From: Martin Jambor <mjambor@suse.cz>
Date: Wed, 29 Jan 2025 09:51:08 +0000 (+0100)
Subject: tree-ssa-dce: Avoid creating invalid BBs with no outgoing edge (PR117892)
X-Git-Tag: basepoints/gcc-16~2284
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3d07e7bf13d4aec794dd25b5090c139b4d78283d;p=thirdparty%2Fgcc.git

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  <mjambor@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  <mjambor@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 <mjires@suse.cz>
---

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 00000000000..d9b9c15095f
--- /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 00000000000..3a34f6788a9
--- /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 753d7ef148b..bc632e38484 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.  */