[PATCH] flag_complex_method: support optimize attribute

["Martin Liška" <mliska@suse.cz>]

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On 8/26/21 13:04, Richard Biener wrote:
> Yes, and that flag_complex_method is initialized via the langhook
> mentioned, for example
> c-family/c-opts.c has
> 
> /* Initialize options structure OPTS.  */
> void
> c_common_init_options_struct (struct gcc_options *opts)
> {
>    opts->x_flag_exceptions = c_dialect_cxx ();
>    opts->x_warn_pointer_arith = c_dialect_cxx ();
>    opts->x_warn_write_strings = c_dialect_cxx ();
>    opts->x_flag_warn_unused_result = true;
> 
>    /* By default, C99-like requirements for complex multiply and divide.  */
>    opts->x_flag_complex_method = 2;
> }
> 
> so an attempt to "cancel" a command-line option that adjusted any of
> the above will not
> work because we're not re-initializing global_options appropriately.
> But maybe we can
> just do that?  That is, call
> 
>    /* Initialize global options structures; this must be repeated for
>       each structure used for parsing options.  */
>    init_options_struct (&global_options, &global_options_set);
>    lang_hooks.init_options_struct (&global_options);
> 
> and
> 
>    /* Perform language-specific options initialization.  */
>    lang_hooks.init_options (save_decoded_options_count, save_decoded_options);
> 
> as done by toplev.c?  Or if we do not want to do that store that state away
> to an 'initialized_options/initialized_options_set' set of vars we can
> copy from?

Hello.

I think the proper fix is handling the flag_complex_method-related options in finish_options.
Doing that, we can see 'optimize' pragma works with the current master.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

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From 203451d5ea5352e75da27dcf8259cc8dd7880512 Mon Sep 17 00:00:00 2001
From: Martin Liska <mliska@suse.cz>
Date: Fri, 3 Sep 2021 10:53:00 +0200
Subject: [PATCH] flag_complex_method: support optimize attribute

gcc/ChangeLog:

	* opts.c (finish_options): Move flag_complex_method setting
	from ...
	* toplev.c (process_options): ... here.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/attr-complex-method.c: New test.
---
 gcc/opts.c                                             |  8 ++++++++
 .../gcc.c-torture/compile/attr-complex-method.c        | 10 ++++++++++
 gcc/toplev.c                                           |  8 --------
 3 files changed, 18 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/gcc.c-torture/compile/attr-complex-method.c

diff --git a/gcc/opts.c b/gcc/opts.c
index e0501551ef5..2ac1a932f38 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1323,6 +1323,14 @@ finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
       = (opts->x_flag_unroll_loops
          || opts->x_flag_peel_loops
          || opts->x_optimize >= 3);
+
+  /* With -fcx-limited-range, we do cheap and quick complex arithmetic.  */
+  if (opts->x_flag_cx_limited_range)
+    flag_complex_method = 0;
+
+  /* With -fcx-fortran-rules, we do something in-between cheap and C99.  */
+  if (opts->x_flag_cx_fortran_rules)
+    flag_complex_method = 1;
 }
 
 #define LEFT_COLUMN	27
diff --git a/gcc/testsuite/gcc.c-torture/compile/attr-complex-method.c b/gcc/testsuite/gcc.c-torture/compile/attr-complex-method.c
new file mode 100644
index 00000000000..f08b72e273f
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/attr-complex-method.c
@@ -0,0 +1,10 @@
+/* { dg-additional-options "-fdump-tree-optimized" } */
+
+#pragma GCC optimize "-fcx-limited-range"
+
+void do_div (_Complex double *a, _Complex double *b)
+{
+  *a = *b / (4.0 - 5.0fi);
+}
+
+/* { dg-final { scan-tree-dump-not "__divdc3" "optimized" } } */
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 14d1335e79e..e1688aae724 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1695,14 +1695,6 @@ process_options (void)
       flag_stack_check = NO_STACK_CHECK;
     }
 
-  /* With -fcx-limited-range, we do cheap and quick complex arithmetic.  */
-  if (flag_cx_limited_range)
-    flag_complex_method = 0;
-
-  /* With -fcx-fortran-rules, we do something in-between cheap and C99.  */
-  if (flag_cx_fortran_rules)
-    flag_complex_method = 1;
-
   /* Targets must be able to place spill slots at lower addresses.  If the
      target already uses a soft frame pointer, the transition is trivial.  */
   if (!FRAME_GROWS_DOWNWARD && flag_stack_protect)
-- 
2.33.0