[gcc r15-7269] tree-ssa-dce: Avoid creating invalid BBs with no outgoing edge (PR117892)

[Martin Jambor via Gcc-cvs]

https://gcc.gnu.org/g:3d07e7bf13d4aec794dd25b5090c139b4d78283d

commit r15-7269-g3d07e7bf13d4aec794dd25b5090c139b4d78283d
Author: Martin Jambor <mjam...@suse.cz>
Date:   Wed Jan 29 10:51:08 2025 +0100

    tree-ssa-dce: Avoid creating invalid BBs with no outgoing edge (PR117892)
    
    Zhendong Su and Michal Jireš found out that our gimple DSE pass can,
    under fairly specific conditions, remove a noreturn call which then
    leaves behind a "normal" BB with no successor edges which following
    passes do not expect.  This patch simply tells the pass to leave such
    calls alone even when they otherwise appear to be dead.
    
    Interestingly, our CFG verifier does not report this.  I'll put on my
    todo list to add a test for it in the next stage 1.
    
    gcc/ChangeLog:
    
    2025-01-28  Martin Jambor  <mjam...@suse.cz>
    
            PR tree-optimization/117892
            * tree-ssa-dse.cc (dse_optimize_call): Leave control-altering
            noreturn calls alone.
    
    gcc/testsuite/ChangeLog:
    
    2025-01-27  Martin Jambor  <mjam...@suse.cz>
    
            PR tree-optimization/117892
            * gcc.dg/tree-ssa/pr117892.c: New test.
            * gcc.dg/tree-ssa/pr118517.c: Likewise.
    
    co-authored-by: Michal Jireš <mji...@suse.cz>

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr117892.c | 17 +++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr118517.c | 11 +++++++++++
 gcc/tree-ssa-dse.cc                      |  6 ++++--
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr117892.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr117892.c
new file mode 100644
index 000000000000..d9b9c15095fc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr117892.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+
+
+volatile int a;
+void b(int *c) {
+  int *d = 0;
+  *c = 0;
+  *d = 0;
+  __builtin_abort();
+}
+int main() {
+  int f;
+  if (a)
+    b(&f);
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr118517.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr118517.c
new file mode 100644
index 000000000000..3a34f6788a9c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr118517.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-ipa-pure-const" } */
+
+void __attribute__((noreturn)) bar(void) {
+  __builtin_unreachable ();
+}
+
+int p;
+void foo() {
+  if (p) bar();
+}
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 753d7ef148ba..bc632e384841 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -1396,8 +1396,10 @@ dse_optimize_call (gimple_stmt_iterator *gsi, sbitmap 
live_bytes)
   if (!node)
     return false;
 
-  if (stmt_could_throw_p (cfun, stmt)
-      && !cfun->can_delete_dead_exceptions)
+  if ((stmt_could_throw_p (cfun, stmt)
+       && !cfun->can_delete_dead_exceptions)
+      || ((gimple_call_flags (stmt) & ECF_NORETURN)
+         && gimple_call_ctrl_altering_p (stmt)))
     return false;
 
   /* If return value is used the call is not dead.  */