re PR middle-end/84040 (compilation time of gcc.c-torture/compile/limits-blockid.c is 50x slower)

	PR middle-end/84040
	* sched-deps.c (sched_macro_fuse_insns): Return immediately for
	debug insns.

From-SVN: r257119

gcc/ChangeLog

+2018-01-27  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/84040
+	* sched-deps.c (sched_macro_fuse_insns): Return immediately for
+	debug insns.
+
 2018-01-26  Jim Wilson  <jimw@sifive.com>
 
 	* config/riscv/riscv.h (MAX_FIXED_MODE_SIZE): New.

gcc/sched-deps.c

@@ -2834,10 +2834,16 @@ static void
 sched_macro_fuse_insns (rtx_insn *insn)
 {
   rtx_insn *prev;
+  /* No target hook would return true for debug insn as any of the
+     hook operand, and with very large sequences of only debug insns
+     where on each we call sched_macro_fuse_insns it has quadratic
+     compile time complexity.  */
+  if (DEBUG_INSN_P (insn))
+    return;
   prev = prev_nonnote_nondebug_insn (insn);
   if (!prev)
     return;
- 
+
   if (any_condjump_p (insn))
     {
       unsigned int condreg1, condreg2;