[LLVMdev] promotion of return value.

[Rafael Espindola]

2009/3/12  <Alireza.Moshtaghi at microchip.com>:
> What I was planning to do is to provide a default behavior that is
> consistent with what currently llvm does (promote to 32 bit)
> And then there will be control in clang for targets to do things
> differently.
> But I also understand you concern about gcc frontend; because the same
> thing has to also take place there....
> We had long discussions about this last year, and this is what has been
> decided. Maybe Chris is in a better position to decide what to do.

Can you take a look at my last post on the bug and see if that could work
for all the cases you have? Since llvm-gcc and clang are the ones doing
the lowering, i think it would. Consider the code

----------------------
short x;
void g(int);
short h(void);
short f(void) {
  g(h());
  return x;
}
--------------------

For X86, I think llvm IL for f can be
------------------------------------------
define i16 @f() nounwind {
entry:
       %0 = tail call i16 @h() nounwind
       %1 = sext i16 %0 to i32
       tail call void @g(i32 %1) nounwind
       %2 = load i16* @x, align 2
       ret i16 %2
}
--------------------------------------

and for arm it can be

----------------------------------------
define i32 @f() nounwind {
entry:
       %0 = tail call i32 @h() nounwind
       tail call void @g(i32 %0) nounwind
       %2 = load i16* @x, align 2
       %3 = sext i16 %2 to i32
       ret i32 %3
}
--------------------------------------

Note that for X86 only the caller does extension. For ARM only the
callee does it.

> A.

Cheers,
-- 
Rafael Avila de Espindola

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