[gcc r14-7028] Fix segfault during delay slot scheduling pass

[Eric Botcazou]

https://gcc.gnu.org/g:f34141730266600b615b91d563a85a0b60223b3e

commit r14-7028-gf34141730266600b615b91d563a85a0b60223b3e
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Tue Jan 9 10:14:29 2024 +0100

    Fix segfault during delay slot scheduling pass
    
    This is a small regression present on the mainline and 13 branch, although
    the underlying problem has probably been there for ages, in the form of a
    segfault during the delay slot scheduling pass, for a function that falls
    through to exit without any instruction generated for the end of function.
    
    gcc/
            PR rtl-optimization/113140
            * reorg.cc (fill_slots_from_thread): If we are to branch after the
            last instruction of the function, create an end label.
    
    gcc/testsuite/
            * g++.dg/opt/delay-slot-2.C: New test.

Diff:
---
 gcc/reorg.cc                            | 13 ++++++++-----
 gcc/testsuite/g++.dg/opt/delay-slot-2.C | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/gcc/reorg.cc b/gcc/reorg.cc
index e85af7134f4..99228a22c69 100644
--- a/gcc/reorg.cc
+++ b/gcc/reorg.cc
@@ -2641,7 +2641,8 @@ fill_slots_from_thread (rtx_jump_insn *insn, rtx condition,
      arithmetic insn after the jump insn and put the arithmetic insn in the
      delay slot.  If we can't do this, return.  */
   if (delay_list->is_empty () && likely
-      && new_thread && !ANY_RETURN_P (new_thread)
+      && new_thread
+      && !ANY_RETURN_P (new_thread)
       && NONJUMP_INSN_P (new_thread)
       && !RTX_FRAME_RELATED_P (new_thread)
       && GET_CODE (PATTERN (new_thread)) != ASM_INPUT
@@ -2729,14 +2730,16 @@ fill_slots_from_thread (rtx_jump_insn *insn, rtx condition,
 
       gcc_assert (thread_if_true);
 
-      if (new_thread && simplejump_or_return_p (new_thread)
+      if (new_thread
+	  && simplejump_or_return_p (new_thread)
 	  && redirect_with_delay_list_safe_p (insn,
 					      JUMP_LABEL (new_thread),
 					      *delay_list))
-	new_thread = follow_jumps (JUMP_LABEL (new_thread), insn,
-				   &crossing);
+	new_thread = follow_jumps (JUMP_LABEL (new_thread), insn, &crossing);
 
-      if (ANY_RETURN_P (new_thread))
+      if (!new_thread)
+	label = find_end_label (simple_return_rtx);
+      else if (ANY_RETURN_P (new_thread))
 	label = find_end_label (new_thread);
       else if (LABEL_P (new_thread))
 	label = new_thread;
diff --git a/gcc/testsuite/g++.dg/opt/delay-slot-2.C b/gcc/testsuite/g++.dg/opt/delay-slot-2.C
new file mode 100644
index 00000000000..3810503b1a4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/delay-slot-2.C
@@ -0,0 +1,32 @@
+// PR rtl-optimization/113140
+// Reduced testcase by Rainer Orth <ro@gcc.gnu.org>
+
+// { dg-options "-O -w" }
+
+int *m();
+struct StaticValue {
+  long _val;
+  void setM(int *) { _val = 0; }
+};
+struct Value : StaticValue {
+  template <typename T> T *as();
+};
+Value *alloc();
+struct Scoped {
+  Scoped() {
+    Value v;
+    ptr = alloc();
+    Value *__trans_tmp_1 = v.as<Value>();
+    ptr->setM(__trans_tmp_1 ? m() : 0);
+  }
+  Value *ptr;
+};
+struct QObjectMethod {
+  unsigned long long callInternal() const;
+};
+unsigned long long QObjectMethod::callInternal() const {
+  [] {
+    if (Scoped(); 0)
+      ;
+  }();
+}