[LLVMdev] running a module pass via opt on multiple bitcode files

[John Criswell]

On 9/22/11 4:04 PM, Jinwook Shin wrote:
> Thanks John. I appreciate your help.

De nada.

>
> I have taken the libLTO approach and it worked like a charm :) For 
> those who wanted to achieve the same thing, below are the steps I've 
> taken.
>
> John --  a small question: I thought I wouldn't need to touch 
> Makefiles at all, but that wasn't the case. Could you take a look at 
> Step 4) and tell me what you think? Thanks!

A properly written project will allow the person compiling the software 
to easily change the compiler and the compiler/linker flags used.

For example, autoconf-based configure scripts usually use the following 
environment variables:

CC - C compiler
CXX - C++ compiler
CFLAGS - compiler flags
LDFLAGS - linker flags

So, you would do the following in sh/ksh syntax:

CC=llvm-gcc
CXX=llvm-g++
CFLAGS="-emit-llvm"
export CC
export CXX
export CFLAGS
./configure


>
> 1) Create your own libLTO and add your pass to it. Do a code diff 
> between /safecode/tools/LTO/LTOCodeGenerator.cpp 
> and /llvm/tools/lto/LTOCodeGenerator.cpp to figure out what changes 
> are needed to do this.
> 2) Make a backup copy of the original linker  /usr/lib/libLTO.dylib.
> 3) Copy your libLTO.dylib to /usr/lib.
> 4) Open Makefiles in your target project and change CC and CFLAGS as 
> follows:
> CC=llvm-gcc
> CFLAGS=-emit-llvm …
> 5) Build the project with LLVM.

-- John T.

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