tcg/optimize: Use fold_masks_s in fold_not

Avoid the use of the OptContext slots.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/tcg/optimize.c b/tcg/optimize.c
index acff398..4ede218 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -2073,12 +2073,7 @@
     if (fold_const1(ctx, op)) {
         return true;
     }
-
-    ctx->s_mask = arg_info(op->args[1])->s_mask;
-
-    /* Because of fold_to_not, we want to always return true, via finish. */
-    finish_folding(ctx, op);
-    return true;
+    return fold_masks_s(ctx, op, arg_info(op->args[1])->s_mask);
 }
 
 static bool fold_or(OptContext *ctx, TCGOp *op)