llvm dev - Feb 2013 - [LLVMdev] c-like language implementation using llvm

Hi,

I have a project where I am creating a language which is very similar to C, but
has some extensions. Among the most important are:
1) A new 1-bit data-type
2) Some gates: NOT, AND, etc.. that act on arrays of this 1-bit type. (Think
like a hardware description language.) These are like external function calls,
which don't have an implementation for now.

I don't have a particular target, and would like to translate to the LLVM IR
format for now. I want to leverage the power of LLVM SSA
transformation/optimization framework. I would like to know your opinion about
my approach:

1) I have already added a new type to clang's lexer/parser for my high-level
language. Do I need to add a new type to LLVM IR as well? I read some warnings
about this being difficult to implement. As far as I understand, there is
structural typing in LLVM. Can I just utilize the i1 type? Is the i1 type
already used for something, and thus might create a conflict?

2) Can I use LLVM's intrinsic functions for my gates, something like
@llvm.NOT(i1 %val)? Would the fact that the implementation of these external
functions is not defined, create a problem in translation down to IR? I have
used Clang's "built-ins" in the front-end and that seems to do the
job at the parser level.


Thanks,
Ali

PS. Just to clarify again, this is not intended as an addition to LLVM's
codebase. It's solely for my own purpose.
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20130203/34a6a917/attachment.html>

> Can I just utilize the i1 type? Is the
> i1 type already used for something, and thus might create a conflict?
I think you are very confused. LLVM's types are meant to be used to
represent *your* program :) They can't be "already used".
> 2) Can I use LLVM's intrinsic functions for my gates, something like
> @llvm.NOT(i1 %val)? Would the fact that the implementation of these
external
> functions is not defined, create a problem in translation down to IR? I
have
> used Clang's "built-ins" in the front-end and that seems to
do the job at
> the parser level.
Again, I think you are confused. Just use the operations that are
built into LLVM, such as
<http://llvm.org/docs/LangRef.html#bitwise-binary-operations>. One
slight point of confusion is that LLVM tries to be minimal so there is
no NOT instruction; `NOT X` is represented as `XOR X, -1`. You
probably won't need to add an intrinsic unless you are doing something
_very_ exotic.

-- Sean Silva

Hi Sean,
>> Can I just utilize the i1 type? Is the
>> i1 type already used for something, and thus might create a conflict?
> 
> I think you are very confused. LLVM's types are meant to be used to
> represent *your* program :) They can't be "already used".
I am keeping all the types of C, and adding my new types. I thought that, for
example, I can't map my new type to i32 because that's used for C
integers. That's what I meant by already used. Am I missing something?
> 
>> 2) Can I use LLVM's intrinsic functions for my gates, something
like
>> @llvm.NOT(i1 %val)? Would the fact that the implementation of these
external
>> functions is not defined, create a problem in translation down to IR? I
have
>> used Clang's "built-ins" in the front-end and that seems
to do the job at
>> the parser level.
> 
> Again, I think you are confused. Just use the operations that are
> built into LLVM, such as
> <http://llvm.org/docs/LangRef.html#bitwise-binary-operations>. One
> slight point of confusion is that LLVM tries to be minimal so there is
> no NOT instruction; `NOT X` is represented as `XOR X, -1`. You
> probably won't need to add an intrinsic unless you are doing something
> _very_ exotic.
> 
That's a good point. However simple binary operations such as XOR are not
the only ones I'll be using. I have the Toffoli Gate for example which takes
in 3 operands:
http://en.wikipedia.org/wiki/Toffoli_gate
I guess I can use intrinsics for these things? If I do, can I leave its behavior
undefined? I would like it to appear just with the name toffoli in the IR.

Thanks,
Ali
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20130203/e7691633/attachment.html>