I didn't implement this before today as I had not see any code
where this would make a difference. I noticed while looking into
regressions an uninitialized warning that shows up only with
-fsanitize=address. This because SRA causes some extra total
scalaization when using -fsanitize=address. Which in turn exposes
an uninitialized warning. This fixes the uninitialized warning
by doing a simple copy prop into the return statement.
That is if we have:
```
D.3407 = D.3418;
return D.3407;
```
turn it into:
```
D.3407 = D.3418;
return D.3418;
```
This forces SRA not to do total scalarization on D.3418 and allows for better
code
too.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/95825
gcc/ChangeLog:
* tree-ssa-forwprop.cc (optimize_agr_copyprop_return): New function.
(optimize_agr_copyprop): Call optimize_agr_copyprop_return
for return statements.
gcc/testsuite/ChangeLog:
* g++.dg/warn/uninit-pr95825-1.C: New test.
* gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
---
gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C | 22 +++++++++++
.../tree-ssa/copy-prop-aggregate-return-1.c | 22 +++++++++++
gcc/tree-ssa-forwprop.cc | 37 +++++++++++++++++++
3 files changed, 81 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
diff --git a/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
b/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
new file mode 100644
index 00000000000..01a9b26a1f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
@@ -0,0 +1,22 @@
+// { dg-do compile }
+// { dg-options "-O1 -fsanitize=address" }
+
+// PR tree-optimization/95825
+
+struct s1
+{
+ char init;
+ int value;
+};
+
+static struct s1 f()
+{
+ struct s1 t;
+ t.init = 0;
+ return t; /* { dg-bogus "is used uninitialized" } */
+}
+
+struct s1 g()
+{
+ return f();
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
new file mode 100644
index 00000000000..f402931a0ee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-forwprop1-details" } */
+
+struct s1
+{
+ char init;
+ int value;
+};
+
+static inline struct s1 f()
+{
+ struct s1 t;
+ t.init = 0;
+ return t;
+}
+
+struct s1 g()
+{
+ return f();
+}
+
+/* { dg-final { scan-tree-dump-times "after previous" 1 "forwprop1"} } */
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index b1d63e189bd..c4fde7b4aae 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -1721,6 +1721,41 @@ optimize_agr_copyprop_arg (gimple *defstmt, gcall *call,
update_stmt (call);
}
+/* Helper function for optimize_agr_copyprop, propagate aggregates
+ into the return stmt USE if the operand of the return matches DEST;
+ replacing it with SRC. */
+static void
+optimize_agr_copyprop_return (gimple *defstmt, greturn *use,
+ tree dest, tree src)
+{
+ tree rvalue = gimple_return_retval (use);
+ if (!rvalue
+ || TREE_CODE (rvalue) == SSA_NAME
+ || is_gimple_min_invariant (rvalue)
+ || TYPE_VOLATILE (TREE_TYPE (rvalue)))
+ return;
+ tree newsrc = new_src_based_on_copy (rvalue, dest, src);
+ if (!newsrc)
+ return;
+ /* Currently only support decls, could support VCEs too? */
+ if (!DECL_P (newsrc))
+ return;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Simplified\n ");
+ print_gimple_stmt (dump_file, use, 0, dump_flags);
+ fprintf (dump_file, "after previous\n ");
+ print_gimple_stmt (dump_file, defstmt, 0, dump_flags);
+ }
+ gimple_return_set_retval (use, newsrc);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "into\n ");
+ print_gimple_stmt (dump_file, use, 0, dump_flags);
+ }
+ update_stmt (use);
+}
+
/* Optimizes
DEST = SRC;
DEST2 = DEST; # DEST2 = SRC2;
@@ -1764,6 +1799,8 @@ optimize_agr_copyprop (gimple *stmt)
optimize_agr_copyprop_1 (stmt, use_stmt, dest, src);
else if (is_gimple_call (use_stmt))
optimize_agr_copyprop_arg (stmt, as_a<gcall*>(use_stmt), dest, src);
+ else if (is_a<greturn*> (use_stmt))
+ optimize_agr_copyprop_return (stmt, as_a<greturn*>(use_stmt), dest,
src);
}
}
--
2.43.0
