[LLVMdev] Invoking LLVM front-end

[Jeff Kunkel]

I forgot to cc the list

On Mon, Oct 11, 2010 at 6:19 PM, Jeff Kunkel <jdkunk3 at gmail.com> wrote:
> Well this is my 20,000 foot viewpoint of the project you have
> described. Also, I would appreciate if someone more knowledgeable
> revised my statements.
>
> First, I would make a mock machine with large register banks for each
> kind of operation and size combination. The large register bank will
> fool the upper levels because the upper levels only look at register
> pressure and register classes. Since supposedly, you do not want to
> restrict the compiled code into a machine, but instead you wish to
> create the machine.
>
> Second, I would rewrite the whole CodeGen piece of the code because
> SSA form goes into the CodeGen and machine code comes out. Since the
> kind of optimizations the current independent code generator does is
> restricting the SSA form into a certain machine; this does not
> correlate with the goals of your project. While some operations may be
> useful from the codegen like instruction scheduling and instruction
> lowering, you wish to dynamically define which operations to combine
> before lowering. If there are many add followed by a shift, then you
> wish to create the instruction add-shift on the fly. Since, you do not
> know the instructions before hand, you may optimize them accordingly.
>
> From that part onwards, you would have complete control of the code.
>
> As for not being a pass, well yes and no. You can certainly write your
> code as passes into the CodeGen. You may create custom headers with
> your data structures and format your code accordingly, or you may just
> hook into the first and only code gen pass for you mock machine.
>
> My 2 cents,
> Jeff Kunkel
>
>
>
> On Mon, Oct 11, 2010 at 5:42 PM, Taemin Kim <taemin0712 at gmail.com> wrote:
>> Hello LLVMers,
>>
>> I am developing hardware generation tool which converts C/C++ application to
>> hardware which is not a Pass but a separate project. I am going to use LLVM
>> as front-end optimization tool. I am curious how I can invoke the LLVM
>> front-end optimziations and then, get the pointer of LLVM IR data generated
>> by the front-end. I would like to perform some optimziations on the IR. Can
>> anybody please direct me to some example codes or documentation about that?
>>
>> Thank you.
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>>
>