[gcc r14-11373] gimple: sccopy: Prune removed statements from SCCs [PR117919]

[Filip Kastl via Gcc-cvs]

https://gcc.gnu.org/g:6ffbc711afbda9446df51fd2b542ecd61853283d

commit r14-11373-g6ffbc711afbda9446df51fd2b542ecd61853283d
Author: Filip Kastl <fka...@suse.cz>
Date:   Sun Mar 2 06:39:17 2025 +0100

    gimple: sccopy: Prune removed statements from SCCs [PR117919]
    
    While writing the sccopy pass I didn't realize that 'replace_uses_by ()' can
    remove portions of the CFG.  This happens when replacing arguments of some
    statement results in the removal of an EH edge.  Because of this sccopy can
    then work with GIMPLE statements that aren't part of the IR anymore.  In
    PR117919 this triggered an assertion within the pass which assumes that
    statements the pass works with are reachable.
    
    This patch tells the pass to notice when a statement isn't in the IR anymore
    and remove it from it's worklist.
    
            PR tree-optimization/117919
    
    gcc/ChangeLog:
    
            * gimple-ssa-sccopy.cc (scc_copy_prop::propagate): Prune
            statements that 'replace_uses_by ()' removed.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/pr117919.C: New test.
    
    Signed-off-by: Filip Kastl <fka...@suse.cz>
    (cherry picked from commit 5349aa2accdf34a7bf9cabd1447878aaadfc0e87)

Diff:
---
 gcc/gimple-ssa-sccopy.cc        | 13 +++++++++++
 gcc/testsuite/g++.dg/pr117919.C | 52 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/gcc/gimple-ssa-sccopy.cc b/gcc/gimple-ssa-sccopy.cc
index 138ee9a0ac48..d4d06f3b13e7 100644
--- a/gcc/gimple-ssa-sccopy.cc
+++ b/gcc/gimple-ssa-sccopy.cc
@@ -550,6 +550,19 @@ sccopy_propagate ()
     {
       vec<gimple *> scc = worklist.pop ();
 
+      /* When we do 'replace_scc_by_value' it may happen that some EH edges
+        get removed.  That means parts of CFG get removed.  Those may
+        contain copy statements.  For that reason we prune SCCs here.  */
+      unsigned i;
+      for (i = 0; i < scc.length (); i++)
+       if (gimple_bb (scc[i]) == NULL)
+         scc.unordered_remove (i);
+      if (scc.is_empty ())
+       {
+         scc.release ();
+         continue;
+       }
+
       auto_vec<gimple *> inner;
       hash_set<tree> outer_ops;
       tree last_outer_op = NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/pr117919.C b/gcc/testsuite/g++.dg/pr117919.C
new file mode 100644
index 000000000000..fa2d9c9cd1e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr117919.C
@@ -0,0 +1,52 @@
+/* PR tree-optimization/117919 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-forwprop -fnon-call-exceptions 
--param=early-inlining-insns=192 -std=c++20" } */
+
+char _M_p, _M_construct___beg;
+struct _Alloc_hider {
+  _Alloc_hider(char);
+};
+long _M_string_length;
+void _M_destroy();
+void _S_copy_chars(char *, char *, char *) noexcept;
+char _M_local_data();
+struct Trans_NS___cxx11_basic_string {
+  _Alloc_hider _M_dataplus;
+  bool _M_is_local() {
+    if (_M_local_data())
+      if (_M_string_length)
+        return true;
+    return false;
+  }
+  void _M_dispose() {
+    if (!_M_is_local())
+      _M_destroy();
+  }
+  char *_M_construct___end;
+  Trans_NS___cxx11_basic_string(Trans_NS___cxx11_basic_string &)
+      : _M_dataplus(0) {
+    struct _Guard {
+      ~_Guard() { _M_guarded->_M_dispose(); }
+      Trans_NS___cxx11_basic_string *_M_guarded;
+    } __guard0;
+    _S_copy_chars(&_M_p, &_M_construct___beg, _M_construct___end);
+  }
+};
+namespace filesystem {
+struct path {
+  path();
+  Trans_NS___cxx11_basic_string _M_pathname;
+};
+} // namespace filesystem
+struct FileWriter {
+  filesystem::path path;
+  FileWriter() : path(path) {}
+};
+struct LanguageFileWriter : FileWriter {
+  LanguageFileWriter(filesystem::path) {}
+};
+int
+main() {
+  filesystem::path output_file;
+  LanguageFileWriter writer(output_file);
+}