Skip to content

Commit

Permalink
labeled blocks and loops
Browse files Browse the repository at this point in the history 
New syntax:

    (block $foo <expr>*)
    (loop $exit <expr>*)
    (loop $exit $cont <expr>*)

The labels are optional, and if not specified they will not "count".
That is, a numeric break will skip over them:

    (block $here
      (block
        (block
          (break 0))))  ;; goes to $here

Note this is only true for blocks and loops; unnamed labels are
"anonymous," and can only be referenced numerically:

    (label (break 0))

An additional change is that the label statement no longer has an
implicit block, so this is illegal:

    (label $foo (nop) (nop))
  • Loading branch information
@binji
binji committed Oct 13, 2015
1 parent 4200ec1 commit 7601228
Show file tree
Hide file tree
Showing 24 changed files with 510 additions and 123 deletions.
111 changes: 84 additions & 27 deletions src/wasm-gen.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -62,9 +62,10 @@ typedef struct OutputBuffer {
} OutputBuffer;

typedef struct LabelInfo {
struct LabelInfo* next_label;
uint32_t offset;
int block_depth;
struct LabelInfo* next_label;
int with_expr;
} LabelInfo;

typedef struct Context {
Expand Down Expand Up @@ -516,6 +517,23 @@ static void remap_locals(Context* ctx, WasmFunction* function) {
}
}

static LabelInfo* push_label_info(Context* ctx) {
LabelInfo* label_info = malloc(sizeof(LabelInfo));
label_info->offset = ctx->buf.size;
label_info->block_depth = ctx->block_depth++;
label_info->next_label = ctx->top_label;
label_info->with_expr = 0;
ctx->top_label = label_info;
return label_info;
}

static void pop_label_info(Context* ctx) {
LabelInfo* label_info = ctx->top_label;
ctx->block_depth--;
ctx->top_label = label_info->next_label;
free(label_info);
}

static void before_module(WasmModule* module, void* user_data) {
Context* ctx = user_data;
ctx->function_header_offsets = realloc(
Expand Down Expand Up @@ -579,12 +597,18 @@ static void after_function(WasmModule* module,
ctx->buf.size, "FIXUP func code end offset");
}

static WasmParserCookie before_block(void* user_data) {
static WasmParserCookie before_block(int with_label, void* user_data) {
Context* ctx = user_data;
WasmParserCookie cookie = (WasmParserCookie)ctx->buf.size;
WasmParserCookie cookie = 0;
/* TODO(binji): clean this up, it's a bit hacky right now. */
if (with_label) {
push_label_info(ctx);
} else {
ctx->block_depth++;
cookie = (WasmParserCookie)ctx->buf.size;
}
out_opcode(&ctx->buf, WASM_OPCODE_BLOCK);
out_u8(&ctx->buf, 0, "num expressions");
ctx->block_depth++;
return cookie;
}

Expand All @@ -593,8 +617,14 @@ static void after_block(WasmType type,
WasmParserCookie cookie,
void* user_data) {
Context* ctx = user_data;
ctx->block_depth--;
uint32_t offset = (uint32_t)cookie;
uint32_t offset;
if (cookie == 0) {
offset = ctx->top_label->offset;
pop_label_info(ctx);
} else {
ctx->block_depth--;
offset = (uint32_t)cookie;
}
if (type != WASM_TYPE_VOID)
out_u8_at(&ctx->buf, offset, WASM_OPCODE_EXPR_BLOCK,
"FIXUP OPCODE_EXPR_BLOCK");
Expand All @@ -614,6 +644,7 @@ static WasmParserCookie before_break(int with_expr,
LabelInfo* label_info = ctx->top_label;
for (; label_depth > 0; label_depth--)
label_info = label_info->next_label;
label_info->with_expr = label_info->with_expr || with_expr;
int block_depth = (ctx->block_depth - 1) - label_info->block_depth;
out_u8(&ctx->buf, block_depth, "break depth");
return 0;
Expand Down Expand Up @@ -719,30 +750,21 @@ static void after_if(WasmType type,

static WasmParserCookie before_label(void* user_data) {
Context* ctx = user_data;
LabelInfo* label_info = malloc(sizeof(LabelInfo));
label_info->offset = ctx->buf.size;
label_info->block_depth = ctx->block_depth++;
label_info->next_label = ctx->top_label;
ctx->top_label = label_info;
push_label_info(ctx);
out_opcode(&ctx->buf, WASM_OPCODE_BLOCK);
out_u8(&ctx->buf, 0, "num expressions");
return (WasmParserCookie)label_info;
out_u8(&ctx->buf, 1, "num expressions");
return 0;
}

static void after_label(WasmType type,
int num_exprs,
WasmParserCookie cookie,
void* user_data) {
Context* ctx = user_data;
ctx->block_depth--;
LabelInfo* label_info = (LabelInfo*)cookie;
ctx->top_label = label_info->next_label;
uint32_t offset = label_info->offset;
free(label_info);
uint32_t offset = ctx->top_label->offset;
pop_label_info(ctx);
if (type != WASM_TYPE_VOID)
out_u8_at(&ctx->buf, offset, WASM_OPCODE_EXPR_BLOCK,
"FIXUP OPCODE_EXPR_BLOCK");
out_u8_at(&ctx->buf, offset + 1, num_exprs, "FIXUP num expressions");
}

static void before_load(enum WasmOpcode opcode,
Expand All @@ -759,22 +781,57 @@ static void after_load_global(int index, void* user_data) {
out_leb128(&ctx->buf, index, "global index");
}

static WasmParserCookie before_loop(void* user_data) {
static WasmParserCookie before_loop(int with_inner_label,
int with_outer_label,
void* user_data) {
Context* ctx = user_data;
out_opcode(&ctx->buf, WASM_OPCODE_LOOP);
WasmParserCookie cookie = (WasmParserCookie)ctx->buf.size;
out_u8(&ctx->buf, 0, "num expressions");
ctx->block_depth++;
WasmParserCookie cookie = 0;
/* TODO(binji): clean this up, it's a bit hacky right now. */
if (with_inner_label || with_outer_label) {
/* The outer label must be defined if the inner label is defined */
assert(with_outer_label);
push_label_info(ctx);
if (with_inner_label) {
/* The loop only has one expression: this nested block */
out_u8(&ctx->buf, 1, "num expressions");
out_opcode(&ctx->buf, WASM_OPCODE_BLOCK);
push_label_info(ctx);
out_u8(&ctx->buf, 0, "num expressions");
cookie = 1;
} else {
out_u8(&ctx->buf, 0, "num expressions");
}
} else {
cookie = (WasmParserCookie)ctx->buf.size;
out_u8(&ctx->buf, 0, "num expressions");
ctx->block_depth++;
}
return cookie;
}

static void after_loop(int num_exprs,
WasmParserCookie cookie,
void* user_data) {
Context* ctx = user_data;
ctx->block_depth--;
uint32_t offset = (uint32_t)cookie;
out_u8_at(&ctx->buf, offset, num_exprs, "FIXUP num expressions");
if (cookie == 0 || cookie == 1) {
LabelInfo* label_info = ctx->top_label;
out_u8_at(&ctx->buf, label_info->offset, num_exprs,
"FIXUP num expressions");
if (cookie == 1) {
/* inner and outer label */
if (label_info->with_expr)
out_u8_at(&ctx->buf, label_info->offset - 1, WASM_OPCODE_EXPR_BLOCK,
"FIXUP OPCODE_EXPR_BLOCK");
pop_label_info(ctx);
}
pop_label_info(ctx);
} else {
/* no labels */
ctx->block_depth--;
uint32_t offset = (uint32_t)cookie;
out_u8_at(&ctx->buf, offset, num_exprs, "FIXUP num expressions");
}
}

static void after_memory_size(void* user_data) {
Expand Down
Loading

0 comments on commit 7601228

Please sign in to comment.