llvm dev - Sep 2015 - Introspecting the calling convention and triple

Hi

assume, that you know the calling convention of a function and the 
target-triple of the destination. You also know the types of the parameters.

How would you go about finding out, which machine register or stack 
offset/size will be used for those parameters, if they will be zero 
extended or not ?

Ciao
    Nat!

P.S. Apologies, for this being something somewhat of a cross-post, a bit 
reworded from an unanswered mail in cfe-dev :)

Hi,

The triple doesn't really tell you much about the desired target but I
won't go into that here. There's an explanation at
http://lists.llvm.org/pipermail/llvm-dev/2015-July/087700.html.

I'm not sure how you'd extract the information you want from this but I
can point you at the right code. At the clang level, you can find some of this
using *ABIInfo::classifyReturnType() and *ABIInfo::classifyArgumentType(). These
functions tell clang how to lower to LLVM-IR and specifies whether the
return/argument is passed indirectly or not, sign/zero/not extended, etc. The
code responsible for assigning registers, stack slots, etc. in the backend is in
*TargetLowering::LowerCall(), *TargetLowering::LowerFormalArguments(), and
*TargetLowering::LowerReturn().

Hope that helps
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
Nat!
> via llvm-dev
> Sent: 17 September 2015 21:55
> To: llvm-dev
> Subject: [llvm-dev] Introspecting the calling convention and triple
> 
> Hi
> 
> assume, that you know the calling convention of a function and the
> target-triple of the destination. You also know the types of the
parameters.
> 
> How would you go about finding out, which machine register or stack
> offset/size will be used for those parameters, if they will be zero
> extended or not ?
> 
> Ciao
>     Nat!
> 
> P.S. Apologies, for this being something somewhat of a cross-post, a bit
> reworded from an unanswered mail in cfe-dev :)
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