On Mon, Jun 20, 2022 at 10:29 AM Jakub Jelinek <ja...@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 ...
Fixed in v2. > > > > > 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 Fixed in V2. > > > --- 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. Fixed in V2. > > > > > 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. Fixed in V2. > > > + 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); > the t + 1 is only needed if c might be zero. Done in V2. Also added the optimizations if chr has zero-char bits. Right now: t=strlen (s); strchr (s, 0) -> t; strchr (s, 256) -> t; strchr (s, 1234) -> memchr (s, 1234, t); strchr (s, non_zero) -> memchr (s, non_zero, t); strchr (s, unknown) -> memchr (s, unknown, t + 1); > > > + /* Don't update strlen of lhs if search-char was non-zero. */ > > Wasn't known to be zero is the right thing. Fixed in V2. > > Jakub >
