Hi,
this is the last patch of the series. It makes operand_equal_p to compare
alias sets even in !flag_strict_aliasing before inlining so inlining
!flag_strict_aliasing to flag_strict_aliasing is possible when callee is
merged comdat. I tried to explain it in greater detail in the comment
in ipa-inline-tranform.
While working on the code I noticed that I managed to overload merged with
two meanings. One is that the function had bodies defined in multiple units
(and thus its inlining should not be considered cross-modulo) and other is
that it used to be comdat. This is usually the same, but not always - one
can manually define weak functions where the bypass for OPTIMIZAITON_NODE
checks can not apply.
Since the first only affects heuristics and I do not think I need to care
about weaks much, I dropped it and renamed the flag to merged_comdat to make
it more obvious what it means.
Bootstrapped/regtested x86_64-linux, OK?
I will work on some testcases for the ICF and fold-const that would lead
to wrong code if alias sets was ignored early.
Honza
* fold-const.c (operand_equal_p): Before inlining do not permit
transformations that would break with strict aliasing.
* ipa-inline.c (can_inline_edge_p) Use merged_comdat.
* ipa-inline-transform.c (inline_call): When inlining merged comdat do
not drop strict_aliasing flag of caller.
* cgraphclones.c (cgraph_node::create_clone): Use merged_comdat.
* cgraph.c (cgraph_node::dump): Dump merged_comdat.
* ipa-icf.c (sem_function::merge): Drop merged_comdat when merging
comdat and non-comdat.
* cgraph.h (cgraph_node): Rename merged to merged_comdat.
* ipa-inline-analysis.c (simple_edge_hints): Check both merged_comdat
and icf_merged.
* lto-symtab.c (lto_cgraph_replace_node): Update code computing
merged_comdat.
Index: fold-const.c
===================================================================
--- fold-const.c (revision 231239)
+++ fold-const.c (working copy)
@@ -2987,7 +2987,7 @@ operand_equal_p (const_tree arg0, const_
flags)))
return 0;
/* Verify that accesses are TBAA compatible. */
- if (flag_strict_aliasing
+ if ((flag_strict_aliasing || !cfun->after_inlining)
&& (!alias_ptr_types_compatible_p
(TREE_TYPE (TREE_OPERAND (arg0, 1)),
TREE_TYPE (TREE_OPERAND (arg1, 1)))
Index: ipa-inline.c
===================================================================
--- ipa-inline.c (revision 231239)
+++ ipa-inline.c (working copy)
@@ -466,7 +466,7 @@ can_inline_edge_p (struct cgraph_edge *e
optimized with the optimization flags of module they are used in.
Also do not care about mixing up size/speed optimization when
DECL_DISREGARD_INLINE_LIMITS is set. */
- else if ((callee->merged
+ else if ((callee->merged_comdat
&& !lookup_attribute ("optimize",
DECL_ATTRIBUTES (caller->decl)))
|| DECL_DISREGARD_INLINE_LIMITS (callee->decl))
Index: ipa-inline-transform.c
===================================================================
--- ipa-inline-transform.c (revision 231239)
+++ ipa-inline-transform.c (working copy)
@@ -322,11 +322,26 @@ inline_call (struct cgraph_edge *e, bool
if (DECL_FUNCTION_PERSONALITY (callee->decl))
DECL_FUNCTION_PERSONALITY (to->decl)
= DECL_FUNCTION_PERSONALITY (callee->decl);
+
+ /* merged_comdat indicate that function was originally COMDAT and merged
+ from multiple units. Because every unit using COMDAT must also define it,
+ we know that the function is safe to build with each of the optimization
+ flags used used to compile them.
+
+ If one unit is compiled with -fstrict-aliasing and
+ other with -fno-strict-aliasing we may bypass dropping the
+ flag_strict_aliasing because we know it would be valid to inline
+ -fstrict-aliaisng variant of the calee, too. Unless optimization
+ attribute was used, the caller and COMDAT callee must have been
+ compiled with the same flags. */
if (!opt_for_fn (callee->decl, flag_strict_aliasing)
- && opt_for_fn (to->decl, flag_strict_aliasing))
+ && opt_for_fn (to->decl, flag_strict_aliasing)
+ && (!callee->merged_comdat
+ || lookup_attribute ("optimization",
+ DECL_ATTRIBUTES (e->caller->decl))
+ || lookup_attribute ("optimization", DECL_ATTRIBUTES (callee->decl))))
{
struct gcc_options opts = global_options;
-
cl_optimization_restore (&opts,
TREE_OPTIMIZATION (DECL_FUNCTION_SPECIFIC_OPTIMIZATION (to->decl)));
opts.x_flag_strict_aliasing = false;
Index: cgraphclones.c
===================================================================
--- cgraphclones.c (revision 231239)
+++ cgraphclones.c (working copy)
@@ -433,7 +433,7 @@ cgraph_node::create_clone (tree new_decl
new_node->tp_first_run = tp_first_run;
new_node->tm_clone = tm_clone;
new_node->icf_merged = icf_merged;
- new_node->merged = merged;
+ new_node->merged_comdat = merged_comdat;
new_node->clone.tree_map = NULL;
new_node->clone.args_to_skip = args_to_skip;
Index: lto/lto-symtab.c
===================================================================
--- lto/lto-symtab.c (revision 231239)
+++ lto/lto-symtab.c (working copy)
@@ -63,8 +63,9 @@ lto_cgraph_replace_node (struct cgraph_n
gcc_assert (!prevailing_node->global.inlined_to);
prevailing_node->mark_address_taken ();
}
- if (node->definition && prevailing_node->definition)
- prevailing_node->merged = true;
+ if (node->definition && prevailing_node->definition
+ && DECL_COMDAT (node->decl) && DECL_COMDAT (prevailing_node->decl))
+ prevailing_node->merged_comdat = true;
/* Redirect all incoming edges. */
compatible_p
Index: cgraph.c
===================================================================
--- cgraph.c (revision 231239)
+++ cgraph.c (working copy)
@@ -1994,6 +1994,8 @@ cgraph_node::dump (FILE *f)
fprintf (f, " tm_clone");
if (icf_merged)
fprintf (f, " icf_merged");
+ if (merged_comdat)
+ fprintf (f, " merged_comdat");
if (nonfreeing_fn)
fprintf (f, " nonfreeing_fn");
if (DECL_STATIC_CONSTRUCTOR (decl))
Index: ipa-icf.c
===================================================================
--- ipa-icf.c (revision 231239)
+++ ipa-icf.c (working copy)
@@ -1352,10 +1352,15 @@ sem_function::merge (sem_item *alias_ite
gcc_assert (alias->icf_merged || remove || redirect_callers);
original->icf_merged = true;
- /* Inform the inliner about cross-module merging. */
- if ((original->lto_file_data || alias->lto_file_data)
- && original->lto_file_data != alias->lto_file_data)
- local_original->merged = original->merged = true;
+ /* We use merged flag to track cases where COMDAT function is known to be
+ compatible its callers. If we merged in non-COMDAT, we need to give up
+ on this optimization. */
+ if (original->merged_comdat && !alias->merged_comdat)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Dropping merged_comdat flag.\n\n");
+ local_original->merged_comdat = original->merged_comdat = false;
+ }
if (remove)
{
Index: cgraph.h
===================================================================
--- cgraph.h (revision 231239)
+++ cgraph.h (working copy)
@@ -1333,7 +1333,7 @@ public:
accesses trapping. */
unsigned nonfreeing_fn : 1;
/* True if there was multiple COMDAT bodies merged by lto-symtab. */
- unsigned merged : 1;
+ unsigned merged_comdat : 1;
/* True if function was created to be executed in parallel. */
unsigned parallelized_function : 1;
/* True if function is part split out by ipa-split. */
Index: ipa-inline-analysis.c
===================================================================
--- ipa-inline-analysis.c (revision 231239)
+++ ipa-inline-analysis.c (working copy)
@@ -3708,7 +3708,7 @@ simple_edge_hints (struct cgraph_edge *e
if (callee->lto_file_data && edge->caller->lto_file_data
&& edge->caller->lto_file_data != callee->lto_file_data
- && !callee->merged)
+ && !callee->merged_comdat && !callee->icf_merged)
hints |= INLINE_HINT_cross_module;
return hints;
