On Fri, 2016-10-28 at 08:31 -0500, Will Schmidt wrote:
> On Fri, 2016-10-28 at 10:38 +0200, Richard Biener wrote:
> > On Thu, Oct 27, 2016 at 5:37 PM, Will Schmidt <will_schm...@vnet.ibm.com>
> > wrote:
> > > Hi,
> > >
> > > Per PR72747, A statement such as "v = vec_splats (1);" correctly
> > > initializes a vector. However, a statement such as "v[1] = v[0] =
> > > vec_splats (1);" initializes both v[1] and v[0] to random garbage.
> > >
> > > It has been determined that this is occurring because we did not emit
> > > the actual initialization statement before our final exit from
> > > gimplify_init_constructor, at which time we lose the expression when we
> > > assign *expr_p to either NULL or object. This problem affected both
> > > constant
> > > and non-constant initializers. Corrected this by moving the logic to
> > > emit the statement up earlier within the if/else logic.
> > >
> > > Bootstrapped and make check ran without regressions on
> > > powerpc64le-unknown-linux-gnu.
> > >
> > > OK for trunk?
> >
> > Ok.
> >
> > RIchard.
>
> Committed revision 241647.
> Thanks.
Oops, forgot to ask. After some burn-in time, is this OK to backport to
the 5 and 6 branches?
The bug was first noticed in GCC 5.
Thanks,
-Will
>
>
> >
> > > Thanks,
> > > -Will
> > >
> > > gcc:
> > > 2016-10-26 Will Schmidt <will_schm...@vnet.ibm.com>
> > >
> > > PR middle-end/72747
> > > * gimplify.c (gimplify_init_constructor): Move emit of constructor
> > > assignment to earlier in the if/else logic.
> > >
> > > testsuite:
> > > 2016-10-26 Will Schmidt <will_schm...@vnet.ibm.com>
> > >
> > > PR middle-end/72747
> > > * c-c++-common/pr72747-1.c: New test.
> > > * c-c++-common/pr72747-2.c: Likewise.
> > >
> > > Index: gcc/gimplify.c
> > > ===================================================================
> > > --- gcc/gimplify.c (revision 241600)
> > > +++ gcc/gimplify.c (working copy)
> > > @@ -4730,24 +4730,23 @@
> > >
> > > if (ret == GS_ERROR)
> > > return GS_ERROR;
> > > - else if (want_value)
> > > + /* If we have gimplified both sides of the initializer but have
> > > + not emitted an assignment, do so now. */
> > > + if (*expr_p)
> > > {
> > > + tree lhs = TREE_OPERAND (*expr_p, 0);
> > > + tree rhs = TREE_OPERAND (*expr_p, 1);
> > > + gassign *init = gimple_build_assign (lhs, rhs);
> > > + gimplify_seq_add_stmt (pre_p, init);
> > > + }
> > > + if (want_value)
> > > + {
> > > *expr_p = object;
> > > return GS_OK;
> > > }
> > > else
> > > {
> > > - /* If we have gimplified both sides of the initializer but have
> > > - not emitted an assignment, do so now. */
> > > - if (*expr_p)
> > > - {
> > > - tree lhs = TREE_OPERAND (*expr_p, 0);
> > > - tree rhs = TREE_OPERAND (*expr_p, 1);
> > > - gassign *init = gimple_build_assign (lhs, rhs);
> > > - gimplify_seq_add_stmt (pre_p, init);
> > > - *expr_p = NULL;
> > > - }
> > > -
> > > + *expr_p = NULL;
> > > return GS_ALL_DONE;
> > > }
> > > }
> > > Index: gcc/testsuite/c-c++-common/pr72747-1.c
> > > ===================================================================
> > > --- gcc/testsuite/c-c++-common/pr72747-1.c (revision 0)
> > > +++ gcc/testsuite/c-c++-common/pr72747-1.c (working copy)
> > > @@ -0,0 +1,16 @@
> > > +/* { dg-do compile } */
> > > +/* { dg-require-effective-target powerpc_altivec_ok } */
> > > +/* { dg-options "-maltivec -fdump-tree-gimple" } */
> > > +
> > > +/* PR 72747: Test that cascaded definition is happening for constant
> > > vectors. */
> > > +
> > > +#include <altivec.h>
> > > +
> > > +int main (int argc, char *argv[])
> > > +{
> > > + __vector int v1,v2;
> > > + v1 = v2 = vec_splats ((int) 42);
> > > + return 0;
> > > +}
> > > +/* { dg-final { scan-tree-dump-times " v2 = { 42, 42, 42, 42 }" 1
> > > "gimple" } } */
> > > +
> > > Index: gcc/testsuite/c-c++-common/pr72747-2.c
> > > ===================================================================
> > > --- gcc/testsuite/c-c++-common/pr72747-2.c (revision 0)
> > > +++ gcc/testsuite/c-c++-common/pr72747-2.c (working copy)
> > > @@ -0,0 +1,18 @@
> > > +/* { dg-do compile } */
> > > +/* { dg-require-effective-target powerpc_altivec_ok } */
> > > +/* { dg-options "-c -maltivec -fdump-tree-gimple" } */
> > > +
> > > +/* PR 72747: test that cascaded definition is happening for non
> > > constants. */
> > > +
> > > +void foo ()
> > > +{
> > > + extern int i;
> > > + __vector int v,w;
> > > + v = w = (vector int) { i };
> > > +}
> > > +
> > > +int main (int argc, char *argv[])
> > > +{
> > > + return 0;
> > > +}
> > > +/* { dg-final { scan-tree-dump-times " w = {i.0_1}" 1 "gimple" } } */
> > >
> > >
> >
>
>
