------- Comment #31 from Joey dot ye at intel dot com 2009-02-23 03:15 -------
How about this patch?
1. Only reduce DI mode when -Os
2. Ignore TYPE_USER_ALIGN, so that stack realign happens for case in
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39137#c28, which IMHO is
acceptable.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 5221)
+++ config/i386/i386.c (working copy)
@@ -19607,6 +19607,13 @@
ix86_local_alignment (tree type, enum machine_mode mode,
unsigned int align)
{
+ /* We don't want to align DImode to 64bit for compilation with
+ -mpreferred-stack-boundary=2 to not enforce dynamic stack alignment
+ prologue. */
+ if (mode == DImode && !TARGET_64BIT && ix86_preferred_stack_boundary < 64
+ && optimize_function_for_size_p (cfun))
+ align = 32;
+
/* If TYPE is NULL, we are allocating a stack slot for caller-save
register in MODE. We will return the largest alignment of XF
and DF. */
@@ -19616,6 +19623,12 @@
align = GET_MODE_ALIGNMENT (DFmode);
return align;
}
+ if (!TARGET_64BIT
+ && optimize_function_for_size_p (cfun)
+ && align == 64
+ && ix86_preferred_stack_boundary < 64
+ && (mode == DImode || (type && TYPE_MODE (type) == DImode)))
+ align = 32;
/* x86-64 ABI requires arrays greater than 16 bytes to be aligned
to 16byte boundary. */
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39137
