combine: Don't make log_links for pc_rtx (PR84780 #c10)

distribute_links tries to place a log_link for whatever the destination
of the modified instruction is.  It shouldn't do that when that dest
is pc_rtx, which isn't actually a register.


	* combine.c (distribute_links): Don't make a link based on pc_rtx.

From-SVN: r258523

gcc/ChangeLog

+2018-03-14  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/84780
+	* combine.c (distribute_links): Don't make a link based on pc_rtx.
+
 2018-03-14  Martin Liska  <mliska@suse.cz>
 
 	* tree.c (record_node_allocation_statistics): Use

gcc/combine.c

@@ -14778,6 +14778,9 @@ distribute_links (struct insn_link *links)
 	     || GET_CODE (reg) == SUBREG)
 	reg = XEXP (reg, 0);
 
+      if (reg == pc_rtx)
+	continue;
+
       /* A LOG_LINK is defined as being placed on the first insn that uses
 	 a register and points to the insn that sets the register.  Start
 	 searching at the next insn after the target of the link and stop