From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
gcc-patches List <gcc-patches@gcc.gnu.org>,
"Carlos O'Donell" <carlos@systemhalted.org>
Subject: Re: [PATCH v1] tree-optimization/95821 - Convert strlen + strchr to memchr
Date: Mon, 20 Jun 2022 11:48:24 -0700 [thread overview]
Message-ID: <CAFUsyfLt1h2XxgBOPx1ROodNDeSx_YFTtdvGE=MgdPZDYsiOeQ@mail.gmail.com> (raw)
In-Reply-To: <YrCugNDtftu400fW@tucnak>
On Mon, Jun 20, 2022 at 10:29 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Mon, Jun 20, 2022 at 09:35:36AM -0700, Noah Goldstein via Gcc-patches wrote:
> > This patch allows for strchr(x, c) to the replace with memchr(x, c,
> > strlen(x) + 1) if strlen(x) has already been computed earlier in the
> > tree.
> >
> > Handles PR95821: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95821
> >
> > Since memchr doesn't need to re-find the null terminator it is faster
> > than strchr.
>
> Do you have a GCC Copyright assignment on file, or do you want to submit
> this under DCO ( https://gcc.gnu.org/dco.html )? If the latter, there
> should be a Signed-off-by: line, both in the mail and later commit.
> >
> > bootstrapped and tested on x86_64-linux.
> >
> > gcc/
> >
>
> As it fixes a GCC bugzilla bug, the ChangeLog entry should start with
> PR tree-optimization/95821
> line.
> > * tree-ssa-strlen.cc: Emit memchr instead of strchr if strlen
> > already computed.
>
> All the indented lines in ChangeLog should be indented by tab.
> You are modifying strlen_pass::handle_builtin_strchr function, so after
> tree-ssa-strlen.cc there should be that function name in parens:
> * tree-ssa-strlen.cc (strlen_pass::handle_builtin_strchr): Emit
> memchr ...
>
> >
> > gcc/testsuite/
> >
> > * c-c++-common/pr95821-1.c
> > * c-c++-common/pr95821-2.c
> > * c-c++-common/pr95821-3.c
> > * c-c++-common/pr95821-4.c
> > * c-c++-common/pr95821-5.c
> > * c-c++-common/pr95821-6.c
>
> All the above lines should end with ": New test." after .c
>
> > --- a/gcc/tree-ssa-strlen.cc
> > +++ b/gcc/tree-ssa-strlen.cc
>
> How does the patch relate to the one that H.J. attached in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95821#c4 ?
>
> > @@ -2405,9 +2405,12 @@ strlen_pass::handle_builtin_strlen ()
> > }
> > }
> >
> > -/* Handle a strchr call. If strlen of the first argument is known, replace
> > - the strchr (x, 0) call with the endptr or x + strlen, otherwise remember
> > - that lhs of the call is endptr and strlen of the argument is endptr - x. */
> > +/* Handle a strchr call. If strlen of the first argument is known,
> > + replace the strchr (x, 0) call with the endptr or x + strlen,
> > + otherwise remember that lhs of the call is endptr and strlen of the
> > + argument is endptr - x. If strlen of x is not know but has been
> > + computed earlier in the tree then replace strchr(x, c) to
> > + memchr(x, c, strlen + 1). */
>
> Space before ( even in comments.
>
>
>
> > void
> > strlen_pass::handle_builtin_strchr ()
> > @@ -2418,8 +2421,8 @@ strlen_pass::handle_builtin_strchr ()
> > if (lhs == NULL_TREE)
> > return;
> >
> > - if (!integer_zerop (gimple_call_arg (stmt, 1)))
> > - return;
> > + tree chr = gimple_call_arg (stmt, 1);
> > + bool is_strchr_zerop = integer_zerop (chr);
> >
> > tree src = gimple_call_arg (stmt, 0);
> >
> > @@ -2452,32 +2455,56 @@ strlen_pass::handle_builtin_strchr ()
> > fprintf (dump_file, "Optimizing: ");
> > print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
> > }
> > - if (si != NULL && si->endptr != NULL_TREE)
> > + if (!is_strchr_zerop)
> > {
> > - rhs = unshare_expr (si->endptr);
> > - if (!useless_type_conversion_p (TREE_TYPE (lhs),
> > - TREE_TYPE (rhs)))
> > - rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
> > + /* If its not strchr(s, zerop) then try and convert to
> > + memchr if strlen has already been computed. */
>
> Again, space before (. The second line is weirdly formatted, should
> be indented below If.
>
> > + tree fn = builtin_decl_explicit (BUILT_IN_MEMCHR);
> > + tree one = build_int_cst (TREE_TYPE (rhs), 1);
> > + rhs = fold_build2_loc (loc, PLUS_EXPR, TREE_TYPE (rhs),
> > + unshare_expr (rhs), one);
> > + tree size = make_ssa_name (TREE_TYPE (rhs));
> > + gassign *size_stmt = gimple_build_assign (size, rhs);
> > + gsi_insert_before (&m_gsi, size_stmt, GSI_SAME_STMT);
> > + rhs = size;
> > + if (!update_gimple_call (&m_gsi, fn, 3, src, chr, rhs))
> > + return;
>
> I think we should differentiate more. If integer_nonzerop (chr)
> or perhaps better tree_expr_nonzero_p (chr), then it is better
> to optimize t = strlen (x); ... p = strchr (x, c); to
> t = strlen (x); ... p = memchr (x, c, t);
What do you mean by differentiate more? More comments? Or
seperate the logic more?
> the t + 1 is only needed if c might be zero.
>
> > + /* Don't update strlen of lhs if search-char was non-zero. */
>
> Wasn't known to be zero is the right thing.
>
> Jakub
>
next prev parent reply other threads:[~2022-06-20 18:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-20 16:35 Noah Goldstein
2022-06-20 17:29 ` Jakub Jelinek
2022-06-20 17:54 ` H.J. Lu
2022-06-20 18:48 ` Noah Goldstein [this message]
2022-06-20 19:04 ` Jakub Jelinek
2022-06-20 19:12 ` Noah Goldstein
2022-06-20 19:57 ` Jakub Jelinek
2022-06-20 20:59 ` Noah Goldstein
2022-06-20 21:42 ` [PATCH v2] " Noah Goldstein
2022-06-21 12:01 ` Jakub Jelinek
2022-06-21 18:13 ` Noah Goldstein
2022-07-07 16:26 ` Noah Goldstein
2022-06-21 18:12 ` [PATCH v3] " Noah Goldstein
2022-07-09 15:59 ` Jeff Law
2022-09-21 22:02 ` Noah Goldstein
2022-09-22 12:22 ` Jakub Jelinek
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