regrename: Don't rename the dest of a REG_CFA_REGISTER (PR85645)

We should never change the destination of a REG_CFA_REGISTER, just
like for insns with a REG_CFA_RESTORE, because we need to have the
same control flow information on all branches that join.  It is very
doubtful that renaming the scratch registers used for prologue/epilogue
will help anything either.


	PR rtl-optimization/85645
	* regrename.c (build_def_use): Also kill the chains that include the
	destination of a REG_CFA_REGISTER note.

From-SVN: r260075

gcc/ChangeLog

 2018-05-09  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	PR rtl-optimization/85645
+	* regrename.c (build_def_use): Also kill the chains that include the
+	destination of a REG_CFA_REGISTER note.
+
+2018-05-09  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/85645
 	*  regcprop.c (copyprop_hardreg_forward_1): Don't propagate into an
 	insn that has a REG_CFA_REGISTER note.
 

gcc/regrename.c

@@ -1661,7 +1661,8 @@ 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.
+	     (8) For any REG_CFA_RESTORE or REG_CFA_REGISTER, kill any chain
+	         containing its dest.
 
 	     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
@@ -1882,10 +1883,20 @@ build_def_use (basic_block bb)
 	      }
 
 	  /* Step 8: Kill the chains involving register restores.  Those
-	     should restore _that_ register.  */
+	     should restore _that_ register.  Similar for REG_CFA_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);
+	    if (REG_NOTE_KIND (note) == REG_CFA_RESTORE
+		|| REG_NOTE_KIND (note) == REG_CFA_REGISTER)
+	      {
+		rtx *x = &XEXP (note, 0);
+		if (!*x)
+		  x = &PATTERN (insn);
+		if (GET_CODE (*x) == PARALLEL)
+		  x = &XVECEXP (*x, 0, 0);
+		if (GET_CODE (*x) == SET)
+		  x = &SET_DEST (*x);
+		scan_rtx (insn, x, NO_REGS, mark_all_read, OP_IN);
+	      }
 	}
       else if (DEBUG_BIND_INSN_P (insn)
 	       && !VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))