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: [PING][PATCH] LRA: check_rtl modifies RTL instruction stream

On Wed, Nov 20, 2013 at 11:18:49AM -0700, Jeff Law wrote:
> >2013-11-13  Robert Suchanek  <>
> >
> >     	* lra.c (lra): Set lra_in_progress before check_rtl call.
> >     	* recog.c (insn_invalid_p): Add !lra_in_progress to prevent
> >     	adding clobber regs when LRA is running

Trying to run the testsuite with -mlra and the default -mcmodel=medium
on powerpc64 now results in enormous numbers of failures like the

/home/alanm/src/gcc-virgin/libatomic/testsuite/libatomic.c/atomic-exchange-1.c:67:1: error: insn does not satisfy its constraints:
(insn 5 2 6 2 (set (reg/f:DI 212)
        (mem/u/c:DI (unspec:DI [
                    (symbol_ref/u:DI ("*.LC0") [flags 0x2])
                    (reg:DI 2 2)
                ] UNSPEC_TOCREL) [0 S8 A8])) /home/alanm/src/gcc-virgin/libatomic/testsuite/libatomic.c/atomic-exchange-1.c:14 505 {*movdi_internal64}
     (expr_list:REG_EQUAL (symbol_ref:DI ("v") <var_decl 0x3fff9bd00850 v>)

This is due to that innocuous seeming change of setting
lra_in_progress before calling check_rtl(), in combination with
previous changes Vlad made to the rs6000 backend here:
In particular the "Call legitimate_constant_pool_address_p in strict
mode for LRA" change, that sets "strict" when lra_in_progress.

I'm not at all familiar with lra so why Vlad made those changes to
rs6000.c is totally opaque to me.  If this were a reload problem I
could dive in and fix it, but not lra, sorry..

What I can say is that the rtl shown above is a toc reference of the
form that is valid for -mcmodel=small both before and after reload,
and generates "ld offset(r2)" machine instructions.  The form is valid
for -mcmodel=medium/large only before reload.  After reload it is
supposed to be split into high/lo_sum variants that generate
"addis rtmp,offset@ha(r2); ld offset@l(rtmp)".

Alan Modra
Australia Development Lab, IBM

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