llvm dev - Nov 2007 - [LLVMdev] llvm-gcc cannot emit @llvm.pow.* ?

Hi,

Current llvm-gcc cannot emit llvm intrinsic function like llvm.pow.* and
llvm.sin.*
For example:

double foo(double x, double y) {
  return pow(x,y);
}

will compiled into ll:

define double @foo(double %x, double %y) {
   %tmp3 = tail call double @pow( double %x, double %y )
  ret double %tmp3
}

This is not consistent with llvm language reference.
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Hi,
> Current llvm-gcc cannot emit llvm intrinsic function like llvm.pow.* and
> llvm.sin.*
> For example:
> 
> double foo(double x, double y) {
>   return pow(x,y);
> }
> 
> will compiled into ll:
> 
> define double @foo(double %x, double %y) {
>    %tmp3 = tail call double @pow( double %x, double %y )
>   ret double %tmp3
> }
> 
> This is not consistent with llvm language reference.
first of all, this is logically wrong - the language reference
doesn't say anywhere that you *have* to use llvm.pow.* rather than
pow from the C library.  Also, don't forget that the llvm intrinsics
don't set errno, so using them is only valid on systems/for languages
for which errno is ignored.  That said, llvm.pow.* is for raising
to an integer power, and here you raise to a double power.

Ciao,

Duncan.

2007/11/22, Duncan Sands <baldrick at free.fr>:
>
> Hi,
>
> > Current llvm-gcc cannot emit llvm intrinsic function like llvm.pow.*
and
> > llvm.sin.*
> > For example:
> >
> > double foo(double x, double y) {
> >   return pow(x,y);
> > }
> >
> > will compiled into ll:
> >
> > define double @foo(double %x, double %y) {
> >    %tmp3 = tail call double @pow( double %x, double %y )
> >   ret double %tmp3
> > }
> >
> > This is not consistent with llvm language reference.
>
> first of all, this is logically wrong - the language reference
> doesn't say anywhere that you *have* to use llvm.pow.* rather than
> pow from the C library.

Sure. But now the question is the llvm-gcc will not emit llvm.pow.* anytime.

Also, don't forget that the llvm intrinsics
> don't set errno, so using them is only valid on systems/for languages
> for which errno is ignored.  That said, llvm.pow.* is for raising
> to an integer power, and here you raise to a double power.

I don't understand. why we  can't  use llvm.pow.f64 for double power?

Sheng.

Ciao,
>
> Duncan.
>
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