[gcc(refs/vendors/vrull/heads/for-upstream)] Add new flag 'falign-arrays'

[Philipp Tomsich <ptomsich@gcc.gnu.org>]

https://gcc.gnu.org/g:19954801e11a8733d190ea5a03e65bc3c5c05f4f

commit 19954801e11a8733d190ea5a03e65bc3c5c05f4f
Author: Christoph Müllner <christoph.muellner@vrull.eu>
Date:   Fri Nov 11 17:28:42 2022 +0100

    Add new flag 'falign-arrays'
    
    This patch introduces a command line flag to define a minimum alignment
    for arrays. This allows to enable more and/or more efficient expansions
    of mem*/str* functions.
    
    Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

Diff:
---
 gcc/common.opt      | 3 +++
 gcc/doc/invoke.texi | 8 ++++++++
 gcc/stor-layout.cc  | 6 ++++++
 3 files changed, 17 insertions(+)

diff --git a/gcc/common.opt b/gcc/common.opt
index 26e9d1cc4e7..e25226e05df 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1017,6 +1017,9 @@ faggressive-loop-optimizations
 Common Var(flag_aggressive_loop_optimizations) Optimization Init(1)
 Aggressively optimize loops using language constraints.
 
+falign-arrays
+Common Var(flag_align_arrays) Optimization Init(0)
+
 falign-functions
 Common Var(flag_align_functions) Optimization
 Align the start of functions.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a4695454158..150c1dd395f 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -525,6 +525,7 @@ Objective-C and Objective-C++ Dialects}.
 @item Optimization Options
 @xref{Optimize Options,,Options that Control Optimization}.
 @gccoptlist{-faggressive-loop-optimizations @gol
+-falign-arrays @gol
 -falign-functions[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
 -falign-jumps[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
 -falign-labels[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
@@ -13386,6 +13387,13 @@ function boundary.
 The @option{-fipa-strict-aliasing} option is enabled by default and is
 effective only in combination with @option{-fstrict-aliasing}.
 
+@item -falign-arrays
+@opindex falign-arrays
+
+If this option is enabled, the compiler increases the minimum
+alignment of arrays to @code{STACK_BOUNDARY}, meaning the minimum
+alignment of the stack pointer is used.
+
 @item -falign-functions
 @itemx -falign-functions=@var{n}
 @itemx -falign-functions=@var{n}:@var{m}
diff --git a/gcc/stor-layout.cc b/gcc/stor-layout.cc
index 88923c4136b..c7ed706cd58 100644
--- a/gcc/stor-layout.cc
+++ b/gcc/stor-layout.cc
@@ -43,6 +43,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "attribs.h"
 #include "debug.h"
 #include "calls.h"
+#include "flags.h"
 
 /* Data type for the expressions representing sizes of data types.
    It is the first integer type laid out.  */
@@ -2567,6 +2568,11 @@ layout_type (tree type)
 	   using machine-dependent criteria if any.  */
 
 	unsigned align = TYPE_ALIGN (element);
+
+	/* Apply minimum alignment for arrays.  */
+	if (flag_align_arrays)
+	  align = MAX (align, STACK_BOUNDARY);
+
 	if (TYPE_USER_ALIGN (type))
 	  align = MAX (align, TYPE_ALIGN (type));
 	else