Hi!
Here is my attempt at the PR119614 LTO fix.
Of course, if Martin can come up with something cleaner, let's go with that
instead.
This patch just remembers when ipa_record_return_value_range was set
to a singleton range with CONSTANT_CLASS_P value and propagates that value
through LTO to ltrans where ipa_return_value_range used by tailc pass can
consume it.
Initially I wanted to store it in cgraph_node as a tree, but haven't figured
out how to stream that tree out/in, so this patch stores it as an attribute
instead, which is streamed automatically.
Bootstrapped/regtested on x86_64-linux and i686-linux.
2025-04-14 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/119614
* ipa-prop.cc: Include attribs.h.
(ipa_record_return_value_range): Set "singleton retval" attribute if
the recorded range is singleton with CONSTANT_CLASS_P value, or
remove it otherwise.
(ipa_return_value_range): Use "singleton retval" attribute and create
singleton range from it as fallback.
* g++.dg/lto/pr119614_0.C: New test.
--- gcc/ipa-prop.cc.jj 2025-04-10 17:14:31.689344793 +0200
+++ gcc/ipa-prop.cc 2025-04-14 08:02:15.083339571 +0200
@@ -60,6 +60,7 @@ along with GCC; see the file COPYING3.
#include "gimple-range.h"
#include "value-range-storage.h"
#include "vr-values.h"
+#include "attribs.h"
/* Function summary where the parameter infos are actually stored. */
ipa_node_params_t *ipa_node_params_sum = NULL;
@@ -6158,6 +6159,21 @@ ipa_record_return_value_range (value_ran
ipa_return_value_sum->disable_insertion_hook ();
}
ipa_return_value_sum->get_create (n)->vr = ipa_get_value_range (val);
+ tree valr;
+ if (flag_lto || flag_wpa)
+ {
+ if (val.singleton_p (&valr)
+ && CONSTANT_CLASS_P (valr)
+ && !tree_expr_nan_p (valr))
+ DECL_ATTRIBUTES (current_function_decl)
+ = tree_cons (get_identifier ("singleton retval"), valr,
+ DECL_ATTRIBUTES (current_function_decl));
+ else
+ DECL_ATTRIBUTES (current_function_decl)
+ = remove_attribute ("singleton retval",
+ DECL_ATTRIBUTES (current_function_decl));
+ }
+
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Recording return range ");
@@ -6172,7 +6188,7 @@ bool
ipa_return_value_range (value_range &range, tree decl)
{
cgraph_node *n = cgraph_node::get (decl);
- if (!n || !ipa_return_value_sum)
+ if (!n || (!ipa_return_value_sum && !flag_ltrans))
return false;
enum availability avail;
n = n->ultimate_alias_target (&avail);
@@ -6180,11 +6196,21 @@ ipa_return_value_range (value_range &ran
return false;
if (n->decl != decl && !useless_type_conversion_p (TREE_TYPE (decl),
TREE_TYPE (n->decl)))
return false;
- ipa_return_value_summary *v = ipa_return_value_sum->get (n);
- if (!v)
- return false;
- v->vr->get_vrange (range);
- return true;
+ if (ipa_return_value_sum)
+ if (ipa_return_value_summary *v = ipa_return_value_sum->get (n))
+ {
+ v->vr->get_vrange (range);
+ return true;
+ }
+ if (tree attr = lookup_attribute ("singleton retval", DECL_ATTRIBUTES
(n->decl)))
+ {
+ value_range vr (TREE_VALUE (attr), TREE_VALUE (attr));
+ if (is_a <frange> (vr))
+ (as_a <frange> (vr)).clear_nan ();
+ range = vr;
+ return true;
+ }
+ return false;
}
/* Reset all state within ipa-prop.cc so that we can rerun the compiler
--- gcc/testsuite/g++.dg/lto/pr119614_0.C.jj 2025-04-14 08:06:08.774121960
+0200
+++ gcc/testsuite/g++.dg/lto/pr119614_0.C 2025-04-07 08:42:35.629686614
+0200
@@ -0,0 +1,34 @@
+// PR tree-optimization/119614
+// { dg-lto-do link }
+// { dg-lto-options { { -O2 -fPIC -flto -flto-partition=max } } }
+// { dg-require-effective-target shared }
+// { dg-require-effective-target fpic }
+// { dg-require-effective-target musttail }
+// { dg-extra-ld-options "-shared" }
+
+struct S {} b;
+char *foo ();
+int e, g;
+void bar ();
+void corge (S);
+
+[[gnu::noinline]] static char *
+baz ()
+{
+ bar ();
+ return 0;
+}
+
+const char *
+qux ()
+{
+ if (e)
+ {
+ S a = b;
+ corge (a);
+ if (g)
+ return 0;
+ [[gnu::musttail]] return baz ();
+ }
+ return foo ();
+}
Jakub
