[PATCH] tree-optimization/100398 - avoid DSE of control flow stmt

[Richard Biener]

The following makes sure to preserve control altering stmts
when removing trivially dead stmts in DSE.

Boostrapped and tested on x86_64-unknown-linux-gnu, pushed.

2021-05-04  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/100398
        * tree-ssa-dse.c (pass_dse::execute): Preserve control
        altering stmts.

        * gcc.dg/torture/pr100398.c: New testcase.
---
 gcc/testsuite/gcc.dg/torture/pr100398.c | 13 +++++++++++++
 gcc/tree-ssa-dse.c                      |  1 +
 2 files changed, 14 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr100398.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr100398.c 
b/gcc/testsuite/gcc.dg/torture/pr100398.c
new file mode 100644
index 00000000000..41eaddee27e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr100398.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+
+int
+test5_limit (void)
+{
+  int addr;
+
+  asm goto ("" : "+r" (addr) : : : t_err);
+  return 0;
+
+ t_err:
+  return 1;
+}
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index dfa6d314727..d7cf7477028 100644
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -1219,6 +1219,7 @@ pass_dse::execute (function *fun)
                 dead SSA defs.  */
              if (has_zero_uses (DEF_FROM_PTR (def_p))
                  && !gimple_has_side_effects (stmt)
+                 && !is_ctrl_altering_stmt (stmt)
                  && !stmt_unremovable_because_of_non_call_eh_p (cfun, stmt))
                {
                  if (dump_file && (dump_flags & TDF_DETAILS))
-- 
2.26.2