llvm dev - Apr 2009 - [LLVMdev] Calling Conventions, function prologs and epilogs.

How/where are function prologs and epilogs generated, is it bespoke C++ code or
TableGen generated ?

If someone could point me in the right direction please.

Many thanks in advance,

Aaron
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Aaron Gray wrote:
> How/where are function prologs and epilogs generated, is it bespoke C++ 
> code or TableGen generated ?
Each target seems to define a RegisterInfo::emitPrologue and 
RegisterInfo::emitEpilog function that is called by the 
lib/CodeGen/PrologueEpilogueInserter.cpp transformation.

Hope this helps,
Luke
>  
> If someone could point me in the right direction please.
>  
> Many thanks in advance,
>  
> Aaron
>  
> 
> 
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Hello, Aaron
> How/where are function prologs and epilogs generated, is it bespoke C++
code
> or TableGen generated ?
>
> If someone could point me in the right direction please.
Calling convention is really-really far from prologue/epilogue emission :) So:

1. Calling conventions
Partly tablegen / partly C++ code. Look for
CodeGen/SelectionDAG/CallingConvLower.cpp,
Target/X86/X86CallingConv.td and around. Usually this code is run
during different phases of sdag lowering.

2. Prologue / epilogue.
Pure C++ code. Look into CodeGen/PrologEpilogInserter.cpp (quite
obviously, right?) with bunch of target-specialized hooks, for
example, ones located in Target/X86/X86RegisterInfo.cpp. Information
about this is needed on different stages, some - even before regalloc,
some - in the late end of the codegen.

Hope this will help.

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

On Thu, Apr 9, 2009 at 4:34 PM, Anton Korobeynikov
<anton at korobeynikov.info>wrote:
> Hello, Aaron
>
> > How/where are function prologs and epilogs generated, is it bespoke
C++
> code
> > or TableGen generated ?
> >
> > If someone could point me in the right direction please.
> Calling convention is really-really far from prologue/epilogue emission :)
> So:
>
> 1. Calling conventions
> Partly tablegen / partly C++ code. Look for
> CodeGen/SelectionDAG/CallingConvLower.cpp,
> Target/X86/X86CallingConv.td and around. Usually this code is run
> during different phases of sdag lowering.
>
> 2. Prologue / epilogue.
> Pure C++ code. Look into CodeGen/PrologEpilogInserter.cpp (quite
> obviously, right?) with bunch of target-specialized hooks, for
> example, ones located in Target/X86/X86RegisterInfo.cpp. Information
> about this is needed on different stages, some - even before regalloc,
> some - in the late end of the codegen.
>
> Hope this will help.
>
Yes, great. One other question. AFAICS this does not allow specialization
say for a new Windows platform (Not MinGW or Cygwin) /Target to produce
different code from X86 Linux.

Thanks,

Aaron
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