stage1 实现并修复ast2ir的核心功能的正确性

stage1/spl_ir.c

@@ -315,12 +315,16 @@ static spl_ir_node_ref_t builder_alloc_node(spl_ir_builder_t *b, spl_ir_kind_t k
     spl_ir_node_t *n = spl_ir_node(&b->ir, b->current_fn, ref);
     n->kind = kind;
     n->dbg = b->dbg;
-    if (b->current_block < vec_size(b->blocks)) {
-        vec_at(b->blocks, b->current_block) = ref;
-    } else {
+
+    if (b->current_block >= vec_size(b->blocks)) {
         Panic("unknown bblock");
         return 0;
     }
+
+    spl_ir_node_ref_t *slot = &vec_at(b->blocks, b->current_block);
+    if (*slot == 0)
+        *slot = ref;
+
     return ref;
 }
 
@@ -378,7 +382,7 @@ void spl_ir_builder_fn_end(spl_ir_builder_t *b) {
             target = vec_at(b->blocks, fx->block);
         }
         if (target == 0) {
-            Panic("unknown reloc target bblock");
+            Panic("reloc to empty/unknown bblock #%zu", fx->block);
         }
         switch (fx->slot) {
         case SPL_IR_FIX_BR_TRUE:
@@ -411,6 +415,10 @@ void spl_ir_builder_block_end(spl_ir_builder_t *b) {
     if (!b->terminated) {
         Panic("bblock must be end of terminated");
     }
+    if (b->current_block != 0 && b->current_block < vec_size(b->blocks) &&
+        vec_at(b->blocks, b->current_block) == 0) {
+        Panic("bblock #%zu is empty (no entry node emitted)", b->current_block);
+    }
 }
 
 #define X(name, kind)                                                                              \
@@ -769,7 +777,9 @@ spl_ir_node_ref_t spl_ir_builder_control_ret(spl_ir_builder_t *b, spl_type_id_t
 }
 
 spl_ir_node_ref_t spl_ir_builder_control_unreachable(spl_ir_builder_t *b) {
-    return builder_alloc_node(b, SPL_IR_CONTROL_UNREACHABLE);
+    spl_ir_node_ref_t ref = builder_alloc_node(b, SPL_IR_CONTROL_UNREACHABLE);
+    b->terminated = true;
+    return ref;
 }
 
 spl_ir_node_ref_t spl_ir_builder_control_trap(spl_ir_builder_t *b) {