Re: [PATCH, S390] Increase function alignment to 16 bytes

[Robin Dapp <rdapp at linux dot ibm dot com>]

Hi,

> Please skip '+      && !opts->x_optimize_size)'. I'm attaching patch
> that will
> set opts->x_flag_align_functions to 0 for -Os. It's part of another batch
> alignment patches I'm preparing.

done in the attached version and added some tests (which do not all fail
without the patch as we can get lucky with the alignment).

Regtested on s390x.

Regards
 Robin

--

gcc/ChangeLog:

2018-07-12  Robin Dapp  <rdapp@linux.ibm.com>

	* config/s390/s390.c (s390_default_align): Set default function
	alignment to 16.
	(s390_override_options_after_change): Call s390_default align.
	(s390_option_override_internal): Call s390_default_align.
	(TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE): Define.

gcc/testsuite/ChangeLog:

2018-07-12  Robin Dapp  <rdapp@linux.ibm.com>

	* gcc.target/s390/function-align1.c: New test.
	* gcc.target/s390/function-align2.c: New test.
	* gcc.target/s390/function-align3.c: New test.

diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index 8df195ddd78..af4cc702259 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -15322,6 +15322,22 @@ s390_function_specific_restore (struct gcc_options *opts,
   opts->x_s390_cost_pointer = (long)processor_table[opts->x_s390_tune].cost;
 }
 
+static void
+s390_default_align (struct gcc_options *opts)
+{
+  /* Set the default function alignment to 16 in order to get rid of
+     some unwanted performance effects. */
+  if (opts->x_flag_align_functions && !opts->x_str_align_functions
+      && opts->x_s390_tune >= PROCESSOR_2964_Z13)
+    opts->x_str_align_functions = "16";
+}
+
+static void
+s390_override_options_after_change (void)
+{
+  s390_default_align (&global_options);
+}
+
 static void
 s390_option_override_internal (bool main_args_p,
 			       struct gcc_options *opts,
@@ -15559,6 +15575,9 @@ s390_option_override_internal (bool main_args_p,
 			 opts->x_param_values,
 			 opts_set->x_param_values);
 
+  /* Set the default alignment.  */
+  s390_default_align (opts);
+
   /* Call target specific restore function to do post-init work.  At the moment,
      this just sets opts->x_s390_cost_pointer.  */
   s390_function_specific_restore (opts, NULL);
@@ -16751,6 +16770,9 @@ s390_case_values_threshold (void)
 #undef TARGET_PASS_BY_REFERENCE
 #define TARGET_PASS_BY_REFERENCE s390_pass_by_reference
 
+#undef  TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
+#define TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE s390_override_options_after_change
+
 #undef TARGET_FUNCTION_OK_FOR_SIBCALL
 #define TARGET_FUNCTION_OK_FOR_SIBCALL s390_function_ok_for_sibcall
 #undef TARGET_FUNCTION_ARG
diff --git a/gcc/testsuite/gcc.target/s390/function-align1.c b/gcc/testsuite/gcc.target/s390/function-align1.c
new file mode 100644
index 00000000000..78fa563098e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/function-align1.c
@@ -0,0 +1,24 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -march=z13"  } */
+
+#include <assert.h>
+#include <stdint.h>
+
+__attribute__((noinline))
+void foo1 () {}
+
+__attribute__((noinline))
+__attribute__((optimize("align-functions=32")))
+void foo2 () {}
+
+int main ()
+{
+  foo1 ();
+  foo2 ();
+
+  void *f = &foo1;
+  void *g = &foo2;
+
+  assert (((uintptr_t)f % 16) == 0);
+  assert (((uintptr_t)g % 32) == 0);
+}
diff --git a/gcc/testsuite/gcc.target/s390/function-align2.c b/gcc/testsuite/gcc.target/s390/function-align2.c
new file mode 100644
index 00000000000..0d8e1ff2251
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/function-align2.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-Os -march=z13"  } */
+
+void bar ()
+{
+  /* { dg-final { scan-assembler-times ".align\t8" 2 } } */
+}
+
+__attribute__((optimize("O2")))
+void baz ()
+{
+  /* { dg-final { scan-assembler-times ".align\t16" 1 } } */
+}
diff --git a/gcc/testsuite/gcc.target/s390/function-align3.c b/gcc/testsuite/gcc.target/s390/function-align3.c
new file mode 100644
index 00000000000..adb79763d4a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/function-align3.c
@@ -0,0 +1,22 @@
+/* { dg-do run } */
+/* { dg-options "-Os -march=z13"  } */
+
+#include <assert.h>
+#include <stdint.h>
+
+__attribute__((noinline))
+void bar () {}
+
+__attribute__((noinline))
+__attribute__((optimize("O2")))
+void baf () {}
+
+int main ()
+{
+  bar ();
+  baf ();
+
+  void *g = &baf;
+
+  assert ( ((uintptr_t)g % 16) == 0);
+}