[gcc r11-9491] optabs: Fix up checking for CALLs in newly added code by double-word divmod [PR103838]

[gcc r11-9491] optabs: Fix up checking for CALLs in newly added code by double-word divmod [PR103838]

[Jakub Jelinek]

https://gcc.gnu.org/g:2712f1249e0a8dd663a02bdf710a455fe5b14e3f

commit r11-9491-g2712f1249e0a8dd663a02bdf710a455fe5b14e3f
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Dec 28 17:39:23 2021 +0100

    optabs: Fix up checking for CALLs in newly added code by double-word divmod [PR103838]
    
    These two spots are meant to punt if the newly added code contains
    any CALL_INSNs, because in that case having a large sequence of insns
    that also calls something is undesirable, better have one call that
    is optimized in itself well.
    The functions do last = get_last_insn (); before emitting any insns
    (and expand_binop as the ultimate caller uses delete_insns_since if
    the expansion fails), but the checks were incorrect for 2 reasons:
    1) it checked not just what follows after that last insn, but also
       the last insn itself; so, if the division or modulo is immediately
       preceded by a CALL_INSN, then we punt; this also causes -fcompare-debug
       failures if the CALL_INSN is with -g followed by one or more DEBUG_INSNs
    2) if get_last_insn () is NULL (i.e. emitting into a new sequence), then
       we didn't check anything
    
    2021-12-28  Jakub Jelinek  <jakub@redhat.com>
    
            PR debug/103838
            * optabs.c (expand_doubleword_mod, expand_doubleword_divmod): Only
            check newly added insns for CALL_P, not the last insn of previous
            code.
    
            * gcc.dg/pr103838.c: New test.
    
    (cherry picked from commit 78ee8381bf0ebd09a92936bdb9e1b5c9fc85ad88)

Diff:
---
 gcc/optabs.c                    |  8 ++++++++
 gcc/testsuite/gcc.dg/pr103838.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/gcc/optabs.c b/gcc/optabs.c
index f4614a39458..e55c1785b4e 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -1113,6 +1113,10 @@ expand_doubleword_mod (machine_mode mode, rtx op0, rtx op1, bool unsignedp)
 
       remainder = convert_modes (mode, word_mode, remainder, unsignedp);
       /* Punt if we need any library calls.  */
+      if (last)
+	last = NEXT_INSN (last);
+      else
+	last = get_insns ();
       for (; last; last = NEXT_INSN (last))
 	if (CALL_P (last))
 	  return NULL_RTX;
@@ -1206,6 +1210,10 @@ expand_doubleword_divmod (machine_mode mode, rtx op0, rtx op1, rtx *rem,
     }
 
   /* Punt if we need any library calls.  */
+  if (last)
+    last = NEXT_INSN (last);
+  else
+    last = get_insns ();
   for (; last; last = NEXT_INSN (last))
     if (CALL_P (last))
       return NULL_RTX;
diff --git a/gcc/testsuite/gcc.dg/pr103838.c b/gcc/testsuite/gcc.dg/pr103838.c
new file mode 100644
index 00000000000..cde44e6e4e3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr103838.c
@@ -0,0 +1,28 @@
+/* PR debug/103838 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fcompare-debug" } */
+
+#ifdef __SIZEOF_INT128__
+__int128 m;
+#else
+long long m;
+#endif
+int n;
+
+__attribute__((noinline)) void
+bar (void)
+{
+  n += !!m;
+}
+
+void
+foo (void)
+{
+  int i;
+
+  for (i = 0; i < 2; ++i)
+    {
+      bar ();
+      m /= 3;
+    }
+}