Porting Clang to a new architecture

Ariel Arelovich via cfe-commits cfe-commits at lists.llvm.org
Mon Oct 26 08:58:46 PDT 2015


So this is what I wanted to know. I think understand what you are saying.
You are saying that most of the work that I would need to do from the AST
(I'm assuming that this stands from Abstract Syntax Tree) is allready being
done by LLVM and I should look to modify for a my new arquitecture. Right?

If I take the AST and process it myself to generate the opcodes, I'm
essentially writing LLVM just less efficient (no optimizations) and
specific for the new architecure, right?

On Mon, Oct 26, 2015 at 12:32 PM, Saleem Abdulrasool <compnerd at compnerd.org>

> On Monday, October 26, 2015, Ariel Arelovich via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>> Hi:
>> Where I'm working I've been asked to look into developing a C (by this I
>> mean C89 C standard) compiler a new processor architecture being created
>> inhouse.
>> On looking at the options and brushing up on compiler theory, I came up
>> with Flex/Bison, Writing the compiler from scratch or use Clang. I liked
>> this option better because parsing and and analyzing c code to genereate
>> somthing intermediate, and do this from scratch, seemed like reinventing
>> the wheel (an incredibly complex wheel, at that).
>> I've figured that if Clang, works with the standard compiler flow (that
>> I've seen everywhere), it takes a C program and transforms it until it gets
>> a intermediate language (which is machine independant). The Dragon Book,
>> even calls this the output of the compiler Front End. From what I've read
>> from the documentation This is what Clang is: a compiler front end. LLVM
>> does optimization and translation to opcodes of known architectures. Is
>> this correct? Or am I getting this wrong?
> Correct.  clang is just the front end for C-like languages.  It will parse
> and analyze the code (generating the AST).  The IR it generates is the LLVM
> IR.
> So, my question is: Would it be possible to use Clang in such a way that
>> it takes a C program and generates an intermediate language so that I can
>> work directly on that language to generate opcodes based on the
>> architecture that we are currently developing?
> Yes.  This is how clang already works.  It sounds like you should be
> looking at LLVM, not clang since you are trying to support a new
> architecture, not a language feature.
>> Thank you, for any answers.
>> PD: I know my question might be very hard to answer as it is not very
>> specific. All I'm asking for, here, is a simple: "It could be done, start
>> reading about this and that" or "It will be next to impossible, just try
>> something else" (with a little explanation as to why, if that were
>> possible, please).
> --
> Saleem Abdulrasool
> compnerd (at) compnerd (dot) org
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