[gcc r10-9473] tree-cfg: Fix up gimple_merge_blocks FORCED_LABEL handling [PR99034]

[Jakub Jelinek]

https://gcc.gnu.org/g:33be24d77d3d8f0c992eb344ce63f78e14cf753d

commit r10-9473-g33be24d77d3d8f0c992eb344ce63f78e14cf753d
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Feb 19 12:14:39 2021 +0100

    tree-cfg: Fix up gimple_merge_blocks FORCED_LABEL handling [PR99034]
    
    The verifiers require that DECL_NONLOCAL or EH_LANDING_PAD_NR
    labels are always the first label if there is more than one label.
    
    When merging blocks, we don't honor that though.
    On the following testcase, we try to merge blocks:
    <bb 13> [count: 0]:
    <L2>:
    S::~S (&s);
    
    and
    <bb 15> [count: 0]:
    <L0>:
    resx 1
    
    where <L2> is landing pad and <L0> is FORCED_LABEL.  And the code puts
    the FORCED_LABEL before the landing pad label, violating the verification
    requirements.
    
    The following patch fixes it by moving the FORCED_LABEL after the
    DECL_NONLOCAL or EH_LANDING_PAD_NR label if it is the first label.
    
    2021-02-19  Jakub Jelinek  <jakub@redhat.com>
    
            PR ipa/99034
            * tree-cfg.c (gimple_merge_blocks): If bb a starts with eh landing
            pad or non-local label, put FORCED_LABELs from bb b after that label
            rather than before it.
    
            * g++.dg/opt/pr99034.C: New test.
    
    (cherry picked from commit 37bde2f87267908a93c07856317a28827f8284f7)

Diff:
---
 gcc/testsuite/g++.dg/opt/pr99034.C | 23 +++++++++++++++++++++++
 gcc/tree-cfg.c                     | 12 +++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/opt/pr99034.C b/gcc/testsuite/g++.dg/opt/pr99034.C
new file mode 100644
index 00000000000..d791a14b136
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr99034.C
@@ -0,0 +1,23 @@
+// PR ipa/99034
+// { dg-do compile }
+// { dg-options "-O2" }
+
+void *b[5];
+void foo (void);
+struct S { ~S (); };
+
+static inline void
+__attribute__((always_inline))
+bar (int d)
+{
+  S s;
+  while (d)
+    foo ();
+}
+
+void
+baz (void)
+{
+  bar (2);
+  __builtin_setjmp (b);
+}
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index f2f2e480330..1af59fc6fe9 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -2133,7 +2133,17 @@ gimple_merge_blocks (basic_block a, basic_block b)
 	  if (FORCED_LABEL (label))
 	    {
 	      gimple_stmt_iterator dest_gsi = gsi_start_bb (a);
-	      gsi_insert_before (&dest_gsi, stmt, GSI_NEW_STMT);
+	      tree first_label = NULL_TREE;
+	      if (!gsi_end_p (dest_gsi))
+		if (glabel *first_label_stmt
+		    = dyn_cast <glabel *> (gsi_stmt (dest_gsi)))
+		  first_label = gimple_label_label (first_label_stmt);
+	      if (first_label
+		  && (DECL_NONLOCAL (first_label)
+		      || EH_LANDING_PAD_NR (first_label) != 0))
+		gsi_insert_after (&dest_gsi, stmt, GSI_NEW_STMT);
+	      else
+		gsi_insert_before (&dest_gsi, stmt, GSI_NEW_STMT);
 	    }
 	  /* Other user labels keep around in a form of a debug stmt.  */
 	  else if (!DECL_ARTIFICIAL (label) && MAY_HAVE_DEBUG_BIND_STMTS)