(janet-lang#667) Add constant inlining for tuples and structs.

Structs and tuples composed entirely out of constant values
will themselves be considered constant values during compilation.
This reduces the amount of generated code.

src/core/compile.c

@@ -504,10 +504,40 @@ static JanetSlot janetc_call(JanetFopts opts, JanetSlot *slots, JanetSlot fun) {
 static JanetSlot janetc_maker(JanetFopts opts, JanetSlot *slots, int op) {
     JanetCompiler *c = opts.compiler;
     JanetSlot retslot;
-    janetc_pushslots(c, slots);
-    janetc_freeslots(c, slots);
-    retslot = janetc_gettarget(opts);
-    janetc_emit_s(c, op, retslot, 1);
+
+    /* Check if this structure is composed entirely of constants */
+    int can_inline = 1;
+    for (int32_t i = 0; i < janet_v_count(slots); i++) {
+        if (!(slots[i].flags & JANET_SLOT_CONSTANT) ||
+                (slots[i].flags & JANET_SLOT_SPLICED)) {
+            can_inline = 0;
+            break;
+        }
+    }
+
+    if (can_inline && (op == JOP_MAKE_STRUCT)) {
+        JanetKV *st = janet_struct_begin(janet_v_count(slots) / 2);
+        for (int32_t i = 0; i < janet_v_count(slots); i += 2) {
+            Janet k = slots[i].constant;
+            Janet v = slots[i + 1].constant;
+            janet_struct_put(st, k, v);
+        }
+        retslot = janetc_cslot(janet_wrap_struct(janet_struct_end(st)));
+        janetc_freeslots(c, slots);
+    } else if (can_inline && (op == JOP_MAKE_TUPLE)) {
+        Janet *tup = janet_tuple_begin(janet_v_count(slots));
+        for (int32_t i = 0; i < janet_v_count(slots); i++) {
+            tup[i] = slots[i].constant;
+        }
+        retslot = janetc_cslot(janet_wrap_tuple(janet_tuple_end(tup)));
+        janetc_freeslots(c, slots);
+    } else {
+        janetc_pushslots(c, slots);
+        janetc_freeslots(c, slots);
+        retslot = janetc_gettarget(opts);
+        janetc_emit_s(c, op, retslot, 1);
+    }
+
     return retslot;
 }