On Tue, Aug 13, 2019 at 10:18 AM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> Thanks for doing this.
>
> Matthew Beliveau <mbeli...@redhat.com> writes:
> > diff --git gcc/tree-ssa-dse.c gcc/tree-ssa-dse.c
> > index 5b7c4fc6d1a..dcaeb8edbfe 100644
> > --- gcc/tree-ssa-dse.c
> > +++ gcc/tree-ssa-dse.c
> > @@ -628,11 +628,8 @@ dse_optimize_redundant_stores (gimple *stmt)
> > tree fndecl;
> > if ((is_gimple_assign (use_stmt)
> > && gimple_vdef (use_stmt)
> > - && ((gimple_assign_rhs_code (use_stmt) == CONSTRUCTOR
> > - && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (use_stmt)) == 0
> > - && !gimple_clobber_p (stmt))
> > - || (gimple_assign_rhs_code (use_stmt) == INTEGER_CST
> > - && integer_zerop (gimple_assign_rhs1 (use_stmt)))))
> > + && initializer_zerop (gimple_op (use_stmt, 1), NULL)
> > + && !gimple_clobber_p (stmt))
> > || (gimple_call_builtin_p (use_stmt, BUILT_IN_NORMAL)
> > && (fndecl = gimple_call_fndecl (use_stmt)) != NULL
> > && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET
> > @@ -1027,15 +1024,13 @@ dse_dom_walker::dse_optimize_stmt
> > (gimple_stmt_iterator *gsi)
> > {
> > bool by_clobber_p = false;
> >
> > - /* First see if this store is a CONSTRUCTOR and if there
> > - are subsequent CONSTRUCTOR stores which are totally
> > - subsumed by this statement. If so remove the subsequent
> > - CONSTRUCTOR store.
> > + /* Check if this store initalizes zero, or some aggregate of zeros,
> > + and check if there are subsequent stores which are subsumed by this
> > + statement. If so, remove the subsequent store.
> >
> > This will tend to make fewer calls into memset with longer
> > arguments. */
> > - if (gimple_assign_rhs_code (stmt) == CONSTRUCTOR
> > - && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (stmt)) == 0
> > + if (initializer_zerop (gimple_op (stmt, 1), NULL)
> > && !gimple_clobber_p (stmt))
> > dse_optimize_redundant_stores (stmt);
> >
>
> In addition to Jeff's comment, the original choice of gimple_assign_rhs1
> is the preferred way to write this (applies to both hunks).
And the !gimple_clobber_p test is now redundant.
> Richard
