llvm dev - Jan 2013 - [LLVMdev] Migrate Project Build system to LLVM BitCode

Hi All,

I am migrating a build system of an existing project from 'Object files'
based executable generation to 'LLVM Bitcode' files based exe generation
and applying OPT pass to LLVM Bitcode. I found out the following 4 step
procedure. Please let me know if this is the right procedure or is there any
other easy way of doing it. I need to modify 'Makefile' accordingly. I
read on some forums about GoldPlugin but I don't know exactly if it would be
useful here:

Original Makefile- Object Files based Build/Link Steps:
clang -g -O2   -o  .libs/mergedexe  file1.o    file2.o   file3.o   -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -ldl -pthread .libs/lib2.so

Proposed Makefile- LLVM Bitcode based Build/Link Steps:

1.       llvm-link -o .libs/mergedbc.bc   file1.bc    file2.bc   file3.bc

2.       opt  -o  optmerged.bc  -load /path/to/Mypass.so  -mypass < 
mergedbc.bc

3.       llc  -o .libs/mergedbc.s    .libs/mergedbc.bc

4.       gcc -g -O2 -o .libs/mergedexe  .libs/mergedbc.s  -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto -ldl -pthread .libs/lib2.so

Thanks.

Ahmad
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Hi Ahmad,

On 17/01/13 14:56, Hassan, Ahmad wrote:
> Hi All,
>
> I am migrating a build system of an existing project from ‘Object files’
based
> executable generation to ‘LLVM Bitcode’ files based exe generation and
applying
> OPT pass to LLVM Bitcode. I found out the following 4 step procedure.
Please let
> me know if this is the right procedure or is there any other easy way of
doing
> it. I need to modify ‘Makefile’ accordingly. I read on some forums about
> GoldPlugin but I don’t know exactly if it would be useful here:
>
> *Original Makefile- Object Files based Build/Link Steps: *
>
> clang -g -O2   –o  .libs/mergedexe  file1.o    file2.o   file3.o   -pthread
> -Wl,--export-dynamic   .libs/lib1.a   -lssl –ldl –pthread .libs/lib2.so
>
> *Proposed Makefile- LLVM Bitcode based Build/Link Steps:*
>
> 1.llvm-link -o .libs/mergedbc.bc   file1.bc    file2.bc   file3.bc
>
> 2.opt  –o  optmerged.bc  -load /path/to/Mypass.so  -mypass < 
mergedbc.bc
>
> 3.llc  -o .libs/mergedbc.s    .libs/mergedbc.bc
>
> 4.gcc -g -O2 -o .libs/mergedexe  .libs/mergedbc.s  -pthread
> -Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto –ldl –pthread
.libs/lib2.so
if you pass -O4 rather than -O2 to clang I think it will in essence do this all
for you already.  It might even do the link time optimization for you at -O2
even, I'm not sure.

Ciao, Duncan.
>
> Thanks.
>
> Ahmad
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>

Hi Duncan,
> 4.gcc -g -O2 -o .libs/mergedexe  .libs/mergedbc.s  -pthread
> -Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto -ldl -pthread
.libs/lib2.so
>if you pass -O4 rather than -O2 to clang I think it will in essence do this
all
>for you already.  It might even do the link time optimization for you at -O2
>even, I'm not sure.
No, if I use clang for producing executable then I get series of error both with
O2 and O4:

error: input can't have .file dwarf directives when -g is used to generate
dwarf debug info for assembly code
        .file   38 "/usr/include/x86_64-linux-gnu/sys/un.h"

If I remove '-g' then I get
/usr/bin/ld: /usr/local/bin/../lib/LLVMgold.so: error loading plugin
/usr/bin/ld: /usr/local/bin/../lib/LLVMgold.so: error in plugin cleanup
(ignored)
clang: error: linker command failed with exit code 1

It works fine if I use 'gcc' in step 4 for produce executable.

Cheers,
Ahmad



Ciao, Duncan.
>
> Thanks.
>
> Ahmad
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
_______________________________________________
LLVM Developers mailing list
LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Ahmad,

   If the Makefile contains only this command, then it is not worth spending
time on GoldPlugin. If you are building a large project, then it will be simpler
to use GoldPlugin.

  The steps you are using seem right. You can possibly combine the last two
steps (3&4) using only 1 clang command.

 clang -g -O2 -o .libs/mergedexe .libs/mergedbc.bc -pthread -Wl,--export-dynamic
.libs/lib1.a   -lssl -lcrypto –ldl –pthread .libs/lib2.so

-Swarup.

________________________________
From: llvmdev-bounces at cs.uiuc.edu [llvmdev-bounces at cs.uiuc.edu] on behalf
of Hassan, Ahmad [ahmad.hassan at sap.com]
Sent: Thursday, January 17, 2013 7:56 AM
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] Migrate Project Build system to LLVM BitCode

Hi All,

I am migrating a build system of an existing project from ‘Object files’ based
executable generation to ‘LLVM Bitcode’ files based exe generation and applying
OPT pass to LLVM Bitcode. I found out the following 4 step procedure. Please let
me know if this is the right procedure or is there any other easy way of doing
it. I need to modify ‘Makefile’ accordingly. I read on some forums about
GoldPlugin but I don’t know exactly if it would be useful here:

Original Makefile- Object Files based Build/Link Steps:
clang -g -O2   –o  .libs/mergedexe  file1.o    file2.o   file3.o   -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl –ldl –pthread .libs/lib2.so

Proposed Makefile- LLVM Bitcode based Build/Link Steps:

1.       llvm-link -o .libs/mergedbc.bc   file1.bc    file2.bc   file3.bc

2.       opt  –o  optmerged.bc  -load /path/to/Mypass.so  -mypass < 
mergedbc.bc

3.       llc  -o .libs/mergedbc.s    .libs/mergedbc.bc

4.       gcc -g -O2 -o .libs/mergedexe  .libs/mergedbc.s  -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto –ldl –pthread .libs/lib2.so

Thanks.

Ahmad
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Hi Swarp,
> clang -g -O2 -o .libs/mergedexe .libs/mergedbc.bc -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto -ldl -pthread .libs/lib2.so
Thanks. This works fine. The project that I am migrating is huge and has various
massive Makefiles. But I am going to try this 3 step approach to apply passes
and compile the code. If that gets too complex then I will move to GoldPlugin.
Thanks.
--Ahmad


-Swarup.
________________________________
From: llvmdev-bounces at cs.uiuc.edu [llvmdev-bounces at cs.uiuc.edu] on behalf
of Hassan, Ahmad [ahmad.hassan at sap.com]
Sent: Thursday, January 17, 2013 7:56 AM
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] Migrate Project Build system to LLVM BitCode
Hi All,

I am migrating a build system of an existing project from 'Object files'
based executable generation to 'LLVM Bitcode' files based exe generation
and applying OPT pass to LLVM Bitcode. I found out the following 4 step
procedure. Please let me know if this is the right procedure or is there any
other easy way of doing it. I need to modify 'Makefile' accordingly. I
read on some forums about GoldPlugin but I don't know exactly if it would be
useful here:

Original Makefile- Object Files based Build/Link Steps:
clang -g -O2   -o  .libs/mergedexe  file1.o    file2.o   file3.o   -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -ldl -pthread .libs/lib2.so

Proposed Makefile- LLVM Bitcode based Build/Link Steps:

1.       llvm-link -o .libs/mergedbc.bc   file1.bc    file2.bc   file3.bc

2.       opt  -o  optmerged.bc  -load /path/to/Mypass.so  -mypass < 
mergedbc.bc

3.       llc  -o .libs/mergedbc.s    .libs/mergedbc.bc

4.       gcc -g -O2 -o .libs/mergedexe  .libs/mergedbc.s  -pthread
-Wl,--export-dynamic   .libs/lib1.a   -lssl -lcrypto -ldl -pthread .libs/lib2.so

Thanks.

Ahmad
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