PR target/42235
	* function.c (assign_parm_setup_reg): When an optab for extending
	exists, emit the insn directly and create a REG_EQUIV note.

Index: function.c
===================================================================
--- function.c	(revision 162146)
+++ function.c	(working copy)
@@ -2861,10 +2861,12 @@ static void
 assign_parm_setup_reg (struct assign_parm_data_all *all, tree parm,
 		       struct assign_parm_data_one *data)
 {
-  rtx parmreg;
+  rtx parmreg, validated_mem;
+  rtx equiv_stack_parm;
   enum machine_mode promoted_nominal_mode;
   int unsignedp = TYPE_UNSIGNED (TREE_TYPE (parm));
   bool did_conversion = false;
+  bool need_conversion, moved;
 
   /* Store the parm in a pseudoregister during the function, but we may
      need to do it in a wider mode.  Using 2 here makes the result
@@ -2891,10 +2893,46 @@ assign_parm_setup_reg (struct assign_par
 
   assign_parm_remove_parallels (data);
 
+  equiv_stack_parm = data->stack_parm;
+  validated_mem = validize_mem (data->entry_parm);
+
+  need_conversion = (data->nominal_mode != data->passed_mode
+		     || promoted_nominal_mode != data->promoted_mode);
+  moved = false;
+
   /* Copy the value into the register, thus bridging between
      assign_parm_find_data_types and expand_expr_real_1.  */
-  if (data->nominal_mode != data->passed_mode
-      || promoted_nominal_mode != data->promoted_mode)
+  if (need_conversion)
+    {
+      enum insn_code icode;
+      rtx op0, op1;
+
+      icode = can_extend_p (promoted_nominal_mode, data->passed_mode,
+			    unsignedp);
+
+      op0 = parmreg;
+      op1 = validated_mem;
+      if (icode != CODE_FOR_nothing
+	  && insn_data[icode].operand[0].predicate (op0, promoted_nominal_mode)
+	  && insn_data[icode].operand[1].predicate (op1, data->passed_mode))
+	{
+	  enum rtx_code code = unsignedp ? ZERO_EXTEND : SIGN_EXTEND;
+	  rtx insn;
+
+	  insn = gen_extend_insn (op0, op1, promoted_nominal_mode,
+				  data->passed_mode, unsignedp);
+	  emit_insn (insn);
+
+	  equiv_stack_parm = gen_rtx_fmt_e (code, GET_MODE (parmreg),
+					    equiv_stack_parm);
+	  moved = true;
+	}
+    }
+
+  if (moved)
+    /* Nothing to do.  */
+    ;
+  else if (need_conversion)
     {
       int save_tree_used;
 
@@ -2919,7 +2957,7 @@ assign_parm_setup_reg (struct assign_par
 
       rtx tempreg = gen_reg_rtx (GET_MODE (data->entry_parm));
 
-      emit_move_insn (tempreg, validize_mem (data->entry_parm));
+      emit_move_insn (tempreg, validated_mem);
 
       push_to_sequence2 (all->first_conversion_insn, all->last_conversion_insn);
       tempreg = convert_to_mode (data->nominal_mode, tempreg, unsignedp);
@@ -2949,7 +2987,7 @@ assign_parm_setup_reg (struct assign_par
       did_conversion = true;
     }
   else
-    emit_move_insn (parmreg, validize_mem (data->entry_parm));
+    emit_move_insn (parmreg, validated_mem);
 
   /* If we were passed a pointer but the actual value can safely live
      in a register, put it in one.  */
@@ -3034,7 +3072,7 @@ assign_parm_setup_reg (struct assign_par
 	}
       else if ((set = single_set (linsn)) != 0
 	       && SET_DEST (set) == parmreg)
-	set_unique_reg_note (linsn, REG_EQUIV, data->stack_parm);
+	set_unique_reg_note (linsn, REG_EQUIV, equiv_stack_parm);
     }
 
   /* For pointer data type, suggest pointer register.  */