RE: [Patch] Add MIPS flag to avoid use of ldc1/sdc1/ldxc1/sdxc1

["Moore, Catherine" <Catherine_Moore at mentor dot com>]

> -----Original Message-----
> From: Andrew Pinski [mailto:pinskia@gmail.com]
> Sent: Monday, October 27, 2014 6:32 PM
> To: Steve Ellcey
> Cc: Moore, Catherine; Matthew Fortune; GCC Patches
> Subject: Re: [Patch] Add MIPS flag to avoid use of ldc1/sdc1/ldxc1/sdxc1
> 
> On Mon, Oct 27, 2014 at 3:23 PM, Steve Ellcey <sellcey@imgtec.com> wrote:
> >
> > There are some MIPS patches that have been applied to the Google
> > Android GCC tree but not been submitted to FSF GCC.  I would like to get
> those patches
> > checked in if possible.   The first one is to add a new MIPS flag to turn
> > off the use of ldc1/sdc1/ldxc1/sdxc1.  Google Earth has a custom
> > allocator that does not guarantee 8 byte alignment of the allocated
> > memory, therefore using these instructions (that require 8 byte
> > alignment) could cause runtime failures.  By default, these
> > instructions will continue to be used, the flag is there to allow their use to
> be turned off if desired.
> 
> That sounds like a bug in google earth's allocator if we follow either C or C++
> standards when it comes to malloc/operator new.
> Both have to be align enough for the type which is at least that size that is
> being allocated.  So it needs to be 8byte aligned if allocating a 8 byte object.
> 

  Andrew,

  Do you have an objection to allowing an option to disable these instructions (despite the reason for wanting to do so)?

  Thanks,
  Catherine
  
> 
> >
> > Tested on mips-mti-linux-gnu.
> >
> > OK to checkin?
> >
> > Steve Ellcey
> > sellcey@imgtec.com
> >
> >
> >
> > 2014-10-27  Steve Ellcey  <sellcey@imgtec.com>
> >
> >         * config/mips/mips.h (ISA_HAS_LDC1_SDC1): Check
> TARGET_LDC1_SDC1.
> >         * config/mips/mips.md (*<ANYF:loadx>_<P:mode): Ditto.
> >         * config/mips/mips.md (*<ANYF:storex>_<P:mode): Ditto.
> >         * config/mips/mips.opt (mldc1-sdc1): New.
> >
> >
> > diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h index
> > c7b998b..b9caff7 100644
> > --- a/gcc/config/mips/mips.h
> > +++ b/gcc/config/mips/mips.h
> > @@ -892,7 +892,8 @@ struct mips_cpu_info {
> >  /* ISA has LDC1 and SDC1.  */
> >  #define ISA_HAS_LDC1_SDC1      (!ISA_MIPS1                             \
> >                                  && !TARGET_MIPS5900                    \
> > -                                && !TARGET_MIPS16)
> > +                                && !TARGET_MIPS16                      \
> > +                                && TARGET_LDC1_SDC1)
> >
> >  /* ISA has the mips4 FP condition code instructions: FP-compare to CC,
> >     branch on CC, and move (both FP and non-FP) on CC.  */ diff --git
> > a/gcc/config/mips/mips.md b/gcc/config/mips/mips.md index
> > d47bb78..77f3356 100644
> > --- a/gcc/config/mips/mips.md
> > +++ b/gcc/config/mips/mips.md
> > @@ -4573,7 +4573,7 @@
> >    [(set (match_operand:ANYF 0 "register_operand" "=f")
> >         (mem:ANYF (plus:P (match_operand:P 1 "register_operand" "d")
> >                           (match_operand:P 2 "register_operand"
> > "d"))))]
> > -  "ISA_HAS_LXC1_SXC1"
> > +  "ISA_HAS_LXC1_SXC1 && (<MODE>mode == SFmode ||
> TARGET_LDC1_SDC1)"
> >    "<ANYF:loadx>\t%0,%1(%2)"
> >    [(set_attr "type" "fpidxload")
> >     (set_attr "mode" "<ANYF:UNITMODE>")]) @@ -4582,7 +4582,7 @@
> >    [(set (mem:ANYF (plus:P (match_operand:P 1 "register_operand" "d")
> >                           (match_operand:P 2 "register_operand" "d")))
> >         (match_operand:ANYF 0 "register_operand" "f"))]
> > -  "ISA_HAS_LXC1_SXC1"
> > +  "ISA_HAS_LXC1_SXC1 && (<MODE>mode == SFmode ||
> TARGET_LDC1_SDC1)"
> >    "<ANYF:storex>\t%0,%1(%2)"
> >    [(set_attr "type" "fpidxstore")
> >     (set_attr "mode" "<ANYF:UNITMODE>")]) diff --git
> > a/gcc/config/mips/mips.opt b/gcc/config/mips/mips.opt index
> > dca4f80..7b75fc9 100644
> > --- a/gcc/config/mips/mips.opt
> > +++ b/gcc/config/mips/mips.opt
> > @@ -267,6 +267,10 @@ mips3d
> >  Target Report RejectNegative Var(TARGET_MIPS3D)  Use MIPS-3D
> > instructions
> >
> > +mldc1-sdc1
> > +Target Report Var(TARGET_LDC1_SDC1) Init(1) Use ldc1/ldxc1 and
> > +sdc1/sdxc1 instruction
> > +
> >  mllsc
> >  Target Report Mask(LLSC)
> >  Use ll, sc and sync instructions