Merge pull request #1307 from ziglang/cancel-semantics

improved coroutine cancel semantics
ziglang · Jul 30, 2018 · 5d4a02c · 5d4a02c
2 parents 608ff52 + cfe03c7
commit 5d4a02c
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Showing 10 changed files with 486 additions and 142 deletions.
diff --git a/doc/langref.html.in b/doc/langref.html.in
@@ -4665,24 +4665,24 @@ async fn testSuspendBlock() void {
       block, while the old thread continued executing the suspend block.
       </p>
       <p>
-      However, if you use labeled <code>break</code> on the suspend block, the coroutine
+      However, the coroutine can be directly resumed from the suspend block, in which case it
       never returns to its resumer and continues executing.
       </p>
       {#code_begin|test#}
 const std = @import("std");
 const assert = std.debug.assert;
 
-test "break from suspend" {
+test "resume from suspend" {
     var buf: [500]u8 = undefined;
     var a = &std.heap.FixedBufferAllocator.init(buf[0..]).allocator;
     var my_result: i32 = 1;
-    const p = try async<a> testBreakFromSuspend(&my_result);
+    const p = try async<a> testResumeFromSuspend(&my_result);
     cancel p;
     std.debug.assert(my_result == 2);
 }
-async fn testBreakFromSuspend(my_result: *i32) void {
-    s: suspend |p| {
-        break :s;
+async fn testResumeFromSuspend(my_result: *i32) void {
+    suspend |p| {
+        resume p;
     }
     my_result.* += 1;
     suspend;
@@ -7336,7 +7336,7 @@ Defer(body) = ("defer" | "deferror") body
 
 IfExpression(body) = "if" "(" Expression ")" body option("else" BlockExpression(body))
 
-SuspendExpression(body) = option(Symbol ":") "suspend" option(("|" Symbol "|" body))
+SuspendExpression(body) = "suspend" option(("|" Symbol "|" body))
 
 IfErrorExpression(body) = "if" "(" Expression ")" option("|" option("*") Symbol "|") body "else" "|" Symbol "|" BlockExpression(body)
 

diff --git a/src/all_types.hpp b/src/all_types.hpp
@@ -60,7 +60,7 @@ struct IrExecutable {
     ZigList<Tld *> tld_list;
 
     IrInstruction *coro_handle;
-    IrInstruction *coro_awaiter_field_ptr; // this one is shared and in the promise
+    IrInstruction *atomic_state_field_ptr; // this one is shared and in the promise
     IrInstruction *coro_result_ptr_field_ptr;
     IrInstruction *coro_result_field_ptr;
     IrInstruction *await_handle_var_ptr; // this one is where we put the one we extracted from the promise
@@ -898,7 +898,6 @@ struct AstNodeAwaitExpr {
 };
 
 struct AstNodeSuspend {
-    Buf *name;
     AstNode *block;
     AstNode *promise_symbol;
 };
@@ -1929,7 +1928,6 @@ struct ScopeLoop {
 struct ScopeSuspend {
     Scope base;
 
-    Buf *name;
     IrBasicBlock *resume_block;
     bool reported_err;
 };
@@ -3245,7 +3243,7 @@ static const size_t stack_trace_ptr_count = 30;
 #define RESULT_FIELD_NAME "result"
 #define ASYNC_ALLOC_FIELD_NAME "allocFn"
 #define ASYNC_FREE_FIELD_NAME "freeFn"
-#define AWAITER_HANDLE_FIELD_NAME "awaiter_handle"
+#define ATOMIC_STATE_FIELD_NAME "atomic_state"
 // these point to data belonging to the awaiter
 #define ERR_RET_TRACE_PTR_FIELD_NAME "err_ret_trace_ptr"
 #define RESULT_PTR_FIELD_NAME "result_ptr"

diff --git a/src/analyze.cpp b/src/analyze.cpp
@@ -161,7 +161,6 @@ ScopeSuspend *create_suspend_scope(AstNode *node, Scope *parent) {
     assert(node->type == NodeTypeSuspend);
     ScopeSuspend *scope = allocate<ScopeSuspend>(1);
     init_scope(&scope->base, ScopeIdSuspend, node, parent);
-    scope->name = node->data.suspend.name;
     return scope;
 }
 
@@ -519,11 +518,11 @@ TypeTableEntry *get_promise_frame_type(CodeGen *g, TypeTableEntry *return_type)
         return return_type->promise_frame_parent;
     }
 
-    TypeTableEntry *awaiter_handle_type = get_optional_type(g, g->builtin_types.entry_promise);
+    TypeTableEntry *atomic_state_type = g->builtin_types.entry_usize;
     TypeTableEntry *result_ptr_type = get_pointer_to_type(g, return_type, false);
 
     ZigList<const char *> field_names = {};
-    field_names.append(AWAITER_HANDLE_FIELD_NAME);
+    field_names.append(ATOMIC_STATE_FIELD_NAME);
     field_names.append(RESULT_FIELD_NAME);
     field_names.append(RESULT_PTR_FIELD_NAME);
     if (g->have_err_ret_tracing) {
@@ -533,7 +532,7 @@ TypeTableEntry *get_promise_frame_type(CodeGen *g, TypeTableEntry *return_type)
     }
 
     ZigList<TypeTableEntry *> field_types = {};
-    field_types.append(awaiter_handle_type);
+    field_types.append(atomic_state_type);
     field_types.append(return_type);
     field_types.append(result_ptr_type);
     if (g->have_err_ret_tracing) {
@@ -6228,7 +6227,12 @@ uint32_t get_abi_alignment(CodeGen *g, TypeTableEntry *type_entry) {
     } else if (type_entry->id == TypeTableEntryIdOpaque) {
         return 1;
     } else {
-        return LLVMABIAlignmentOfType(g->target_data_ref, type_entry->type_ref);
+        uint32_t llvm_alignment = LLVMABIAlignmentOfType(g->target_data_ref, type_entry->type_ref);
+        // promises have at least alignment 8 so that we can have 3 extra bits when doing atomicrmw
+        if (type_entry->id == TypeTableEntryIdPromise && llvm_alignment < 8) {
+            return 8;
+        }
+        return llvm_alignment;
     }
 }