From: Jan Hubicka <hubicka@ucw.cz>
To: gcc-patches@gcc.gnu.org, rguenther@suse.de
Subject: PR middle-end/44813 (ICE in Mozilla build in ptr_deref_may_alias_decl_p)
Date: Sun, 04 Jul 2010 22:42:00 -0000 [thread overview]
Message-ID: <20100704224222.GB29130@kam.mff.cuni.cz> (raw)
Hi,
the testcase in PR (Richard is running minimizing on it) produce ICE because
ipa-split produce invalid gimple
*<retval> = funcall.part ();
where <retval> is not gimple register. It is function returning by reference
so we actually must write to retval directly for correctness. <retval> is not
gimple register because needs_to_live_in_memory returns true after calling
aggregate_value_p.
This is confused. For functions returning by reference retval is pointer and
as such it does not need to live in memory. aggregate_value_p is about return
value itself, that is *<retval> that lives in memory.
So this patch changes behaviour of needs_to_live_in_memory that has some consequences.
1) We get confused wanrings since tree-ssa-uninit.c considers retvals not initilized
at function entry. This is not valid for DECL_BY_REFERENCE>
2) tree-inline produces bogus &tmp_1=&tmp_1 for return statement, since it no longer
recognizes return value wrapped in SSA name.
3) Alias analysis don't know that <retval>.filed stores escape and thus must
be preserved
4) Statement verifier does type checking when return statement is not retval.
It should check DECL_BY_REFERENCE, but Richard plans to submit patch for it.
So I just patched around strengthening the check for SSA name of DECL_BY_REFERENCE>
Bootstrapped/regtested x86_64 and tested on Mozilla build. OK?
Honza
PR middle-end/44813
* tree-ssa-uninit.c (ssa_undefined_value_p): Retval_expr is initialized
for functions returning by reference.
* tree.c (needs_to_live_in_memory): Retval for functions returning by
reference does not need to live in memory.
* tree-inline.c (remap_gimple_stmt): Do not produce assignment
for functions returning by reference.
* tree-ssa-structalias.c (find_what_p_points_to): Look into result decls
same was as into parm decls.
* tree-cfg.c (verify_gimple_return): Expect RESULT_DECL to have SSA name.
Index: tree-ssa-uninit.c
===================================================================
--- tree-ssa-uninit.c (revision 161774)
+++ tree-ssa-uninit.c (working copy)
@@ -92,6 +92,12 @@ ssa_undefined_value_p (tree t)
if (TREE_CODE (var) == PARM_DECL)
return false;
+ /* When returning by reference the return address is actually a hidden
+ parameter. */
+ if (TREE_CODE (SSA_NAME_VAR (t)) == RESULT_DECL
+ && DECL_BY_REFERENCE (SSA_NAME_VAR (t)))
+ return false;
+
/* Hard register variables get their initial value from the ether. */
if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
return false;
Index: tree.c
===================================================================
--- tree.c (revision 161774)
+++ tree.c (working copy)
@@ -9750,6 +9750,7 @@ needs_to_live_in_memory (const_tree t)
return (TREE_ADDRESSABLE (t)
|| is_global_var (t)
|| (TREE_CODE (t) == RESULT_DECL
+ && !DECL_BY_REFERENCE (t)
&& aggregate_value_p (t, current_function_decl)));
}
Index: tree-inline.c
===================================================================
--- tree-inline.c (revision 161774)
+++ tree-inline.c (working copy)
@@ -1236,7 +1237,11 @@ remap_gimple_stmt (gimple stmt, copy_bod
If RETVAL is just the result decl, the result decl has
already been set (e.g. a recent "foo (&result_decl, ...)");
just toss the entire GIMPLE_RETURN. */
- if (retval && TREE_CODE (retval) != RESULT_DECL)
+ if (retval
+ && (TREE_CODE (retval) != RESULT_DECL
+ && (TREE_CODE (retval) != SSA_NAME
+ || !SSA_NAME_IS_DEFAULT_DEF (retval)
+ || TREE_CODE (SSA_NAME_VAR (retval)) != RESULT_DECL)))
{
copy = gimple_build_assign (id->retvar, retval);
/* id->retvar is already substituted. Skip it on later remapping. */
Index: tree-ssa-structalias.c
===================================================================
--- tree-ssa-structalias.c (revision 161774)
+++ tree-ssa-structalias.c (working copy)
@@ -5751,7 +5751,8 @@ find_what_p_points_to (tree p)
/* For parameters, get at the points-to set for the actual parm
decl. */
if (TREE_CODE (p) == SSA_NAME
- && TREE_CODE (SSA_NAME_VAR (p)) == PARM_DECL
+ && (TREE_CODE (SSA_NAME_VAR (p)) == PARM_DECL
+ || TREE_CODE (SSA_NAME_VAR (p)) == RESULT_DECL)
&& SSA_NAME_IS_DEFAULT_DEF (p))
lookup_p = SSA_NAME_VAR (p);
Index: tree-cfg.c
===================================================================
--- tree-cfg.c (revision 161774)
+++ tree-cfg.c (working copy)
@@ -3818,8 +3818,7 @@ verify_gimple_return (gimple stmt)
if (op == NULL)
return false;
- if (!is_gimple_val (op)
- && TREE_CODE (op) != RESULT_DECL)
+ if (!is_gimple_val (op) && TREE_CODE (op) != RESULT_DECL)
{
error ("invalid operand in return statement");
debug_generic_stmt (op);
@@ -3829,7 +3828,10 @@ verify_gimple_return (gimple stmt)
if (!useless_type_conversion_p (restype, TREE_TYPE (op))
/* ??? With C++ we can have the situation that the result
decl is a reference type while the return type is an aggregate. */
- && !(TREE_CODE (op) == RESULT_DECL
+ && !((TREE_CODE (op) == RESULT_DECL
+ || (TREE_CODE (op) == SSA_NAME
+ && SSA_NAME_IS_DEFAULT_DEF (op)
+ && TREE_CODE (SSA_NAME_VAR (op)) == RESULT_DECL))
&& TREE_CODE (TREE_TYPE (op)) == REFERENCE_TYPE
&& useless_type_conversion_p (restype, TREE_TYPE (TREE_TYPE (op)))))
{
next reply other threads:[~2010-07-04 22:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-04 22:42 Jan Hubicka [this message]
2010-07-05 9:43 ` Richard Guenther
2010-07-05 10:28 ` Jan Hubicka
2010-07-05 16:18 ` Jan Hubicka
2010-07-06 9:20 ` Richard Guenther
2011-01-16 20:09 ` H.J. Lu
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