Hi,
this patch removes flag_strict_aliasing kludge in expanding debug locations and
instead it introduces explicit parameter DEBUG that makes
set_mem_attributes_minus_bitpos to not affect alias sets. This is sanity
checked by comparing number of alias sets before and after at a time we
originally overwritten flag_strict_aliasing.
I also added code to prevent memory attributes creation for !optimize and to
avoid get_alias_set computation for !flag_strict_aliasing. This slightly
optimizes -O0 builds but the results seems to be down in the noise (I would not
object to leave it out).
The patch should fix at least one (latent?) bug that call_stmt expansion
invoke expand_debug_expr without clearing flag_strict_aliasing.
Bootstrapped/regtested x86_64-linux, also tested with compare-debug, OK?
Honza
* cfgexpand.c: Include alias.h
(expand_debug_expr): Pass debug=true to set_mem_attributes.
(expand_debug_locations): Do not fiddle with flag_strict_aliasing;
sanity check that no new alias set was introduced.
* varasm.c: Include alias.h
(make_decl_rtl): New parameter DEBUG; pass it to set_mem_attributes.
(make_decl_rtl_for_debug): Do ont fiddle with flag_strict_aliasing;
assert that no new alias set was introduced.
* varasm.h (make_decl_rtl): New parameter debug.
* alias.h (num_alias_sets): New function.
* emit-rtl.c (set_mem_attributes_minus_bitpos): New parameter DEBUG;
exit early when not optimizing; do not introduce new alias set when
producing debug only attributes.
(set_mem_attributes): New parameter DEBUG.
* emit-rtl.h (set_mem_attributes, set_mem_attributes_minus_bitpos):
New parameters DEBUG.
(num_alias_sets): New function.
Index: cfgexpand.c
===================================================================
--- cfgexpand.c (revision 231122)
+++ cfgexpand.c (working copy)
@@ -73,6 +73,7 @@ along with GCC; see the file COPYING3.
#include "builtins.h"
#include "tree-chkp.h"
#include "rtl-chkp.h"
+#include "alias.h"
/* Some systems use __main in a way incompatible with its use in gcc, in these
cases use the macros NAME__MAIN to give a quoted symbol and SYMBOL__MAIN to
@@ -4178,7 +4179,7 @@ expand_debug_expr (tree exp)
return NULL_RTX;
op0 = gen_rtx_CONST_STRING (Pmode, TREE_STRING_POINTER (exp));
op0 = gen_rtx_MEM (BLKmode, op0);
- set_mem_attributes (op0, exp, 0);
+ set_mem_attributes (op0, exp, 0, true);
return op0;
}
/* Fall through... */
@@ -4346,7 +4347,7 @@ expand_debug_expr (tree exp)
return NULL;
op0 = gen_rtx_MEM (mode, op0);
- set_mem_attributes (op0, exp, 0);
+ set_mem_attributes (op0, exp, 0, true);
if (TREE_CODE (exp) == MEM_REF
&& !is_gimple_mem_ref_addr (TREE_OPERAND (exp, 0)))
set_mem_expr (op0, NULL_TREE);
@@ -4372,7 +4373,7 @@ expand_debug_expr (tree exp)
op0 = gen_rtx_MEM (mode, op0);
- set_mem_attributes (op0, exp, 0);
+ set_mem_attributes (op0, exp, 0, true);
set_mem_addr_space (op0, as);
return op0;
@@ -4458,7 +4459,7 @@ expand_debug_expr (tree exp)
op0 = copy_rtx (op0);
if (op0 == orig_op0)
op0 = shallow_copy_rtx (op0);
- set_mem_attributes (op0, exp, 0);
+ set_mem_attributes (op0, exp, 0, true);
}
if (bitpos == 0 && mode == GET_MODE (op0))
@@ -5219,12 +5220,11 @@ expand_debug_locations (void)
{
rtx_insn *insn;
rtx_insn *last = get_last_insn ();
- int save_strict_alias = flag_strict_aliasing;
/* New alias sets while setting up memory attributes cause
-fcompare-debug failures, even though it doesn't bring about any
codegen changes. */
- flag_strict_aliasing = 0;
+ int num = num_alias_sets ();
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
if (DEBUG_INSN_P (insn))
@@ -5284,7 +5284,7 @@ expand_debug_locations (void)
avoid_complex_debug_insns (insn2, &INSN_VAR_LOCATION_LOC (insn2), 0);
}
- flag_strict_aliasing = save_strict_alias;
+ gcc_checking_assert (num == num_alias_sets ());
}
/* Performs swapping operands of commutative operations to expand
Index: varasm.c
===================================================================
--- varasm.c (revision 231122)
+++ varasm.c (working copy)
@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.
#include "common/common-target.h"
#include "asan.h"
#include "rtl-iter.h"
+#include "alias.h"
#ifdef XCOFF_DEBUGGING_INFO
#include "xcoffout.h" /* Needed for external data declarations. */
@@ -1280,7 +1281,7 @@ ultimate_transparent_alias_target (tree
This is never called for PARM_DECL nodes. */
void
-make_decl_rtl (tree decl)
+make_decl_rtl (tree decl, bool debug)
{
const char *name = 0;
int reg_number;
@@ -1470,7 +1471,7 @@ make_decl_rtl (tree decl)
x = gen_rtx_MEM (DECL_MODE (decl), x);
if (TREE_CODE (decl) != FUNCTION_DECL)
- set_mem_attributes (x, decl, 1);
+ set_mem_attributes (x, decl, 1, debug);
SET_DECL_RTL (decl, x);
/* Optionally set flags or add text to the name to record information
@@ -1487,27 +1488,25 @@ make_decl_rtl (tree decl)
rtx
make_decl_rtl_for_debug (tree decl)
{
- unsigned int save_aliasing_flag;
rtx rtl;
if (DECL_RTL_SET_P (decl))
return DECL_RTL (decl);
- /* Kludge alert! Somewhere down the call chain, make_decl_rtl will
- call new_alias_set. If running with -fcompare-debug, sometimes
- we do not want to create alias sets that will throw the alias
- numbers off in the comparison dumps. So... clearing
- flag_strict_aliasing will keep new_alias_set() from creating a
- new set. */
- save_aliasing_flag = flag_strict_aliasing;
- flag_strict_aliasing = 0;
+ int num = num_alias_sets ();
+ make_decl_rtl (decl, true);
rtl = DECL_RTL (decl);
/* Reset DECL_RTL back, as various parts of the compiler expects
DECL_RTL set meaning it is actually going to be output. */
SET_DECL_RTL (decl, NULL);
+
+ /* Be sure that make_decl_rtl will not cal lnew_alias set.
+ If running with -fcompare-debug, sometimes
+ we do not want to create alias sets that will throw the alias
+ numbers off in the comparison dumps. */
+ gcc_checking_assert (num == num_alias_sets ());
- flag_strict_aliasing = save_aliasing_flag;
return rtl;
}
Index: varasm.h
===================================================================
--- varasm.h (revision 231122)
+++ varasm.h (working copy)
@@ -28,7 +28,7 @@ along with GCC; see the file COPYING3.
extern tree cold_function_name;
extern tree tree_output_constant_def (tree);
-extern void make_decl_rtl (tree);
+extern void make_decl_rtl (tree, bool debug = false);
extern rtx make_decl_rtl_for_debug (tree);
extern void make_decl_one_only (tree, tree);
extern int supports_one_only (void);
Index: alias.h
===================================================================
--- alias.h (revision 231122)
+++ alias.h (working copy)
@@ -25,6 +25,7 @@ extern alias_set_type get_alias_set (tre
extern alias_set_type get_deref_alias_set (tree);
extern alias_set_type get_varargs_alias_set (void);
extern alias_set_type get_frame_alias_set (void);
+extern int num_alias_sets (void);
extern tree component_uses_parent_alias_set_from (const_tree);
extern bool alias_set_subset_of (alias_set_type, alias_set_type);
extern void record_alias_subset (alias_set_type, alias_set_type);
Index: emit-rtl.c
===================================================================
--- emit-rtl.c (revision 231122)
+++ emit-rtl.c (working copy)
@@ -1738,16 +1738,20 @@ get_mem_align_offset (rtx mem, unsigned
/* Given REF (a MEM) and T, either the type of X or the expression
corresponding to REF, set the memory attributes. OBJECTP is nonzero
if we are making a new object of this type. BITPOS is nonzero if
- there is an offset outstanding on T that will be applied later. */
+ there is an offset outstanding on T that will be applied later.
+ if DEBUG is true, assume that the MEM will be used only for debug
+ insns. */
void
set_mem_attributes_minus_bitpos (rtx ref, tree t, int objectp,
- HOST_WIDE_INT bitpos)
+ HOST_WIDE_INT bitpos, bool debug)
{
HOST_WIDE_INT apply_bitpos = 0;
tree type;
struct mem_attrs attrs, *defattrs, *refattrs;
addr_space_t as;
+ bool global_var = false;
+ tree orig_t = t;
/* It can happen that type_for_mode was given a mode for which there
is no language-level type. In which case it returns NULL, which
@@ -1759,18 +1763,8 @@ set_mem_attributes_minus_bitpos (rtx ref
if (type == error_mark_node)
return;
- /* If we have already set DECL_RTL = ref, get_alias_set will get the
- wrong answer, as it assumes that DECL_RTL already has the right alias
- info. Callers should not set DECL_RTL until after the call to
- set_mem_attributes. */
- gcc_assert (!DECL_P (t) || ref != DECL_RTL_IF_SET (t));
-
memset (&attrs, 0, sizeof (attrs));
- /* Get the alias set from the expression or type (perhaps using a
- front-end routine) and use it. */
- attrs.alias = get_alias_set (t);
-
MEM_VOLATILE_P (ref) |= TYPE_VOLATILE (type);
MEM_POINTER (ref) = POINTER_TYPE_P (type);
@@ -1829,6 +1823,12 @@ set_mem_attributes_minus_bitpos (rtx ref
{
tree base;
+ if (TREE_CODE (t) == CONST_DECL
+ || (TREE_CODE (t) == VAR_DECL
+ && auto_var_in_fn_p (t, current_function_decl))
+ || (TREE_CODE (t) == LABEL_DECL && DECL_NONLOCAL (t)))
+ global_var = true;
+
if (TREE_THIS_VOLATILE (t))
MEM_VOLATILE_P (ref) = 1;
@@ -1866,13 +1866,20 @@ set_mem_attributes_minus_bitpos (rtx ref
as = TYPE_ADDR_SPACE (TREE_TYPE (base));
}
+ /* When not optimizing, there is no need to attach memory attributes
+ unless we produce DECL_RTL of declaration that may later be used in a
+ function that is optimized. */
+ if (!optimize && !global_var)
+ return;
+
/* If this expression uses it's parent's alias set, mark it such
that we won't change it. */
- if (component_uses_parent_alias_set_from (t) != NULL_TREE)
+ if (!debug && (flag_strict_aliasing || global_var)
+ && component_uses_parent_alias_set_from (t) != NULL_TREE)
MEM_KEEP_ALIAS_SET_P (ref) = 1;
/* If this is a decl, set the attributes of the MEM from it. */
- if (DECL_P (t))
+ else if (DECL_P (t))
{
attrs.expr = t;
attrs.offset_known_p = true;
@@ -1962,6 +1969,11 @@ set_mem_attributes_minus_bitpos (rtx ref
obj_align = (obj_bitpos & -obj_bitpos);
attrs.align = MAX (attrs.align, obj_align);
}
+ /* When not optimizing, there is no need to attach memory attributes
+ unless we produce DECL_RTL of declaration that may later be used in a
+ function that is optimized. */
+ else if (!global_var && !optimize)
+ return;
if (tree_fits_uhwi_p (new_size))
{
@@ -1980,15 +1992,29 @@ set_mem_attributes_minus_bitpos (rtx ref
attrs.size += apply_bitpos / BITS_PER_UNIT;
}
+ /* Get the alias set from the expression or type (perhaps using a
+ front-end routine) and use it. Never produce new alias sets when
+ the memory reference is used only for debug (so the alias numbers
+ are stable) and with !flag_strict_aliasing for all function local RTLs.
*/
+ if (!debug && (flag_strict_aliasing || global_var))
+ {
+ /* If we have already set DECL_RTL = ref, get_alias_set will get the
+ wrong answer, as it assumes that DECL_RTL already has the right alias
+ info. Callers should not set DECL_RTL until after the call to
+ set_mem_attributes. */
+ gcc_assert (!DECL_P (orig_t) || ref != DECL_RTL_IF_SET (orig_t));
+ attrs.alias = get_alias_set (orig_t);
+ }
+
/* Now set the attributes we computed above. */
attrs.addrspace = as;
set_mem_attrs (ref, &attrs);
}
void
-set_mem_attributes (rtx ref, tree t, int objectp)
+set_mem_attributes (rtx ref, tree t, int objectp, bool debug)
{
- set_mem_attributes_minus_bitpos (ref, t, objectp, 0);
+ set_mem_attributes_minus_bitpos (ref, t, objectp, 0, debug);
}
/* Set the alias set of MEM to SET. */
Index: emit-rtl.h
===================================================================
--- emit-rtl.h (revision 231122)
+++ emit-rtl.h (working copy)
@@ -484,13 +484,16 @@ extern rtx offset_address (rtx, rtx, uns
/* Given REF, a MEM, and T, either the type of X or the expression
corresponding to REF, set the memory attributes. OBJECTP is nonzero
- if we are making a new object of this type. */
-extern void set_mem_attributes (rtx, tree, int);
+ if we are making a new object of this type.
+ If DEBUG is true, the memory expression will be used only for debug
+ statements and in that case avoid creation of new alias set. */
+extern void set_mem_attributes (rtx, tree, int, bool debug = false);
/* Similar, except that BITPOS has not yet been applied to REF, so if
we alter MEM_OFFSET according to T then we should subtract BITPOS
expecting that it'll be added back in later. */
-extern void set_mem_attributes_minus_bitpos (rtx, tree, int, HOST_WIDE_INT);
+extern void set_mem_attributes_minus_bitpos (rtx, tree, int, HOST_WIDE_INT,
+ bool debug = false);
/* Return OFFSET if XEXP (MEM, 0) - OFFSET is known to be ALIGN
bits aligned for 0 <= OFFSET < ALIGN / BITS_PER_UNIT, or
Index: alias.c
===================================================================
--- alias.c (revision 231146)
+++ alias.c (working copy)
@@ -1096,6 +1096,17 @@ new_alias_set (void)
return 0;
}
+/* Return number of alias sets; used for sanity checking that we did not
+ introduced new ones for debug statements. */
+
+int
+num_alias_sets (void)
+{
+ if (!alias_sets)
+ return 0;
+ return alias_sets->length ();
+}
+
/* Indicate that things in SUBSET can alias things in SUPERSET, but that
not everything that aliases SUPERSET also aliases SUBSET. For example,
in C, a store to an `int' can alias a load of a structure containing an
