[PATCH ARM]: PR67745: Fix function alignment after __attribute__ 1/2

[Christian Bruel <christian.bruel@st.com>]

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This patch is the ARM part to make the function's alignment more
sensible to current function attributes that depends on both
opts->target_flags and opts->x_optimize_size.

- Does not change FUNCTION_BOUNDARY's value between functions for a
given ABI (arm or thumb). Setting done per function with override_options.

- Implements the TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE hook to track
aligns between functions.

No regressions for arm-none-eabi.

Christian


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2015-09-29  Christian Bruel  <christian.bruel@st.com>

	PR target/67745
	* config/arm/arm.h (FUNCTION_BOUNDARY): Move optimize_size condition to:
	* config/arm/arm.c (arm_option_override_internal): Call
	arm_override_options_after_change_1.
	(arm_override_options_after_change): New function.
	(arm_override_options_after_change_1): Likewise.
	(TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE): Define hook.

2015-09-29  Christian Bruel  <christian.bruel@st.com>

	PR target/67745
        * gcc.target/arm/attr-align1.c: New test.
        * gcc.target/arm/attr-align2.c: New test.
        * gcc.target/arm/attr-align3.c: New test.

Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c	(revision 228229)
+++ gcc/config/arm/arm.c	(working copy)
@@ -246,6 +246,7 @@ static tree arm_build_builtin_va_list (v
 static void arm_expand_builtin_va_start (tree, rtx);
 static tree arm_gimplify_va_arg_expr (tree, tree, gimple_seq *, gimple_seq *);
 static void arm_option_override (void);
+static void arm_override_options_after_change (void);
 static void arm_option_print (FILE *, int, struct cl_target_option *);
 static void arm_set_current_function (tree);
 static bool arm_can_inline_p (tree, tree);
@@ -407,6 +408,9 @@ static const struct attribute_spec arm_a
 #undef  TARGET_OPTION_OVERRIDE
 #define TARGET_OPTION_OVERRIDE arm_option_override
 
+#undef TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
+#define TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE arm_override_options_after_change
+
 #undef TARGET_OPTION_PRINT
 #define TARGET_OPTION_PRINT arm_option_print
 
@@ -2810,11 +2814,29 @@ static GTY(()) bool thumb_flipper;
 /* Options after initial target override.  */
 static GTY(()) tree init_optimize;
 
+static void
+arm_override_options_after_change_1 (struct gcc_options *opts)
+{
+  if (opts->x_align_functions <= 0)
+    opts->x_align_functions = TARGET_THUMB_P (opts->x_target_flags)
+      && opts->x_optimize_size ? 2 : 4;
+}
+
+/* Implement targetm.override_options_after_change.  */
+
+static void
+arm_override_options_after_change (void)
+{
+  arm_override_options_after_change_1 (&global_options);
+}
+
 /* Reset options between modes that the user has specified.  */
 static void
 arm_option_override_internal (struct gcc_options *opts,
 			      struct gcc_options *opts_set)
 {
+  arm_override_options_after_change_1 (opts);
+
   if (TARGET_THUMB_P (opts->x_target_flags)
       && !(ARM_FSET_HAS_CPU1 (insn_flags, FL_THUMB)))
     {
Index: gcc/config/arm/arm.h
===================================================================
--- gcc/config/arm/arm.h	(revision 228229)
+++ gcc/config/arm/arm.h	(working copy)
@@ -565,7 +565,7 @@ extern int arm_arch_crc;
 #define PREFERRED_STACK_BOUNDARY \
     (arm_abi == ARM_ABI_ATPCS ? 64 : STACK_BOUNDARY)
 
-#define FUNCTION_BOUNDARY  ((TARGET_THUMB && optimize_size) ? 16 : 32)
+#define FUNCTION_BOUNDARY           (TARGET_THUMB ? 16 : 32)
 
 /* The lowest bit is used to indicate Thumb-mode functions, so the
    vbit must go into the delta field of pointers to member
Index: gcc/testsuite/gcc.target/arm/attr-align1.c
===================================================================
--- gcc/testsuite/gcc.target/arm/attr-align1.c	(revision 0)
+++ gcc/testsuite/gcc.target/arm/attr-align1.c	(working copy)
@@ -0,0 +1,13 @@
+/* PR target/67745
+   Verify alignment when attribute target is used with -falign-functions.  */
+/* { dg-do compile } */
+/* { dg-options "-falign-functions=2" }  */
+
+/* Check that arm code is always 4 bytes aligned.  */
+void  __attribute__ ((target ("arm")))
+c(void)
+{
+}
+
+
+/* { dg-final { scan-assembler-not ".align\[ \t]*1" } } */
Index: gcc/testsuite/gcc.target/arm/attr-align2.c
===================================================================
--- gcc/testsuite/gcc.target/arm/attr-align2.c	(revision 0)
+++ gcc/testsuite/gcc.target/arm/attr-align2.c	(working copy)
@@ -0,0 +1,15 @@
+/* PR target/67745
+   Verify alignment when attribute optimize is used.  */
+/* { dg-do compile } */
+/* { dg-skip-if "" { ! { arm_thumb1_ok || arm_thumb2_ok } } } */
+/* { dg-options "-O2 -mthumb" }  */
+
+/* Check that thumb code is always 2 bytes aligned for -Os.  */
+
+void
+__attribute__ ((optimize("Os")))
+foo()
+{
+}
+
+/* { dg-final { scan-assembler ".align\[ \t]*1" } } */
Index: gcc/testsuite/gcc.target/arm/attr-align3.c
===================================================================
--- gcc/testsuite/gcc.target/arm/attr-align3.c	(revision 0)
+++ gcc/testsuite/gcc.target/arm/attr-align3.c	(working copy)
@@ -0,0 +1,13 @@
+/* PR target/67745
+   Verify alignment when attribute target is used.  */
+/* { dg-do compile } */
+/* { dg-skip-if "" { ! { arm_thumb1_ok || arm_thumb2_ok } } } */
+/* { dg-options "-Os -mthumb" }  */
+
+/* Check that thumb code is always 4 bytes aligned.  */
+void  __attribute__ ((target ("arm")))
+c(void)
+{
+}
+
+/* { dg-final { scan-assembler-not ".align\[ \t]*1" } } */