regrename: Don't rename restores

A restore is supposed to restore some certain register.  Restoring it
into some other register will not work.  Don't.


	* regrename.c (build_def_use): Invalidate chains that have a
	REG_CFA_RESTORE on some instruction.

From-SVN: r241061

gcc/ChangeLog

 2016-10-12  Segher Boessenkool  <segher@kernel.crashing.org>
 
+	* regrename.c (build_def_use): Invalidate chains that have a
+	REG_CFA_RESTORE on some instruction.
+
+2016-10-12  Segher Boessenkool  <segher@kernel.crashing.org>
+
 	* dce.c (delete_unmarked_insns): Don't delete instructions with
 	a REG_CFA_RESTORE note.
 

gcc/regrename.c

@@ -1655,6 +1655,7 @@ build_def_use (basic_block bb)
 	     (6) For any non-earlyclobber write we find in an operand, make
 	         a new chain or mark the hard register as live.
 	     (7) For any REG_UNUSED, close any chains we just opened.
+	     (8) For any REG_CFA_RESTORE, kill any chain containing it.
 
 	     We cannot deal with situations where we track a reg in one mode
 	     and see a reference in another mode; these will cause the chain
@@ -1867,6 +1868,12 @@ build_def_use (basic_block bb)
 		scan_rtx (insn, &XEXP (note, 0), NO_REGS, terminate_dead,
 			  OP_IN);
 	      }
+
+	  /* Step 8: Kill the chains involving register restores.  Those
+	     should restore _that_ register.  */
+	  for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
+	    if (REG_NOTE_KIND (note) == REG_CFA_RESTORE)
+	      scan_rtx (insn, &XEXP (note, 0), NO_REGS, mark_all_read, OP_IN);
 	}
       else if (DEBUG_INSN_P (insn)
 	       && !VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))