On Tue, Apr 19, 2016 at 6:32 PM, Wilco Dijkstra <wilco.dijks...@arm.com> wrote:
> Richard Biener wrote:
>>
>> This folding should be added to gimple-fold.c:gimple_fold_builtin instead,
>> the builtins.c foldings are purerly for folding to constants nowadays.
>
> So is this better? It's a lot more verbose for something so simple...
> Unfortunately match.pd doesn't support this kind of thing either.
Better - comments below. Jakub objections to the usefulness of the transform
remain - we do have the strlen pass that uses some global knowledge to decide
on profitability. One could argue that for -Os doing the reverse transform is
profitable?
Yes, match.pd doesn't support this (yet). It may be possible to teach it simple
cases like this - I plan to revisit this at some point. The issue is one of
side-effects which are tricky to handle if you consider patterns that do not
only match a single call (as this one would). So a baby-step towards getting
this supported in match.pd is to handle matching toplevel calls specially.
Richard.
> Wilco
>
>
> ChangeLog:
> 2016-04-19 Wilco Dijkstra <wdijk...@arm.com>
>
> gcc/
> * gcc/gimple-fold.c (gimple_fold_builtin_strchr):
> New function to optimize strchr (s, 0) to strlen.
> (gimple_fold_builtin): Add BUILT_IN_STRCHR case.
>
> testsuite/
> * gcc/testsuite/gcc.dg/strlenopt-20.c: Update test.
> * gcc/testsuite/gcc.dg/strlenopt-21.c: Likewise.
> * gcc/testsuite/gcc.dg/strlenopt-22.c: Likewise.
> * gcc/testsuite/gcc.dg/strlenopt-26.c: Likewise.
> * gcc/testsuite/gcc.dg/strlenopt-5.c: Likewise.
> * gcc/testsuite/gcc.dg/strlenopt-7.c: Likewise.
> * gcc/testsuite/gcc.dg/strlenopt-9.c: Likewise.
>
> --
>
> diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
> index
> eb130d048469f0b8196e565fed9a40de74b098bd..11dcf69fc919f066362f4f713db392d14b39764e
> 100644
> --- a/gcc/gimple-fold.c
> +++ b/gcc/gimple-fold.c
> @@ -1380,6 +1380,59 @@ gimple_fold_builtin_strncpy (gimple_stmt_iterator *gsi,
> return true;
> }
>
> +/* Simplify strchr (str, 0) into str + strlen (str).
> + In general strlen is significantly faster than strchr
> + due to being a simpler operation. */
> +static bool
> +gimple_fold_builtin_strchr (gimple_stmt_iterator *gsi)
> +{
> + gimple *stmt = gsi_stmt (*gsi);
> + tree str = gimple_call_arg (stmt, 0);
> + tree c = gimple_call_arg (stmt, 1);
> + location_t loc = gimple_location (stmt);
> +
> + if (optimize_function_for_size_p (cfun))
> + return false;
Hmm, I think we'd want a optimize_stmt_for_size_p (stmt) which
does the right thing for the case we have a CFG (look at the BB)
or when not (look at the function).
> + if (!integer_zerop (c) || !gimple_call_lhs (stmt))
> + return false;
> +
> + tree newstr;
> + tree strlen_fn = builtin_decl_implicit (BUILT_IN_STRLEN);
> +
> + if (!strlen_fn)
> + return false;
> +
> + /* Create newstr = strlen (str). */
> + gimple_seq stmts = NULL, stmts2;
> + gimple *repl = gimple_build_call (strlen_fn, 1, str);
> + gimple_set_location (repl, loc);
> + if (gimple_in_ssa_p (cfun))
> + newstr = make_ssa_name (size_type_node);
> + else
> + newstr = create_tmp_reg (size_type_node);
> + gimple_call_set_lhs (repl, newstr);
> + gimple_seq_add_stmt_without_update (&stmts, repl);
> +
> + /* Create (str p+ strlen (str)). */
> + newstr = fold_build_pointer_plus_loc (loc, str, newstr);
> + newstr = force_gimple_operand (newstr, &stmts2, true, NULL_TREE);
I think you want to build a gimple_assign directly here, otherwise ...
> + gimple_seq_add_seq_without_update (&stmts, stmts2);
> +
> + repl = gimple_build_assign (gimple_call_lhs (stmt), newstr);
> + gimple_seq_add_stmt_without_update (&stmts, repl);
> + gsi_replace_with_seq_vops (gsi, stmts);
> + /* gsi now points at the assignment to the lhs, get a
> + stmt iterator to the strlen.
> + ??? We can't use gsi_for_stmt as that doesn't work when the
> + CFG isn't built yet. */
> + gimple_stmt_iterator gsi2 = *gsi;
> + gsi_prev (&gsi2);
> + gsi_prev (&gsi2);
... this may not reliably end up at the call stmt.
> + fold_stmt (&gsi2);
> + return true;
> +}
> +
> /* Simplify a call to the strcat builtin. DST and SRC are the arguments
> to the call.
>
> @@ -2821,6 +2874,8 @@ gimple_fold_builtin (gimple_stmt_iterator *gsi)
> gimple_call_arg (stmt, 1));
> case BUILT_IN_STRNCAT:
> return gimple_fold_builtin_strncat (gsi);
> + case BUILT_IN_STRCHR:
> + return gimple_fold_builtin_strchr (gsi);
> case BUILT_IN_FPUTS:
> return gimple_fold_builtin_fputs (gsi, gimple_call_arg (stmt, 0),
> gimple_call_arg (stmt, 1), false);
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-20.c
> b/gcc/testsuite/gcc.dg/strlenopt-20.c
> index
> a83e845c26d88e5acdcabf142f7b319136663488..7b483eaeac1aa47278111a92148a16f00b2aaa2d
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-20.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-20.c
> @@ -86,9 +86,9 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 4 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-21.c
> b/gcc/testsuite/gcc.dg/strlenopt-21.c
> index
> e22fa9fca9ba14354db2cd5f602283b64bd8dcac..05b85a49dde0a7f5d269174fd4269e40be910dbd
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-21.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-21.c
> @@ -57,9 +57,9 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 3 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-22.c
> b/gcc/testsuite/gcc.dg/strlenopt-22.c
> index
> aa55f5ebd6a2d4803ee9a7fd60fc538d86f47124..b4ef772f0e59252f10a5419ede6837b3c8ca8265
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-22.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-22.c
> @@ -31,9 +31,9 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 3 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 4 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-26.c
> b/gcc/testsuite/gcc.dg/strlenopt-26.c
> index
> 4bd54bef540806ca90d2b9bcfc33eb531991c967..da2f465a5b5003fa5dca05f3a6ee00e97b98b5dd
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-26.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-26.c
> @@ -21,4 +21,5 @@ main (void)
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-5.c
> b/gcc/testsuite/gcc.dg/strlenopt-5.c
> index
> 1b006a93045599a75bdb10a39e86ffa59b475c83..a24aea44e8b00ff7b35a907aaa941b4c509642c4
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-5.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-5.c
> @@ -48,9 +48,9 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 2 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 2 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-7.c
> b/gcc/testsuite/gcc.dg/strlenopt-7.c
> index
> 3ae1e2cb3f0d08c8b05107c4e65b67bdb39cf7ab..aa53d7e75254dfe56c93172afc49f95e5b7901e6
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-7.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-7.c
> @@ -40,11 +40,11 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 2 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 1 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "\\*r_\[0-9\]* = 0;" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "return 3;" 1 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/strlenopt-9.c
> b/gcc/testsuite/gcc.dg/strlenopt-9.c
> index
> b0406b162d48fca375883035043b0c50b9db61a1..e5e276210ba4b7d75867605f1ecf5c06eb970ef5
> 100644
> --- a/gcc/testsuite/gcc.dg/strlenopt-9.c
> +++ b/gcc/testsuite/gcc.dg/strlenopt-9.c
> @@ -98,10 +98,10 @@ main ()
> return 0;
> }
>
> -/* { dg-final { scan-tree-dump-times "strlen \\(" 3 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strlen \\(" 5 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "memcpy \\(" 6 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcpy \\(" 1 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen" } } */
> -/* { dg-final { scan-tree-dump-times "strchr \\(" 3 "strlen" } } */
> +/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen" } } */
> /* { dg-final { scan-tree-dump-times "return 4;" 1 "optimized" } } */
>
