[llvm-dev] Four bitcode generated with plugin-opt=save-temps

[Muhui Jiang via llvm-dev]

Hi Teresa

Thanks for your very quick and clear explanation. I have one more question.

The emit-llvm option will give you the IR for a single source file when you
compile it with -c. All of those files when combined give the IR in the
preopt.bc temp file.
===========
So if I use "clang -emit-llvm -c" to generate the .ll file. It should be
the same as the one I generated by using "llvm-dis *.preopt.bc -o
*.preopt.ll" to translate the bitcode to IR. Actually, I would like to
obtain the control flow information from the LLVM IR. Will different stages
of the bitcode influence the generated CFG?
Many Thanks

Regards
Muhui

2018-05-15 21:19 GMT+08:00 Teresa Johnson <tejohnson at google.com>:

> These are the bitcode at different stages of the LTO portion of the
> compile. LTO merges the IR for all files being linked and optimizes them as
> a single monolithic module. The preopt.bc is the merged IR just after
> merging and before performing any LTO optimizations. internalize.bc is
> after performing whole program internalization. opt.bc is after the
> optimization pipeline, and .precodegen.bc is immediately before native code
> generation.
>
> The emit-llvm option will give you the IR for a single source file when
> you compile it with -c. All of those files when combined give the IR in the
> preopt.bc temp file.
>
> Hope that helps,
> Teresa
>
> On Tue, May 15, 2018 at 4:43 AM Muhui Jiang via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi
>>
>> I use the LDFLAGS=" -flto -fuse-ld=gold  -Wl,-plugin-opt=save-temps " to
>> generate the makefile and to make the whole program. However,  found four
>> different kinds of bitcode for each target. For example, I am compiling
>> coreutils. For the program "nohup", I can get
>>
>>  nohup.0.0.preopt.bc
>>  nohup.0.2.internalize.bc
>>  nohup.0.4.opt.bc
>>  nohup.0.5.precodegen.bc
>>
>> If I am right, I can also get the bitcode with emit-llvm option in clang.
>> May I know which bc among the above four should be the same as the one I
>> generated with emit-llvm. More information are very thankful.
>>
>> Regards
>> Muhui
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
>  408-460-2413
>
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