Hi Andrew,
> -----Original Message-----
> From: Andrew Pinski [mailto:pins...@gmail.com]
> Sent: Friday, October 30, 2015 3:38 PM
> To: Kumar, Venkataramanan
> Cc: Richard Beiner (richard.guent...@gmail.com); gcc-patches@gcc.gnu.org
> Subject: Re: [RFC] [Patch] Relax tree-if-conv.c trap assumptions.
>
> On Fri, Oct 30, 2015 at 6:06 PM, Kumar, Venkataramanan
> <venkataramanan.ku...@amd.com> wrote:
> > Hi Richard,
> >
> > I am trying to "if covert the store" in the below test case and later
> > help it to get vectorized under -Ofast -ftree-loop-if-convert-stores
> > -fno-common
> >
> > #define LEN 4096
> > __attribute__((aligned(32))) float array[LEN]; void test() { for (int i =
> > 0; i <
> LEN; i++) {
> > if (array[i] > (float)0.)
> > array[i] =3 ;
> >
> > }
> > }
> >
> > Currently in GCC 5.2 does not vectorize it.
> > https://goo.gl/9nS6Pd
> >
> > However ICC seems to vectorize it
> > https://goo.gl/y1yGHx
> >
> > As discussed with you earlier, to allow "if convert store" I am checking
> > the
> following:
> >
> > (1) We already read the reference "array[i]" unconditionally once .
> > (2) I am now checking if we are conditionally writing to memory which is
> defined as read and write and is bound to the definition we are seeing.
>
>
> I don't think this is thread safe ....
>
I thought under -ftree-loop-if-convert-stores it is ok to do this
transformation.
Regards,
Venkat.
> Thanks,
> Andrew
>
> >
> > With this change, I get able to if convert and the vectorize the case also.
> >
> > /build/gcc/xgcc -B ./build/gcc/ ifconv.c -Ofast -fopt-info-vec -S
> > -ftree-loop-if-convert-stores -fno-common
> > ifconv.c:2:63: note: loop vectorized
> >
> > Patch
> > ------
> > diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c index
> > f201ab5..6475cc0 100644
> > --- a/gcc/tree-if-conv.c
> > +++ b/gcc/tree-if-conv.c
> > @@ -727,6 +727,34 @@ write_memrefs_written_at_least_once (gimple
> *stmt,
> > return true;
> > }
> >
> > +static bool
> > +write_memrefs_safe_to_access_unconditionally (gimple *stmt,
> > +
> > +vec<data_reference_p> drs) {
> > + int i;
> > + data_reference_p a;
> > + bool found = false;
> > +
> > + for (i = 0; drs.iterate (i, &a); i++)
> > + {
> > + if (DR_STMT (a) == stmt
> > + && DR_IS_WRITE (a)
> > + && (DR_WRITTEN_AT_LEAST_ONCE (a) == 0)
> > + && (DR_RW_UNCONDITIONALLY (a) == 1))
> > + {
> > + tree base = get_base_address (DR_REF (a));
> > + found = false;
> > + if (DECL_P (base)
> > + && decl_binds_to_current_def_p (base)
> > + && !TREE_READONLY (base))
> > + {
> > + found = true;
> > + }
> > + }
> > + }
> > + return found;
> > +}
> > +
> > /* Return true when the memory references of STMT won't trap in the
> > if-converted code. There are two things that we have to check for:
> >
> > @@ -748,8 +776,20 @@ write_memrefs_written_at_least_once (gimple
> > *stmt, static bool ifcvt_memrefs_wont_trap (gimple *stmt,
> > vec<data_reference_p> refs) {
> > - return write_memrefs_written_at_least_once (stmt, refs)
> > - && memrefs_read_or_written_unconditionally (stmt, refs);
> > + bool memrefs_written_once, memrefs_read_written_unconditionally;
> > + bool memrefs_safe_to_access;
> > +
> > + memrefs_written_once
> > + = write_memrefs_written_at_least_once (stmt, refs);
> > +
> > + memrefs_read_written_unconditionally
> > + = memrefs_read_or_written_unconditionally (stmt, refs);
> > +
> > + memrefs_safe_to_access
> > + = write_memrefs_safe_to_access_unconditionally (stmt,
> > + refs);
> > +
> > + return ((memrefs_written_once || memrefs_safe_to_access)
> > + && memrefs_read_written_unconditionally);
> > }
> >
> > /* Wrapper around gimple_could_trap_p refined for the needs of the
> >
> >
> > do I need this function write_memrefs_written_at_least_once anymore?
> > Please suggest if there a better way to do this.
> >
> > Bootstrapped and regression tested on x86_64.
> > I am not adding change log and comments now, as I wanted to check
> approach first.
> >
> > Regards,
> > Venkat.
> >
> >
