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

[Jakub Jelinek via Gcc-patches]

Hi!

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

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2021-12-28  Jakub Jelinek  <ja...@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.

--- gcc/optabs.c.jj     2021-09-06 14:47:43.212049793 +0200
+++ gcc/optabs.c        2021-12-27 11:03:11.575586585 +0100
@@ -1135,6 +1135,10 @@ expand_doubleword_mod (machine_mode mode
 
       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;
@@ -1228,6 +1232,10 @@ expand_doubleword_divmod (machine_mode m
     }
 
   /* 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;
--- gcc/testsuite/gcc.dg/pr103838.c.jj  2021-12-27 11:07:08.920225699 +0100
+++ gcc/testsuite/gcc.dg/pr103838.c     2021-12-27 11:06:57.555386630 +0100
@@ -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;
+    }
+}

        Jakub