[tree-ssa] RFC: Never gimplify ASM_EXPRs

[Andrew Haley]

Paul Koning writes:
 > >>>>> "Andrew" == Andrew Haley <aph@redhat.com> writes:
 > 
 >  Andrew> Richard Henderson writes:
 >  >> On Thu, Jun 05, 2003 at 04:35:56PM +0100, Andrew Haley wrote: >
 >  >> Diego Novillo writes: > > Is this an invalid use of __asm__ then?
 >  >> 
 >  >> I don't think so.
 >  >> 
 >  >> > I think so.  The asm is asking for a mem operand for something
 >  >> that it > never intends actually to access.
 >  >> 
 >  >> It DID access it.  With a prefetch instruction.
 > 
 >  Andrew> Not really; a prefetch instruction is more of a suggestion
 >  Andrew> than an access, is it not?
 > 
 > NO!  A prefetch instruction, in those architectures where it is
 > implemented, is NOT a suggestion, it's an order to do real work.

I think we both understand what prefetch does.  The crucial difference
here is that the RHS must *not* be fully evaluated -- if the operand
specifies an invalid memory address, no exception occurs, and the
instruction has no effect.

Andrew.