This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [patch i386]: Expand sibling-tail-calls via accumulator register

----- Original Message -----
> On Wed, May 28, 2014 at 03:54:58PM -0600, Jeff Law wrote:
> > >Why not get rid of all the above 4 lines and just keep:
> > >
> > >>   return CONSTANT_P (op);
> > >
> > >?  CONST matches CONSTANT_P, and what is inside of CONST should be
> > >fine, and (plus (symbol_ref) (const_int)) not surrounded by CONST
> > >ir invalid.
> > Haven't we recently had problems with being overly accepting of
> > stuff inside CONST when using the CONST for address expressions.
> > ISTM we should only accept what the processor supports here.
> The only recent problem I remember was that we forgot to put CONST
> around (plus (symbol_ref) (const_int)), but I see no problem not
> accepting such invalid RTL.
> The processor shouldn't care, for the instructions a CONST is just
> any kind of immediate, what exactly it is matters solely to the
> assembler/linker and dynamic linker
> (if there are relocations for it, if the expression can be expressed in
> the assembly, etc.).  But that is common to all CONST operands, there is
> nothing special particularly about sibcalls.
> 	Jakub

Well, actually we want to prevent to accept anything plus/mult within memory-addresses, which hasn't a symbol-ref, or a constant-value as arguments.  Is it for sure that there are within a CONST-rtx no registers?  If so, we could check intitally for CONSTANT_P.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]