From 1551bf6b48b0de1d2f544cbba1c60d09274a0f9e Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Tue, 13 Feb 2018 16:14:55 -0500
Subject: [PATCH] Use flatter representation for function and environments.

---
 src/core/bytecode.c        |  4 ++--
 src/core/fiber.c           |  1 +
 src/core/gc.c              | 11 ++++------
 src/core/vm.c              | 44 ++++++++++++++++----------------------
 src/include/dst/dsttypes.h |  3 +--
 5 files changed, 27 insertions(+), 36 deletions(-)

diff --git a/src/core/bytecode.c b/src/core/bytecode.c
index f16ceeee..b199ce15 100644
--- a/src/core/bytecode.c
+++ b/src/core/bytecode.c
@@ -217,7 +217,7 @@ DstFuncDef *dst_funcdef_alloc() {
     def->defs_length = 0;
     def->constants_length = 0;
     def->bytecode_length = 0;
-    def->environments_length = 1;
+    def->environments_length = 0;
     return def;
 }
 
@@ -225,7 +225,7 @@ DstFuncDef *dst_funcdef_alloc() {
 DstFunction *dst_thunk(DstFuncDef *def) {
     DstFunction *func = dst_gcalloc(DST_MEMORY_FUNCTION, sizeof(DstFunction));
     func->def = def;
-    func->envs = NULL;
+    dst_assert(def->environments_length == 0, "tried to create thunk that needs upvalues");
     return func;
 }
 
diff --git a/src/core/fiber.c b/src/core/fiber.c
index 096fbe6f..f6971a5f 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -230,6 +230,7 @@ void dst_fiber_cframe(DstFiber *fiber) {
     newframe->prevframe = oldframe;
     newframe->pc = NULL;
     newframe->func = NULL;
+    newframe->env = NULL;
 }
 
 /* Pop a stack frame from the fiber. Returns the new stack frame, or
diff --git a/src/core/gc.c b/src/core/gc.c
index 5a06e623..f0fc2b55 100644
--- a/src/core/gc.c
+++ b/src/core/gc.c
@@ -166,10 +166,9 @@ static void dst_mark_function(DstFunction *func) {
         return;
     dst_gc_mark(func);
     numenvs = func->def->environments_length;
-    if (NULL != func->envs)
-        for (i = 0; i < numenvs; ++i)
-            if (NULL != func->envs[i])
-                dst_mark_funcenv(func->envs[i]);
+    for (i = 0; i < numenvs; ++i) {
+        dst_mark_funcenv(func->envs[i]);
+    }
     dst_mark_funcdef(func->def);
 }
 
@@ -204,6 +203,7 @@ static void dst_deinit_block(DstGCMemoryHeader *block) {
     DstAbstractHeader *h = (DstAbstractHeader *)mem;
     switch (block->flags & DST_MEM_TYPEBITS) {
         default:
+        case DST_MEMORY_FUNCTION:
             break; /* Do nothing for non gc types */ 
         case DST_MEMORY_SYMBOL:
             dst_symbol_deinit((const uint8_t *)mem + 2 * sizeof(int32_t));
@@ -220,9 +220,6 @@ static void dst_deinit_block(DstGCMemoryHeader *block) {
         case DST_MEMORY_BUFFER:
             dst_buffer_deinit((DstBuffer *) mem);
             break; 
-        case DST_MEMORY_FUNCTION:
-            free(((DstFunction *)mem)->envs);
-            break;
         case DST_MEMORY_ABSTRACT:
             if (h->type->gc) {
                 if (h->type->gc((void *)(h + 1), h->size)) {
diff --git a/src/core/vm.c b/src/core/vm.c
index 9e182125..eac74571 100644
--- a/src/core/vm.c
+++ b/src/core/vm.c
@@ -495,36 +495,30 @@ static void *op_lookup[255] = {
     {
         DstFuncDef *fd;
         DstFunction *fn;
+        int32_t elen;
         vm_assert((int32_t)oparg(2, 0xFFFF) < func->def->defs_length, "invalid funcdef");
         fd = func->def->defs[(int32_t)oparg(2, 0xFFFF)];
-        fn = dst_thunk(fd);
+        elen = fd->environments_length;
+        fn = dst_gcalloc(DST_MEMORY_FUNCTION, sizeof(DstFunction) + (elen * sizeof(DstFuncEnv *)));
+        fn->def = fd;
         {
-            int32_t elen = fd->environments_length;
-            if (elen) {
-                int32_t i;
-                fn->envs = malloc(sizeof(DstFuncEnv *) * elen);
-                if (NULL == fn->envs) {
-                    DST_OUT_OF_MEMORY;
-                }
-                for (i = 0; i < elen; ++i) {
-                    int32_t inherit = fd->environments[i];
-                    if (inherit == -1) {
-                        DstStackFrame *frame = (DstStackFrame *)stack - 1;
-                        if (!frame->env) {
-                            /* Lazy capture of current stack frame */
-                            DstFuncEnv *env = dst_gcalloc(DST_MEMORY_FUNCENV, sizeof(DstFuncEnv));
-                            env->offset = dst_vm_fiber->frame;
-                            env->as.fiber = dst_vm_fiber;
-                            env->length = func->def->slotcount;
-                            frame->env = env;
-                        }
-                        fn->envs[i] = frame->env;
-                    } else {
-                        fn->envs[i] = func->envs[inherit];
+            int32_t i;
+            for (i = 0; i < elen; ++i) {
+                int32_t inherit = fd->environments[i];
+                if (inherit == -1) {
+                    DstStackFrame *frame = (DstStackFrame *)stack - 1;
+                    if (!frame->env) {
+                        /* Lazy capture of current stack frame */
+                        DstFuncEnv *env = dst_gcalloc(DST_MEMORY_FUNCENV, sizeof(DstFuncEnv));
+                        env->offset = dst_vm_fiber->frame;
+                        env->as.fiber = dst_vm_fiber;
+                        env->length = func->def->slotcount;
+                        frame->env = env;
                     }
+                    fn->envs[i] = frame->env;
+                } else {
+                    fn->envs[i] = func->envs[inherit];
                 }
-            } else {
-                fn->envs = NULL;
             }
         }
         stack[oparg(1, 0xFF)] = dst_wrap_function(fn);
diff --git a/src/include/dst/dsttypes.h b/src/include/dst/dsttypes.h
index 2b668039..ba610524 100644
--- a/src/include/dst/dsttypes.h
+++ b/src/include/dst/dsttypes.h
@@ -402,8 +402,7 @@ struct DstFuncEnv {
 /* A function */
 struct DstFunction {
     DstFuncDef *def;
-    /* Consider allocating envs with entire function struct */
-    DstFuncEnv **envs;
+    DstFuncEnv *envs[];
 };
 
 /* Defines an abstract type */