ make libs.vhdl.gcc	     # To compile the vhdl libraries
$ make grt-all		     # To build the ghdl runtime
$ make grt.links	     # To locally install the ghdl runtime
TODO: gcc object dir