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Go Whole Program LLVM # Go Whole Program LLVM
==================
## Overview
Introduction
------------
This project, gllvm, provides tools for building whole-program (or This project, gllvm, provides tools for building whole-program (or
whole-library) LLVM bitcode files from an unmodified C or C++ whole-library) LLVM bitcode files from an unmodified C or C++
@ -30,11 +30,10 @@ of a build process requires that.
gllvm currently works with clang. gllvm currently works with clang.
Installation ## Installation
------------
Requirements
======= #### Requirements
You need the Go compiler to compile gllvm, and the clang/clang++ executables You need the Go compiler to compile gllvm, and the clang/clang++ executables
to use gllvm. Follow the instructions here to get started: to use gllvm. Follow the instructions here to get started:
@ -46,8 +45,7 @@ by default. It is worth noticing that a standard Go installation will install
the binaries generated for the project under `$GOROOT/bin`. Make sure that you the binaries generated for the project under `$GOROOT/bin`. Make sure that you
added the `$GOROOT/bin` directory to your `$PATH` variable. added the `$GOROOT/bin` directory to your `$PATH` variable.
Build #### Build
=======
First, you must checkout the project under the directory `$GOROOT/src`: First, you must checkout the project under the directory `$GOROOT/src`:
``` ```
@ -60,8 +58,7 @@ To build and install gllvm on your system, type:
make install make install
``` ```
Usage ## Usage
-----
gllvm includes three symlinks to the program's binary: `gclang` and gllvm includes three symlinks to the program's binary: `gclang` and
`gclang++`to compile C and C++, and an auxiliary tool `get-bc` for `gclang++`to compile C and C++, and an auxiliary tool `get-bc` for
@ -91,20 +88,10 @@ Some useful environment variables are listed here:
errors caused by the unexpected production of hidden bitcode files. It is errors caused by the unexpected production of hidden bitcode files. It is
sometimes required when configuring a build. sometimes required when configuring a build.
Preserving bitcode files in a store ## Examples
--------------------------------
Sometimes it can be useful to preserve the bitcode files produced in a ### Building a bitcode module with clang
build, either to prevent deletion or to retrieve them later. If the
environment variable `GLLVM_BC_STORE` is set to the absolute path of
an existing directory, then gllvm will copy the produced bitcode files
into that directory. The name of a copied bitcode file is the hash of the path
to the original bitcode file. For convenience, when using both the manifest
feature of `get-bc` and the store, the manifest will contain both the
original path, and the store path.
Building a bitcode module with clang
------------------------------------
``` ```
tar xf pkg-config-0.26.tar.gz tar xf pkg-config-0.26.tar.gz
@ -121,8 +108,7 @@ get-bc pkg-config
which will produce the bitcode module `pkg-config.bc`. which will produce the bitcode module `pkg-config.bc`.
Building bitcode archive ### Building bitcode archive
------------------------
``` ```
tar -xvf bullet-2.81-rev2613.tgz tar -xvf bullet-2.81-rev2613.tgz
@ -143,8 +129,7 @@ get-bc -b src/LinearMath/libLinearMath.a
produces `src/LinearMath/libLinearMath.a.bc`. produces `src/LinearMath/libLinearMath.a.bc`.
Configuring without building bitcode ### Configuring without building bitcode
------------------------------------
Sometimes it is necessary to disable the production of bitcode. Typically this Sometimes it is necessary to disable the production of bitcode. Typically this
is during configuration, where the production of unexpected files can confuse is during configuration, where the production of unexpected files can confuse
@ -156,8 +141,7 @@ CC=gclang make
``` ```
Building a bitcode archive then extracting the bitcode ### Building a bitcode archive then extracting the bitcode
------------------------------------------------------
``` ```
tar xvfz jansson-2.7.tar.gz tar xvfz jansson-2.7.tar.gz
@ -171,3 +155,42 @@ get-bc libjansson.a
llvm-ar x libjansson.bca llvm-ar x libjansson.bca
ls -la ls -la
``` ```
## Miscellaneous Features
### Preserving bitcode files in a store
Sometimes it can be useful to preserve the bitcode files produced in a
build, either to prevent deletion or to retrieve them later. If the
environment variable `GLLVM_BC_STORE` is set to the absolute path of
an existing directory, then gllvm will copy the produced bitcode files
into that directory. The name of a copied bitcode file is the hash of the path
to the original bitcode file. For convenience, when using both the manifest
feature of `get-bc` and the store, the manifest will contain both the
original path, and the store path.
### Debugging
The GLLVM tools can show various levels of output to aid with debugging.
To show this output set the `GLLVM_OUTPUT_LEVEL` environment
variable to one of the following levels:
* `ERROR`
* `WARNING`
* `INFO`
* `DEBUG`
For example:
```
export GLLVM_OUTPUT_LEVEL=DEBUG
```
Output will be directed to the standard error stream, unless you specify the
path of a logfile via the `GLLVM_OUTPUT_FILE` environment variable.
For example:
```
export GLLVM_OUTPUT_FILE=/tmp/gllvm.log
```