testsuite: Add new target check for no_alignment_constraints

A few testcases were marked for avr target, which has no alignment
requirements.  But those tests in fact should filter for any
target having __BIGGEST_ALIGNMENT__=1.

A new effective target check is introduced: no_alignment_constraints.
It checks whether __BIGGEST_ALIGNMENT__ is declared as 1.

This change fixes the testsuite cases for PRU target.

It was regression-tested on x86_64-pc-linux-gnu.

The following two existing macros were considered, but they check for
subtly different target behaviour:
 1. non_strict_align
    If true, non-aligned access is permitted. But it also allows
    variables to be naturally aligned, which is not true for
    no_alignment_constraints.

 2. default_packed
    Whether structures are packed by default is not necessarily
    the same as lacking constraints for non-aggregate types.
    For example, BIGGEST_FIELD_ALIGNMENT or ADJUST_FIELD_ALIGN
    could be defined for a target as something other than
    BIGGEST_ALIGNMENT.

gcc/ChangeLog:

	* doc/sourcebuild.texi: Document new no_alignment_constraints
	effective target check.

gcc/testsuite/ChangeLog:

	* c-c++-common/Wcast-align.c: Silence warnings for targets with
	no_alignment_constraints.
	* gcc.dg/c11-align-4.c: Skip for no_alignment_constraints.
	* gcc.dg/strlenopt-10.c: Replace checks for avr with checks for
	any target with no_alignment_constraints.
	* gcc.dg/strlenopt-11.c: Ditto.
	* gcc.dg/strlenopt-13.c: Ditto.
	* lib/target-supports.exp
	(check_effective_target_no_alignment_constraints): New.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>

1 files changed, 2 insertions, 2 deletions

diff --git a/gcc/testsuite/c-c++-common/Wcast-align.c b/gcc/testsuite/c-c++-common/Wcast-align.c
index c296c7f..1087b10 100644
--- a/gcc/testsuite/c-c++-common/Wcast-align.c
+++ b/gcc/testsuite/c-c++-common/Wcast-align.c
@@ -16,8 +16,8 @@ struct t { double x; } *q;
 void
 foo (void)
 {
-  y = (c *) x;  /* { dg-warning "7:cast \[^\n\r]* required alignment of target type" } */
-  z = (d *) x;  /* { dg-warning "7:cast \[^\n\r]* required alignment of target type" } */
+  y = (c *) x;  /* { dg-warning "7:cast \[^\n\r]* required alignment of target type" "" { target { ! no_alignment_constraints } } } */
+  z = (d *) x;  /* { dg-warning "7:cast \[^\n\r]* required alignment of target type" "" { target { ! no_alignment_constraints } } } */
   (long long *) p;  /* { dg-bogus "alignment" } */
   (double *) q;     /* { dg-bogus "alignment" } */
 }