hooks.h (hook_bool_mode_uhwi_false): Declare.

gcc/
	* hooks.h (hook_bool_mode_uhwi_false): Declare.
	* hooks.c (hook_bool_mode_uhwi_false): New function.
	* target.def (array_mode_supported_p): New hook.
	* doc/tm.texi.in (TARGET_ARRAY_MODE_SUPPORTED_P): Add @hook.
	* doc/tm.texi: Regenerate.
	* stor-layout.c (mode_for_array): New function.
	(layout_type): Use it.
	* config/arm/arm.c (arm_array_mode_supported_p): New function.
	(TARGET_ARRAY_MODE_SUPPORTED_P): Define.

From-SVN: r173290

2 files changed, 30 insertions, 0 deletions

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index a89d0ecc83d..7351e8338b8 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -4277,6 +4277,34 @@ insns involving vector mode @var{mode}.  At the very least, it
 must have move patterns for this mode.
 @end deftypefn
 
+@deftypefn {Target Hook} bool TARGET_ARRAY_MODE_SUPPORTED_P (enum machine_mode @var{mode}, unsigned HOST_WIDE_INT @var{nelems})
+Return true if GCC should try to use a scalar mode to store an array
+of @var{nelems} elements, given that each element has mode @var{mode}.
+Returning true here overrides the usual @code{MAX_FIXED_MODE} limit
+and allows GCC to use any defined integer mode.
+
+One use of this hook is to support vector load and store operations
+that operate on several homogeneous vectors.  For example, ARM NEON
+has operations like:
+
+@smallexample
+int8x8x3_t vld3_s8 (const int8_t *)
+@end smallexample
+
+where the return type is defined as:
+
+@smallexample
+typedef struct int8x8x3_t
+@{
+  int8x8_t val[3];
+@} int8x8x3_t;
+@end smallexample
+
+If this hook allows @code{val} to have a scalar mode, then
+@code{int8x8x3_t} can have the same mode.  GCC can then store
+@code{int8x8x3_t}s in registers rather than forcing them onto the stack.
+@end deftypefn
+
 @deftypefn {Target Hook} bool TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P (enum machine_mode @var{mode})
 Define this to return nonzero for machine modes for which the port has
 small register classes.  If this target hook returns nonzero for a given
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 4637088a819..45d5982eb7b 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4263,6 +4263,8 @@ insns involving vector mode @var{mode}.  At the very least, it
 must have move patterns for this mode.
 @end deftypefn
 
+@hook TARGET_ARRAY_MODE_SUPPORTED_P
+
 @hook TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P
 Define this to return nonzero for machine modes for which the port has
 small register classes.  If this target hook returns nonzero for a given