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>

7 files changed, 43 insertions, 21 deletions

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index 3696a58..760ff95 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2716,6 +2716,7 @@ Target supports @option{-branch-cost=N}.
 Target uses @code{__cxa_atexit}.
 
 @item default_packed
+@anchor{default_packed}
 Target has packed layout of structure members by default.
 
 @item exceptions
@@ -2786,6 +2787,14 @@ Target uses natural alignment (aligned to type size) for types of
 Target uses natural alignment (aligned to type size) for types of
 64 bits or less.
 
+@item no_alignment_constraints
+Target defines __BIGGEST_ALIGNMENT__=1.  Hence target imposes
+no alignment constraints.  This is similar, but not necessarily
+the same as @ref{default_packed}.  Although @code{BIGGEST_FIELD_ALIGNMENT}
+defaults to @code{BIGGEST_ALIGNMENT} for most targets, it is possible
+for a target to set those two with different values and have different
+alignment constraints for aggregate and non-aggregate types.
+
 @item noinit
 Target supports the @code{noinit} variable attribute.
 
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" } */
 }
diff --git a/gcc/testsuite/gcc.dg/c11-align-4.c b/gcc/testsuite/gcc.dg/c11-align-4.c
index 57f93ff..eb9071b 100644
--- a/gcc/testsuite/gcc.dg/c11-align-4.c
+++ b/gcc/testsuite/gcc.dg/c11-align-4.c
@@ -2,7 +2,7 @@
    are at least some alignment constraints).  */
 /* { dg-do compile } */
 /* { dg-options "-std=c11 -pedantic-errors" } */
-/* { dg-skip-if "no alignment constraints" { "avr-*-*" } } */
+/* { dg-skip-if "no alignment constraints" { no_alignment_constraints } } */
 
 #include <stddef.h>
 
diff --git a/gcc/testsuite/gcc.dg/strlenopt-10.c b/gcc/testsuite/gcc.dg/strlenopt-10.c
index ce959c3..6e2c259 100644
--- a/gcc/testsuite/gcc.dg/strlenopt-10.c
+++ b/gcc/testsuite/gcc.dg/strlenopt-10.c
@@ -70,10 +70,10 @@ main ()
 }
 
 /* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen1" } } */
-/* avr has BIGGEST_ALIGNMENT 8, allowing fold_builtin_memory_op
+/* Some targets have BIGGEST_ALIGNMENT 8-bits, allowing fold_builtin_memory_op
    to expand the memcpy call at the end of fn2.  */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 8 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { avr-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 8 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { no_alignment_constraints} } } } */
 /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen1" } } */
diff --git a/gcc/testsuite/gcc.dg/strlenopt-11.c b/gcc/testsuite/gcc.dg/strlenopt-11.c
index abd9fae..952de07 100644
--- a/gcc/testsuite/gcc.dg/strlenopt-11.c
+++ b/gcc/testsuite/gcc.dg/strlenopt-11.c
@@ -59,17 +59,17 @@ main ()
 }
 
 /* { dg-final { scan-tree-dump-times "strlen \\(" 3 "strlen1" } } */
-/* avr has BIGGEST_ALIGNMENT 8, allowing fold_builtin_memory_op
+/* Some targets have BIGGEST_ALIGNMENT 8-bits, allowing fold_builtin_memory_op
    to expand the memcpy call at the end of fn1.  */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 6 "strlen1" { target { avr-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 6 "strlen1" { target { no_alignment_constraints } } } } */
 /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen1" } } */
 /* Where the memcpy is expanded, the assignemts to elements of l are
    propagated.  */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.0. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.6. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.9. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;" 3 "strlen1" { target { avr-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.0. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.6. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.9. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;" 3 "strlen1" { target { no_alignment_constraints } } } } */
diff --git a/gcc/testsuite/gcc.dg/strlenopt-13.c b/gcc/testsuite/gcc.dg/strlenopt-13.c
index 27ecc79..4c6d526 100644
--- a/gcc/testsuite/gcc.dg/strlenopt-13.c
+++ b/gcc/testsuite/gcc.dg/strlenopt-13.c
@@ -56,18 +56,18 @@ main ()
 }
 
 /* { dg-final { scan-tree-dump-times "strlen \\(" 4 "strlen1" } } */
-/* avr has BIGGEST_ALIGNMENT 8, allowing fold_builtin_memory_op
+/* Some targets have BIGGEST_ALIGNMENT 8-bits, allowing fold_builtin_memory_op
    to expand the memcpy call at the end of fn1.  */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "memcpy \\(" 6 "strlen1" { target { avr-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 7 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "memcpy \\(" 6 "strlen1" { target { no_alignment_constraints } } } } */
 /* { dg-final { scan-tree-dump-times "strcpy \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strcat \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen1" } } */
 /* { dg-final { scan-tree-dump-times "stpcpy \\(" 0 "strlen1" } } */
 /* Where the memcpy is expanded, the assignemts to elements of l are
    propagated.  */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.0. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.1. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.5. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.6. = " 1 "strlen1" { target { ! avr-*-* } } } } */
-/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;" 4 "strlen1" { target { avr-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.0. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.1. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.5. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;\[\n\r\]*  l.6. = " 1 "strlen1" { target { ! no_alignment_constraints } } } } */
+/* { dg-final { scan-tree-dump-times "  _\[0-9\]* = strlen \\(\[^\n\r\]*;" 4 "strlen1" { target { no_alignment_constraints } } } } */
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index e481a2a..48c5dda 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -7549,6 +7549,19 @@ proc check_effective_target_vect_aligned_arrays { } {
     return $et_vect_aligned_arrays
 }
 
+# Return 1 if the biggest alignment required by target is 1 * BITS_PER_UNIT.
+# In such case the target does not impose any alignment constraints.
+
+proc check_effective_target_no_alignment_constraints { } {
+    return [check_runtime_nocache no_alignment_constraints {
+        int
+        main (void)
+        {
+          return __BIGGEST_ALIGNMENT__ == 1 ? 0 : 1;
+        }
+    }]
+}
+
 # Return 1 if types of size 32 bit or less are naturally aligned
 # (aligned to their type-size), 0 otherwise.
 #