I'm cross-posting this from the cfe-dev list [I know nothing about this, just that the questions seem to be the same]
Date: Thu, 29 Nov 2018 09:48:58 +0100
From: Alex Denisov via cfe-dev <
cfe-dev@lists.llvm.org>
To: David Greene <
dag@cray.com>
Cc: "
cfe-dev@lists.llvm.org" <
cfe-dev@lists.llvm.org>
Subject: Re: [cfe-dev] Getting LLVM IR from clang
Message-ID: <
268D2CEC-AFC2-4F32-94FE-E445E882A00D@gmail.com>
Content-Type: text/plain; charset=us-ascii
Hi David,
There are at least two robust ways to get the Bitcode/IR:
1. LTO. You can enable link-time optimization by adding -flto compiler
flags, in the end all object files (*.o) will in fact be bitcode files.
I.e.:
> file gmock.dir/gmock-gtest-all.cc.o
gmock.dir/gmock-gtest-all.cc.o: LLVM bitcode, wrapper x86_6
2. Embedded bitcode. Clang 3.9 and higher has an option -fembed-bitcode.
When enabled, the resulting executable will contain additional section
containing bitcode.
You can use this great tool[1] to extract the bitcode from an executable.
Both approaches produce bitcode (binary format), if you need IR
(human-readable format), then you can post-process the bitcode by
running llvm-dis against each bitcode file.
I hope it helps.
[1]
https://github.com/JDevlieghere/LibEBC
> On 28. Nov 2018, at 23:22, David Greene via cfe-dev <
cfe-dev@lists.llvm.org> wrote:
>
> How do I get the LLVM IR produced by clang? I know that -emit-llvm
> produces IR but it seems to be after processing by LLVM (things are
> optimized out, for example). Is there an "official" way to get the IR
> coming right out of clang's codegen? I can do a hack with -mllvm
> -print-before-all but that's icky.
>
> Thanks!
>
> -David
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