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* [gcc r12-3064] Improve return slot handling in ipa-modref
@ 2021-08-23 7:22 Jan Hubicka
0 siblings, 0 replies; only message in thread
From: Jan Hubicka @ 2021-08-23 7:22 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:59f38935d189027f172b4813a6056addaceb7cd3
commit r12-3064-g59f38935d189027f172b4813a6056addaceb7cd3
Author: Jan Hubicka <hubicka@ucw.cz>
Date: Mon Aug 23 09:21:36 2021 +0200
Improve return slot handling in ipa-modref
gcc/ChangeLog:
* ipa-modref.c (analyze_ssa_name_flags): Improve handling of return slot.
gcc/testsuite/ChangeLog:
* g++.dg/tree-ssa/modref-1.C: New test.
Diff:
---
gcc/ipa-modref.c | 23 ++++++++++-------------
gcc/testsuite/g++.dg/tree-ssa/modref-1.C | 32 ++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+), 13 deletions(-)
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 549153865b8..cb0a314cbeb 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -1709,19 +1709,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
if (gimple_call_fn (use_stmt) == name)
lattice[index].merge (~EAF_NOCLOBBER);
- /* Return slot optimization would require bit of propagation;
- give up for now. */
- if (gimple_call_return_slot_opt_p (call)
- && gimple_call_lhs (call) != NULL_TREE
- && TREE_ADDRESSABLE (TREE_TYPE (gimple_call_lhs (call))))
- {
- if (dump_file)
- fprintf (dump_file, "%*s Unhandled return slot opt\n",
- depth * 4, "");
- lattice[index].merge (0);
- }
/* Recursion would require bit of propagation; give up for now. */
- else if (callee && !ipa && recursive_call_p (current_function_decl,
+ if (callee && !ipa && recursive_call_p (current_function_decl,
callee))
lattice[index].merge (0);
else
@@ -1735,7 +1724,15 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
/* Handle *name = func (...). */
if (gimple_call_lhs (call)
&& memory_access_to (gimple_call_lhs (call), name))
- lattice[index].merge_direct_store ();
+ {
+ lattice[index].merge_direct_store ();
+ /* Return slot optimization passes address of
+ LHS to callee via hidden parameter and this
+ may make LHS to escape. See PR 98499. */
+ if (gimple_call_return_slot_opt_p (call)
+ && TREE_ADDRESSABLE (TREE_TYPE (gimple_call_lhs (call))))
+ lattice[index].merge (EAF_NOREAD | EAF_DIRECT);
+ }
/* We do not track accesses to the static chain (we could)
so give up. */
diff --git a/gcc/testsuite/g++.dg/tree-ssa/modref-1.C b/gcc/testsuite/g++.dg/tree-ssa/modref-1.C
new file mode 100644
index 00000000000..c742dfe8b33
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/modref-1.C
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+struct S { int a; char b[20]; S(); S(S const&); };
+volatile int global;
+
+__attribute__ ((noinline,noclone))
+struct S noescape (int *b)
+{
+ struct S a;
+ a.a = b!=0;
+ global = 1;
+ return a;
+}
+
+void escape (struct S *p);
+
+__attribute__ ((noinline,noclone))
+int
+test(int *b)
+{
+ struct S s = noescape (b);
+ escape (&s);
+ return *b;
+}
+int test2()
+{
+ int b=1234;
+ test (&b);
+ return b;
+}
+// ipa-modref should analyze parameter B of test as noescape.
+// { dg-final { scan-tree-dump "return 1234" } }
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