[RTL ifcvt] PR rtl-optimization/71594: ICE in noce_emit_cmove due to mismatched source modes

	PR rtl-optimization/71594
	* ifcvt.c (noce_convert_multiple_sets): Wrap new_val or old_val
	into subregs of appropriate mode before trying to emit a conditional
	move.

	* gcc.dg/torture/pr71594.c: New test.

From-SVN: r238013

1 files changed, 35 insertions, 0 deletions

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index fd29516..f7f120e 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -3228,6 +3228,41 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
       if (if_info->then_else_reversed)
 	std::swap (old_val, new_val);
 
+
+      /* We allow simple lowpart register subreg SET sources in
+	 bb_ok_for_noce_convert_multiple_sets.  Be careful when processing
+	 sequences like:
+	 (set (reg:SI r1) (reg:SI r2))
+	 (set (reg:HI r3) (subreg:HI (r1)))
+	 For the second insn new_val or old_val (r1 in this example) will be
+	 taken from the temporaries and have the wider mode which will not
+	 match with the mode of the other source of the conditional move, so
+	 we'll end up trying to emit r4:HI = cond ? (r1:SI) : (r3:HI).
+	 Wrap the two cmove operands into subregs if appropriate to prevent
+	 that.  */
+      if (GET_MODE (new_val) != GET_MODE (temp))
+	{
+	  machine_mode src_mode = GET_MODE (new_val);
+	  machine_mode dst_mode = GET_MODE (temp);
+	  if (GET_MODE_SIZE (src_mode) <= GET_MODE_SIZE (dst_mode))
+	    {
+	      end_sequence ();
+	      return FALSE;
+	    }
+	  new_val = lowpart_subreg (dst_mode, new_val, src_mode);
+	}
+      if (GET_MODE (old_val) != GET_MODE (temp))
+	{
+	  machine_mode src_mode = GET_MODE (old_val);
+	  machine_mode dst_mode = GET_MODE (temp);
+	  if (GET_MODE_SIZE (src_mode) <= GET_MODE_SIZE (dst_mode))
+	    {
+	      end_sequence ();
+	      return FALSE;
+	    }
+	  old_val = lowpart_subreg (dst_mode, old_val, src_mode);
+	}
+
       /* Actually emit the conditional move.  */
       rtx temp_dest = noce_emit_cmove (if_info, temp, cond_code,
 				       x, y, new_val, old_val);