[LLVMdev] another problem with function arguments aligment

[Chris Lattner]

On Tue, 27 Feb 2007, Lauro Ramos Venancio wrote:
> I think, we must move function arguments lowering from frontend to
> LLVM core. This lowering is generating machine dependent bytecode. See
> http://llvm.org/bugs/show_bug.cgi?id=1230

I agree.  There are two pieces to this as I see it:

1. Make calling conventions easier to nail down.  I just completed as
    series of changes that allows basic calling conventions to be described
    in the .td file for targets.  I've converted the X86/X86-64 backends
    over so far, I'll do PPC and others will do darwin/ARM in time.  Here
    is the X86 calling conv description:
http://llvm.org/cvsweb/cvsweb.cgi/llvm/lib/Target/X86/X86CallingConv.td?rev=HEAD&content-type=text/x-cvsweb-markup

    I will document this when I have time.

2. We need to stop llvm-gcc from lowering aggregates to scalar values in
    the front-end.  To do this, we need some thoughtful extensions to LLVM.
    This is nontrivial, but important.  I don't have immediate plans to do
    this, but it's on my mid-range-term todo list.  Switching targets over
    to use #1 is a prerequisite.

-Chris

> 2007/2/26, Chris Lattner <sabre at nondot.org>:
>> On Mon, 26 Feb 2007, Lauro Ramos Venancio wrote:
>>> The problem is: llvm-gcc generates the same bytecode for both functions:
>>>
>>> declare void @f(i32, i64)
>>> declare void @g(i32, i64)
>>>
>>> I can't differ an i64 argument from a struct argument.
>>
>> Oops.  You can fix this by changing llvm-gcc: gcc/llvm-abi.h
>>
>> Grep for instances of Int64Ty there.  I can help answer any q's you might
>> have.
>>
>> -Chris
>>
>> --
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-Chris

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