+/* Helper for adjust_mems. Return 1 if *loc is unsuitable for
+ transformation of wider mode arithmetics to narrower mode,
+ -1 if it is suitable and subexpressions shouldn't be
+ traversed and 0 if it is suitable and subexpressions should
+ be traversed. Called through for_each_rtx. */
+
+static int
+use_narrower_mode_test (rtx *loc, void *data)
+{
+ rtx subreg = (rtx) data;
+
+ if (CONSTANT_P (*loc))
+ return -1;
+ switch (GET_CODE (*loc))
+ {
+ case REG:
+ if (cselib_lookup (*loc, GET_MODE (SUBREG_REG (subreg)), 0))
+ return 1;
+ return -1;
+ case PLUS:
+ case MINUS:
+ case MULT:
+ return 0;
+ case ASHIFT:
+ if (for_each_rtx (&XEXP (*loc, 0), use_narrower_mode_test, data))
+ return 1;
+ else
+ return -1;
+ default:
+ return 1;
+ }
+}
+
+/* Transform X into narrower mode MODE from wider mode WMODE. */
+
+static rtx
+use_narrower_mode (rtx x, enum machine_mode mode, enum machine_mode wmode)
+{
+ rtx op0, op1;
+ if (CONSTANT_P (x))
+ return lowpart_subreg (mode, x, wmode);
+ switch (GET_CODE (x))
+ {
+ case REG:
+ return lowpart_subreg (mode, x, wmode);
+ case PLUS:
+ case MINUS:
+ case MULT:
+ op0 = use_narrower_mode (XEXP (x, 0), mode, wmode);
+ op1 = use_narrower_mode (XEXP (x, 1), mode, wmode);
+ return simplify_gen_binary (GET_CODE (x), mode, op0, op1);
+ case ASHIFT:
+ op0 = use_narrower_mode (XEXP (x, 0), mode, wmode);
+ return simplify_gen_binary (ASHIFT, mode, op0, XEXP (x, 1));
+ default:
+ gcc_unreachable ();
+ }
+}
+