On Thu, Aug 06, 2009 at 02:42:16PM -0700, H.J. Lu wrote:
Hi,
In 32bit, the incoming stack may not be 16 byte aligned. This patch
assumes the incoming stack is 4 byte aligned and realigns stack if any
SSE variable is put on stack. Any comments?
For i386, gcc, up to gcc 3.4, had been generating 4byte stack alignment.
4byte stack alignment is a problem unless SSE registers are used, which
may be generated by vectorizer or intrinsics. This patch accommodates
the binaries generated by previous versions of gcc if SSE registers are
generated by vectorizer or intrinsics. The performance impact on SPEC
CPU 2006 is minimum:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156#c7
OK for trunk?
---
gcc/
2009-09-26 H.J. Lu<hongjiu.lu@intel.com>
PR target/40838
* function.c (allocate_struct_function): Initialize
forced_stack_alignment and forced_stack_mode.
* function.h (function): Add forced_stack_alignment and
forced_stack_mode.
* tree-vect-data-refs.c (vect_verify_datarefs_alignment):
Update forced_stack_alignment and forced_stack_mode.
* config/i386/i386.c (VALID_SSE_VECTOR_MODE): New.
(ix86_update_stack_boundary): In 32bit, use STACK_BOUNDARY if
any SSE variables are forced on stack.
(ix86_minimum_alignment): In 32bit, update
forced_stack_alignment and forced_stack_mode if any SSE
variables are put on stack.
gcc/testsuite/
Index: gcc/function.h
===================================================================
--- gcc/function.h (revision 152202)
+++ gcc/function.h (working copy)
@@ -532,6 +532,12 @@ struct GTY(()) function {
a string describing the reason for failure. */
const char * GTY((skip)) cannot_be_copied_reason;
+ /* The largest alignment forced on the stack. */
+ unsigned int forced_stack_alignment;
+
+ /* The mode of the largest alignment forced on the stack. */
+ enum machine_mode forced_stack_mode;
+
/* Collected bit flags. */
/* Number of units of general registers that need saving in stdarg
Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c (revision 152202)
+++ gcc/tree-vect-data-refs.c (working copy)
@@ -927,6 +927,8 @@ vect_verify_datarefs_alignment (loop_vec
{
gimple stmt = DR_STMT (dr);
stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
+ enum machine_mode mode;
+ unsigned int align;
/* For interleaving, only the alignment of the first access matters. */
if (STMT_VINFO_STRIDED_ACCESS (stmt_info)
@@ -947,6 +949,15 @@ vect_verify_datarefs_alignment (loop_vec
}
return false;
}
+
+ mode = TYPE_MODE (STMT_VINFO_VECTYPE (stmt_info));
+ align = GET_MODE_ALIGNMENT (mode);
+ if (cfun->forced_stack_alignment< align)
+ {
+ cfun->forced_stack_alignment = align;
+ cfun->forced_stack_mode = mode;
+ }
+
if (supportable_dr_alignment != dr_aligned
&& vect_print_dump_info (REPORT_ALIGNMENT))
fprintf (vect_dump, "Vectorizing an unaligned access.");
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 152202)
+++ gcc/config/i386/i386.c (working copy)
@@ -8151,16 +8151,31 @@ find_drap_reg (void)
}
}
+#define VALID_SSE_VECTOR_MODE(MODE) \
+ ((MODE) == V4SFmode || (MODE) == V4SImode || (MODE) == V2DFmode \
+ || (MODE) == V16QImode || (MODE) == V8HImode || (MODE) == V2DImode)
+
/* Update incoming stack boundary and estimated stack alignment. */
static void
ix86_update_stack_boundary (void)
{
+ /* Should we use STACK_BOUNDARY for incoming stack boundary? */
+ unsigned int incoming_stack_boundary;
+
+ /* In 32bit, use STACK_BOUNDARY for incoming stack boundary if any
+ SSE variables are put on stack. */
+ if (!TARGET_64BIT
+&& VALID_SSE_VECTOR_MODE (cfun->forced_stack_mode))
+ incoming_stack_boundary = STACK_BOUNDARY;
+ else
+ incoming_stack_boundary = ix86_default_incoming_stack_boundary;
+
/* Prefer the one specified at command line. */
ix86_incoming_stack_boundary
= (ix86_user_incoming_stack_boundary
? ix86_user_incoming_stack_boundary
- : ix86_default_incoming_stack_boundary);
+ : incoming_stack_boundary);
/* Incoming stack alignment can be changed on individual functions
via force_align_arg_pointer attribute. We use the smallest
@@ -19773,7 +19788,7 @@ ix86_minimum_alignment (tree exp, enum m
{
tree type, decl;
- if (TARGET_64BIT || align != 64 || ix86_preferred_stack_boundary>= 64)
+ if (TARGET_64BIT)
return align;
if (exp&& DECL_P (exp))
@@ -19787,6 +19802,25 @@ ix86_minimum_alignment (tree exp, enum m
decl = NULL;
}
+ /* In 32bit, update forced_stack_mode if any SSE variables are put
+ on stack. */
+ if (cfun->forced_stack_alignment< 128)
+ {
+ if (VALID_SSE_VECTOR_MODE (mode))
+ {
+ cfun->forced_stack_alignment = 128;
+ cfun->forced_stack_mode = mode;
+ }
+ else if ((type&& VALID_SSE_VECTOR_MODE (TYPE_MODE (type))))
+ {
+ cfun->forced_stack_alignment = 128;
+ cfun->forced_stack_mode = TYPE_MODE (type);
+ }
+ }
+
+ if (align != 64 || ix86_preferred_stack_boundary>= 64)
+ return align;
+