PR 68393: Handle SUBREG_PROMOTED_VAR_P in expand_direct_optab_fn

Do the usual dance when assigning to SUBREG_PROMOTED_VAR_P destinations:
first convert to the outer mode, then extend to the inner mode.

Tested that it fixes the powerpc64le-linux-gnu breakage.  Also tested
on x86_64-linux-gnu and powerpc64-linux-gnu.

gcc/
	PR bootstrap/68393
	* internal-fn.c (expand_direct_optab_fn): Handle SUBREG_PROMOTED_VAR_P
	destinations.

From-SVN: r230590

gcc/ChangeLog

+2015-11-19  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR bootstrap/68393
+	* internal-fn.c (expand_direct_optab_fn): Handle SUBREG_PROMOTED_VAR_P
+	destinations.
+
 2015-11-18  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/68198

gcc/internal-fn.c

@@ -2124,14 +2124,30 @@ expand_direct_optab_fn (internal_fn fn, gcall *stmt, direct_optab optab,
   expand_insn (icode, nargs + 1, ops);
   if (!rtx_equal_p (lhs_rtx, ops[0].value))
     {
-      if (INTEGRAL_TYPE_P (lhs_type))
-	/* Convert the operand to the required type, which is useful
-	   for things that return an int regardless of the size of
-	   the input.  If the value produced by the instruction is
-	   smaller than required, assume that it is signed.  */
-	convert_move (lhs_rtx, ops[0].value, 0);
-      else
+      /* If the return value has an integral type, convert the instruction
+	 result to that type.  This is useful for things that return an
+	 int regardless of the size of the input.  If the instruction result
+	 is smaller than required, assume that it is signed.
+
+	 If the return value has a nonintegral type, its mode must match
+	 the instruction result.  */
+      if (GET_CODE (lhs_rtx) == SUBREG && SUBREG_PROMOTED_VAR_P (lhs_rtx))
+	{
+	  /* If this is a scalar in a register that is stored in a wider
+	     mode than the declared mode, compute the result into its
+	     declared mode and then convert to the wider mode.  */
+	  gcc_checking_assert (INTEGRAL_TYPE_P (lhs_type));
+	  rtx tmp = convert_to_mode (GET_MODE (lhs_rtx), ops[0].value, 0);
+	  convert_move (SUBREG_REG (lhs_rtx), tmp,
+			SUBREG_PROMOTED_SIGN (lhs_rtx));
+	}
+      else if (GET_MODE (lhs_rtx) == GET_MODE (ops[0].value))
 	emit_move_insn (lhs_rtx, ops[0].value);
+      else
+	{
+	  gcc_checking_assert (INTEGRAL_TYPE_P (lhs_type));
+	  convert_move (lhs_rtx, ops[0].value, 0);
+	}
     }
 }