Fix calculation of labels and jump destinations.

Previously, all calculations regarding stack depth and label depth
were broken. *All* of them. Off-by-ones, the logic was wrong, etc.
Variables are still screwed up, but I'm *almost* there, where
"there" is being able to generate functioning programs, hopefully?

src/format.c

@@ -120,6 +120,7 @@ symbol new_symbol(void) {
 
 void define_executable_symbol(symbol s) {
     struct symbol* sym = &symbols[s];
+    assert(sym->vaddr == (uint64_t) -1);
     sym->vaddr = file_here;
 }
 

src/ir.c

@@ -38,10 +38,7 @@ static uint32_t label_depth = 0;
 static struct label labels[MAX_LABELS];
 
 void init_ir(var* argc, var* argv, var* env) {
-    assert(stack_depth == 0);
-    // seems like this should be necessary. it really feels like there's some
-    // off-by-one arrows going on around here, but I can't figure it out.
-    //enter();
+    assert(stack_depth == 0 && stack_frame == 0);
     x86_inst_mov_r64_r64(BP, SP);
     x86_inst_add_r64_imm8(BP, 8 * 3);
     *env = stack_depth++;
@@ -51,7 +48,8 @@ void init_ir(var* argc, var* argv, var* env) {
 
 void enter(void) {
     assert(stack_frame < MAX_STACK_FRAMES);
-    struct stack_frame frame = { stack_depth, label_depth };
+    printf("ENTERING: %i, %i\n", stack_depth, label_depth);
+    struct stack_frame frame = { .depth = stack_depth, .label_depth = label_depth };
     stack_frames[stack_frame] = frame;
     stack_frame++;
     // exit label
@@ -61,15 +59,16 @@ void enter(void) {
 void leave(var* args) {
     assert(stack_frame > 0);
     struct stack_frame frame = stack_frames[stack_frame - 1];
-    stack_frame--;
     stack_depth = frame.depth;
+    label_depth = frame.label_depth;
     define(frame.label_depth, args);
+    stack_frame--;
 }
 
 label declare(uint32_t argc) {
     assert(label_depth < MAX_LABELS);
     symbol sym = new_symbol();
-    struct label label = { stack_frame, argc, sym };
+    struct label label = { .frame = stack_frame, .argc = argc, .symbol = sym };
     labels[label_depth] = label;
     return label_depth++;
 }
@@ -82,18 +81,13 @@ label declare_exit(uint32_t argc) {
 
 void define(label l, var* args) {
     struct label* label = &labels[l];
+    printf("DEFINING %i (%i)\n", l, label->argc);
     define_executable_symbol(label->symbol);
-    // possibly wrong. do I need to do any clean-up of the old frame here?
-    stack_frame = label->frame;
-    struct stack_frame* frame = &stack_frames[stack_frame - 1];
-    label_depth = frame->label_depth;
+    assert(label->frame == stack_frame);
     for (uint32_t i = 0; i < label->argc; i++) {
-        args[i] = frame->depth + i;
+        args[i] = stack_depth + i;
     }
-    // probably wrong. seems like I ought to create a new frame or something?
-    // wouldn't this make the old frame too deep?
-    // but on the other hand, if I enter a new frame, how do I decide when to leave it?
-    frame->depth += label->argc;
+    stack_depth += label->argc;
 }
 
 void load_var(reg reg, var var) {
@@ -109,13 +103,11 @@ var push_var(reg reg) {
 }
 
 void load_args(struct label* label, var* args) {
-    struct stack_frame* cur_frame = &stack_frames[stack_frame - 1];
     struct stack_frame* dest_frame = &stack_frames[label->frame];
-    uint32_t depth_diff = cur_frame->depth - dest_frame->depth;
+    uint32_t depth_diff = stack_depth - dest_frame->depth;
     if (depth_diff > 0) {
         // FIXME: should be immX!!!
-        // FIXME: this should be necessary! stack depth is never getting decreased!
-        //x86_inst_add_r64_imm8(SP, depth_diff);
+        x86_inst_add_r64_imm8(SP, depth_diff);
     }
     for (uint32_t arg = 0; arg < label->argc; arg++) {
         load_var(AX, args[arg]);
@@ -125,6 +117,7 @@ void load_args(struct label* label, var* args) {
 
 void jump(label l, var* args) {
     struct label* label = &labels[l];
+    printf("JUMP %i (%i)\n", l, label->argc);
     load_args(label, args);
     inst_jump(label->symbol);
 }
@@ -135,6 +128,7 @@ void jump_table(size_t branches, label* labels, var index, var* args) {
 
 void jump_if(label l, var cond, var* args) {
     struct label* label = &labels[l];
+    printf("JUMP_IF %i (%i)\n", l, label->argc);
     load_var(BX, cond);
     load_args(label, args);
     inst_jump_if_not_zero(label->symbol, BX);
@@ -142,6 +136,7 @@ void jump_if(label l, var cond, var* args) {
 
 void jump_unless(label l, var cond, var* args) {
     struct label* label = &labels[l];
+    printf("JUMP_UNLESS %i (%i)\n", l, label->argc);
     load_var(BX, cond);
     load_args(label, args);
     inst_jump_if_zero(label->symbol, BX);

src/lang.c

@@ -34,6 +34,7 @@ enum if_state {
     IF_COND,
     IF_THEN,
     IF_ELSE,
+    IF_END,
 };
 
 struct if_crumb {
@@ -336,6 +337,7 @@ void enter_block(void) {
             struct if_crumb ifc = ctx->data.if_;
             switch (ifc.state) {
                 case IF_COND:
+                case IF_END:
                     assert(0);
                 case IF_THEN:
                     define(ifc.then, NULL);
@@ -351,6 +353,7 @@ void enter_block(void) {
             assert(loopc->state == LOOP_CLEAN);
             loopc->state = LOOP_BODY;
             loopc->next = declare(loopc->assignment_count);
+            printf("LOOP %i END %i\n", loopc->next, loopc->exit);
             var args[MAX_ASSIGNMENTS];
             define(loopc->next, args);
             // TODO NOTE: is this the correct order?
@@ -392,9 +395,9 @@ void stmt_expr(void) {
 
 void exit_block(void) {
     printf("** exit_block\n");
-    struct crumb ctx = context[context_depth - 1];
-    assert(ctx.type == BLOCK_CRUMB);
-    struct block_crumb blockc = ctx.data.block;
+    struct crumb* ctx = &context[context_depth - 1];
+    assert(ctx->type == BLOCK_CRUMB);
+    struct block_crumb blockc = ctx->data.block;
     assert(blockc.state == BLOCK_CLEAN);
     var ret = blockc.final;
     if (ret == (var) -1) {
@@ -402,21 +405,26 @@ void exit_block(void) {
         ret = lit(0);
     }
     context_depth--;
-    ctx = context[context_depth - 1];
-    switch (ctx.type) {
+    ctx = &context[context_depth - 1];
+    switch (ctx->type) {
         case EXPR_CRUMB: {
             push_argument(ret);
             break;
         }
         case IF_CRUMB: {
-            struct if_crumb ifc = ctx.data.if_;
-            assert(ifc.state != IF_COND);
-            jump(ifc.end, &ret);
+            struct if_crumb* ifc = &ctx->data.if_;
+            assert(ifc->state == IF_THEN || ifc->state == IF_ELSE);
+            jump(ifc->end, &ret);
+            if (ifc->state == IF_THEN) {
+                ifc->state = IF_ELSE;
+            } else if (ifc->state == IF_ELSE) {
+                ifc->state = IF_END;
+            }
             break;
         }
         case LOOP_CRUMB: {
             // unlike with `if`, there is no `exit_loop`, so we do clean-up here.
-            struct loop_crumb loopc = ctx.data.loop;
+            struct loop_crumb loopc = ctx->data.loop;
             assert(loopc.state == LOOP_BODY);
             jump(loopc.exit, &ret);
             context_depth--;
@@ -501,6 +509,7 @@ void enter_if(void) {
     label then = declare(0);
     label else_ = declare(0);
     label end = declare_exit(1);
+    printf("IF THEN %i ELSE %i EXIT %i\n", then, else_, end);
     struct if_crumb ifc = {
         .state = IF_COND,
         .then = then,
@@ -524,14 +533,15 @@ void exit_if(void) {
     struct if_crumb ifc = ctx.data.if_;
     switch (ifc.state) {
         case IF_COND:
+        case IF_THEN:
             assert(0);
-        case IF_THEN: {
+        case IF_ELSE: {
             define(ifc.else_, NULL);
             var ret = lit(0);
             jump(ifc.end, &ret);
             break;
         }
-        case IF_ELSE:
+        case IF_END:
             break;
     }
     var ret;