Commit fbf21efd24

Andrew Kelley <andrew@ziglang.org>
2019-08-05 00:57:59
simpler, less memory intensive suspend/resume implementation
1 parent 042914d
src/all_types.hpp
@@ -1386,7 +1386,6 @@ struct ZigFn {
 
     ZigList<IrInstructionAllocaGen *> alloca_gen_list;
     ZigList<ZigVar *> variable_list;
-    ZigList<IrBasicBlock *> resume_blocks;
 
     Buf *section_name;
     AstNode *set_alignstack_node;
@@ -1719,6 +1718,7 @@ struct CodeGen {
     LLVMValueRef cur_async_resume_index_ptr;
     LLVMValueRef cur_async_awaiter_ptr;
     LLVMBasicBlockRef cur_preamble_llvm_block;
+    size_t cur_resume_block_count;
     LLVMValueRef cur_err_ret_trace_val_arg;
     LLVMValueRef cur_err_ret_trace_val_stack;
     LLVMValueRef memcpy_fn_val;
@@ -2114,7 +2114,6 @@ struct ScopeRuntime {
 struct ScopeSuspend {
     Scope base;
 
-    IrBasicBlock *resume_block;
     bool reported_err;
 };
 
@@ -2169,8 +2168,6 @@ struct IrBasicBlock {
     size_t ref_count;
     // index into the basic block list
     size_t index;
-    // for async functions, the resume index which corresponds to this block
-    size_t resume_index;
     LLVMBasicBlockRef llvm_block;
     LLVMBasicBlockRef llvm_exit_block;
     // The instruction that referenced this basic block and caused us to
@@ -2354,7 +2351,7 @@ enum IrInstructionId {
     IrInstructionIdPtrOfArrayToSlice,
     IrInstructionIdUnionInitNamedField,
     IrInstructionIdSuspendBegin,
-    IrInstructionIdSuspendBr,
+    IrInstructionIdSuspendFinish,
     IrInstructionIdAwait,
     IrInstructionIdCoroResume,
 };
@@ -3600,13 +3597,13 @@ struct IrInstructionPtrOfArrayToSlice {
 struct IrInstructionSuspendBegin {
     IrInstruction base;
 
-    IrBasicBlock *resume_block;
+    LLVMBasicBlockRef resume_bb;
 };
 
-struct IrInstructionSuspendBr {
+struct IrInstructionSuspendFinish {
     IrInstruction base;
 
-    IrBasicBlock *resume_block;
+    IrInstructionSuspendBegin *begin;
 };
 
 struct IrInstructionAwait {
@@ -3710,9 +3707,6 @@ static const size_t coro_resume_index = 1;
 static const size_t coro_awaiter_index = 2;
 static const size_t coro_arg_start = 3;
 
-// one for the Entry block, resume blocks are indexed after that.
-static const size_t coro_extra_resume_block_count = 1;
-
 // TODO call graph analysis to find out what this number needs to be for every function
 // MUST BE A POWER OF TWO.
 static const size_t stack_trace_ptr_count = 32;
src/codegen.cpp
@@ -3661,8 +3661,8 @@ static LLVMValueRef ir_render_call(CodeGen *g, IrExecutable *executable, IrInstr
         ZigType *ptr_result_type = get_pointer_to_type(g, src_return_type, true);
 
         LLVMBasicBlockRef call_bb = LLVMAppendBasicBlock(g->cur_fn_val, "CallResume");
-        size_t new_block_index = g->cur_fn->resume_blocks.length + coro_extra_resume_block_count;
-        g->cur_fn->resume_blocks.append(nullptr);
+        size_t new_block_index = g->cur_resume_block_count;
+        g->cur_resume_block_count += 1;
         LLVMValueRef new_block_index_val = LLVMConstInt(usize_type_ref, new_block_index, false);
         LLVMAddCase(g->cur_async_switch_instr, new_block_index_val, call_bb);
 
@@ -5153,15 +5153,22 @@ static LLVMValueRef ir_render_suspend_begin(CodeGen *g, IrExecutable *executable
         IrInstructionSuspendBegin *instruction)
 {
     LLVMTypeRef usize_type_ref = g->builtin_types.entry_usize->llvm_type;
-    LLVMValueRef new_resume_index = LLVMConstInt(usize_type_ref, instruction->resume_block->resume_index, false);
-    LLVMBuildStore(g->builder, new_resume_index, g->cur_async_resume_index_ptr);
+    instruction->resume_bb = LLVMAppendBasicBlock(g->cur_fn_val, "SuspendResume");
+    size_t new_block_index = g->cur_resume_block_count;
+    g->cur_resume_block_count += 1;
+    LLVMValueRef new_block_index_val = LLVMConstInt(usize_type_ref, new_block_index, false);
+    LLVMAddCase(g->cur_async_switch_instr, new_block_index_val, instruction->resume_bb);
+    LLVMBuildStore(g->builder, new_block_index_val, g->cur_async_resume_index_ptr);
     return nullptr;
 }
 
-static LLVMValueRef ir_render_suspend_br(CodeGen *g, IrExecutable *executable,
-        IrInstructionSuspendBr *instruction)
+static LLVMValueRef ir_render_suspend_finish(CodeGen *g, IrExecutable *executable,
+        IrInstructionSuspendFinish *instruction)
 {
     LLVMBuildRetVoid(g->builder);
+
+    LLVMPositionBuilderAtEnd(g->builder, instruction->begin->resume_bb);
+    render_async_var_decls(g, instruction->base.scope);
     return nullptr;
 }
 
@@ -5173,8 +5180,8 @@ static LLVMValueRef ir_render_await(CodeGen *g, IrExecutable *executable, IrInst
 
     // Prepare to be suspended
     LLVMBasicBlockRef resume_bb = LLVMAppendBasicBlock(g->cur_fn_val, "AwaitResume");
-    size_t new_block_index = g->cur_fn->resume_blocks.length + coro_extra_resume_block_count;
-    g->cur_fn->resume_blocks.append(nullptr);
+    size_t new_block_index = g->cur_resume_block_count;
+    g->cur_resume_block_count += 1;
     LLVMValueRef new_block_index_val = LLVMConstInt(usize_type_ref, new_block_index, false);
     LLVMAddCase(g->cur_async_switch_instr, new_block_index_val, resume_bb);
     LLVMBuildStore(g->builder, new_block_index_val, g->cur_async_resume_index_ptr);
@@ -5534,8 +5541,8 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
             return ir_render_ptr_of_array_to_slice(g, executable, (IrInstructionPtrOfArrayToSlice *)instruction);
         case IrInstructionIdSuspendBegin:
             return ir_render_suspend_begin(g, executable, (IrInstructionSuspendBegin *)instruction);
-        case IrInstructionIdSuspendBr:
-            return ir_render_suspend_br(g, executable, (IrInstructionSuspendBr *)instruction);
+        case IrInstructionIdSuspendFinish:
+            return ir_render_suspend_finish(g, executable, (IrInstructionSuspendFinish *)instruction);
         case IrInstructionIdCoroResume:
             return ir_render_coro_resume(g, executable, (IrInstructionCoroResume *)instruction);
         case IrInstructionIdFrameSizeGen:
@@ -5552,19 +5559,10 @@ static void ir_render(CodeGen *g, ZigFn *fn_entry) {
     IrExecutable *executable = &fn_entry->analyzed_executable;
     assert(executable->basic_block_list.length > 0);
 
-    if (fn_is_async(fn_entry)) {
-        IrBasicBlock *entry_block = executable->basic_block_list.at(0);
-        LLVMPositionBuilderAtEnd(g->builder, entry_block->llvm_block);
-        render_async_var_decls(g, entry_block->instruction_list.at(0)->scope);
-    }
-
     for (size_t block_i = 0; block_i < executable->basic_block_list.length; block_i += 1) {
         IrBasicBlock *current_block = executable->basic_block_list.at(block_i);
         assert(current_block->llvm_block);
         LLVMPositionBuilderAtEnd(g->builder, current_block->llvm_block);
-        if (current_block->resume_index != 0) {
-            render_async_var_decls(g, current_block->instruction_list.at(0)->scope);
-        }
         for (size_t instr_i = 0; instr_i < current_block->instruction_list.length; instr_i += 1) {
             IrInstruction *instruction = current_block->instruction_list.at(instr_i);
             if (instruction->ref_count == 0 && !ir_has_side_effects(instruction))
@@ -6757,6 +6755,8 @@ static void do_code_gen(CodeGen *g) {
         }
 
         if (is_async) {
+            g->cur_resume_block_count = 0;
+
             LLVMTypeRef usize_type_ref = g->builtin_types.entry_usize->llvm_type;
             LLVMValueRef size_val = LLVMConstInt(usize_type_ref, fn_table_entry->frame_type->abi_size, false);
             ZigLLVMFunctionSetPrefixData(fn_table_entry->llvm_value, size_val);
@@ -6777,19 +6777,15 @@ static void do_code_gen(CodeGen *g) {
             LLVMValueRef resume_index_ptr = LLVMBuildStructGEP(g->builder, g->cur_ret_ptr, coro_resume_index, "");
             g->cur_async_resume_index_ptr = resume_index_ptr;
             LLVMValueRef resume_index = LLVMBuildLoad(g->builder, resume_index_ptr, "");
-            LLVMValueRef switch_instr = LLVMBuildSwitch(g->builder, resume_index, bad_resume_block,
-                    fn_table_entry->resume_blocks.length + coro_extra_resume_block_count);
+            LLVMValueRef switch_instr = LLVMBuildSwitch(g->builder, resume_index, bad_resume_block, 4);
             g->cur_async_switch_instr = switch_instr;
 
             LLVMValueRef zero = LLVMConstNull(usize_type_ref);
-            LLVMAddCase(switch_instr, zero, executable->basic_block_list.at(0)->llvm_block);
-
-            for (size_t resume_i = 0; resume_i < fn_table_entry->resume_blocks.length; resume_i += 1) {
-                IrBasicBlock *resume_block = fn_table_entry->resume_blocks.at(resume_i);
-                LLVMValueRef case_value = LLVMConstInt(usize_type_ref, resume_block->resume_index, false);
-                LLVMAddCase(switch_instr, case_value, resume_block->llvm_block);
-            }
-
+            IrBasicBlock *entry_block = executable->basic_block_list.at(0);
+            LLVMAddCase(switch_instr, zero, entry_block->llvm_block);
+            g->cur_resume_block_count += 1;
+            LLVMPositionBuilderAtEnd(g->builder, entry_block->llvm_block);
+            render_async_var_decls(g, entry_block->instruction_list.at(0)->scope);
         } else {
             // create debug variable declarations for parameters
             // rely on the first variables in the variable_list being parameters.
src/ir.cpp
@@ -1049,8 +1049,8 @@ static constexpr IrInstructionId ir_instruction_id(IrInstructionSuspendBegin *)
     return IrInstructionIdSuspendBegin;
 }
 
-static constexpr IrInstructionId ir_instruction_id(IrInstructionSuspendBr *) {
-    return IrInstructionIdSuspendBr;
+static constexpr IrInstructionId ir_instruction_id(IrInstructionSuspendFinish *) {
+    return IrInstructionIdSuspendFinish;
 }
 
 static constexpr IrInstructionId ir_instruction_id(IrInstructionAwait *) {
@@ -3260,25 +3260,21 @@ static IrInstruction *ir_build_end_expr(IrBuilder *irb, Scope *scope, AstNode *s
     return &instruction->base;
 }
 
-static IrInstruction *ir_build_suspend_begin(IrBuilder *irb, Scope *scope, AstNode *source_node,
-        IrBasicBlock *resume_block)
-{
+static IrInstructionSuspendBegin *ir_build_suspend_begin(IrBuilder *irb, Scope *scope, AstNode *source_node) {
     IrInstructionSuspendBegin *instruction = ir_build_instruction<IrInstructionSuspendBegin>(irb, scope, source_node);
     instruction->base.value.type = irb->codegen->builtin_types.entry_void;
-    instruction->resume_block = resume_block;
-
-    ir_ref_bb(resume_block);
 
-    return &instruction->base;
+    return instruction;
 }
 
-static IrInstruction *ir_build_suspend_br(IrBuilder *irb, Scope *scope, AstNode *source_node,
-        IrBasicBlock *resume_block)
+static IrInstruction *ir_build_suspend_finish(IrBuilder *irb, Scope *scope, AstNode *source_node,
+        IrInstructionSuspendBegin *begin)
 {
-    IrInstructionSuspendBr *instruction = ir_build_instruction<IrInstructionSuspendBr>(irb, scope, source_node);
-    instruction->resume_block = resume_block;
+    IrInstructionSuspendFinish *instruction = ir_build_instruction<IrInstructionSuspendFinish>(irb, scope, source_node);
+    instruction->base.value.type = irb->codegen->builtin_types.entry_void;
+    instruction->begin = begin;
 
-    ir_ref_bb(resume_block);
+    ir_ref_instruction(&begin->base, irb->current_basic_block);
 
     return &instruction->base;
 }
@@ -7890,22 +7886,15 @@ static IrInstruction *ir_gen_suspend(IrBuilder *irb, Scope *parent_scope, AstNod
         return irb->codegen->invalid_instruction;
     }
 
-    IrBasicBlock *resume_block = ir_create_basic_block(irb, parent_scope, "SuspendResume");
-
-    ir_build_suspend_begin(irb, parent_scope, node, resume_block);
+    IrInstructionSuspendBegin *begin = ir_build_suspend_begin(irb, parent_scope, node);
     if (node->data.suspend.block != nullptr) {
-        Scope *child_scope;
         ScopeSuspend *suspend_scope = create_suspend_scope(irb->codegen, node, parent_scope);
-        suspend_scope->resume_block = resume_block;
-        child_scope = &suspend_scope->base;
+        Scope *child_scope = &suspend_scope->base;
         IrInstruction *susp_res = ir_gen_node(irb, node->data.suspend.block, child_scope);
         ir_mark_gen(ir_build_check_statement_is_void(irb, child_scope, node->data.suspend.block, susp_res));
     }
 
-    IrInstruction *result = ir_build_suspend_br(irb, parent_scope, node, resume_block);
-    result->value.type = irb->codegen->builtin_types.entry_void;
-    ir_set_cursor_at_end_and_append_block(irb, resume_block);
-    return result;
+    return ir_build_suspend_finish(irb, parent_scope, node, begin);
 }
 
 static IrInstruction *ir_gen_node_raw(IrBuilder *irb, AstNode *node, Scope *scope,
@@ -24458,35 +24447,28 @@ static IrInstruction *ir_analyze_instruction_union_init_named_field(IrAnalyze *i
 }
 
 static IrInstruction *ir_analyze_instruction_suspend_begin(IrAnalyze *ira, IrInstructionSuspendBegin *instruction) {
-    IrBasicBlock *new_bb = ir_get_new_bb_runtime(ira, instruction->resume_block, &instruction->base);
-    if (new_bb == nullptr)
-        return ir_unreach_error(ira);
-    return ir_build_suspend_begin(&ira->new_irb, instruction->base.scope, instruction->base.source_node, new_bb);
+    IrInstructionSuspendBegin *result = ir_build_suspend_begin(&ira->new_irb, instruction->base.scope,
+            instruction->base.source_node);
+    return &result->base;
 }
 
-static IrInstruction *ir_analyze_instruction_suspend_br(IrAnalyze *ira, IrInstructionSuspendBr *instruction) {
-    IrBasicBlock *old_dest_block = instruction->resume_block;
-
-    IrBasicBlock *new_bb = ir_get_new_bb_runtime(ira, old_dest_block, &instruction->base);
-    if (new_bb == nullptr)
-        return ir_unreach_error(ira);
+static IrInstruction *ir_analyze_instruction_suspend_finish(IrAnalyze *ira,
+        IrInstructionSuspendFinish *instruction)
+{
+    IrInstruction *begin_base = instruction->begin->base.child;
+    if (type_is_invalid(begin_base->value.type))
+        return ira->codegen->invalid_instruction;
+    ir_assert(begin_base->id == IrInstructionIdSuspendBegin, &instruction->base);
+    IrInstructionSuspendBegin *begin = reinterpret_cast<IrInstructionSuspendBegin *>(begin_base);
 
     ZigFn *fn_entry = exec_fn_entry(ira->new_irb.exec);
     ir_assert(fn_entry != nullptr, &instruction->base);
 
-    new_bb->resume_index = fn_entry->resume_blocks.length + coro_extra_resume_block_count;
-
-    fn_entry->resume_blocks.append(new_bb);
     if (fn_entry->inferred_async_node == nullptr) {
         fn_entry->inferred_async_node = instruction->base.source_node;
     }
 
-    ir_push_resume_block(ira, old_dest_block);
-
-    IrInstruction *result = ir_build_suspend_br(&ira->new_irb,
-            instruction->base.scope, instruction->base.source_node, new_bb);
-    result->value.type = ira->codegen->builtin_types.entry_unreachable;
-    return ir_finish_anal(ira, result);
+    return ir_build_suspend_finish(&ira->new_irb, instruction->base.scope, instruction->base.source_node, begin);
 }
 
 static IrInstruction *ir_analyze_instruction_await(IrAnalyze *ira, IrInstructionAwait *instruction) {
@@ -24847,8 +24829,8 @@ static IrInstruction *ir_analyze_instruction_base(IrAnalyze *ira, IrInstruction
             return ir_analyze_instruction_union_init_named_field(ira, (IrInstructionUnionInitNamedField *)instruction);
         case IrInstructionIdSuspendBegin:
             return ir_analyze_instruction_suspend_begin(ira, (IrInstructionSuspendBegin *)instruction);
-        case IrInstructionIdSuspendBr:
-            return ir_analyze_instruction_suspend_br(ira, (IrInstructionSuspendBr *)instruction);
+        case IrInstructionIdSuspendFinish:
+            return ir_analyze_instruction_suspend_finish(ira, (IrInstructionSuspendFinish *)instruction);
         case IrInstructionIdCoroResume:
             return ir_analyze_instruction_coro_resume(ira, (IrInstructionCoroResume *)instruction);
         case IrInstructionIdAwait:
@@ -24986,7 +24968,7 @@ bool ir_has_side_effects(IrInstruction *instruction) {
         case IrInstructionIdVectorToArray:
         case IrInstructionIdResetResult:
         case IrInstructionIdSuspendBegin:
-        case IrInstructionIdSuspendBr:
+        case IrInstructionIdSuspendFinish:
         case IrInstructionIdCoroResume:
         case IrInstructionIdAwait:
             return true;
src/ir_print.cpp
@@ -1534,10 +1534,8 @@ static void ir_print_suspend_begin(IrPrint *irp, IrInstructionSuspendBegin *inst
     fprintf(irp->f, "@suspendBegin()");
 }
 
-static void ir_print_suspend_br(IrPrint *irp, IrInstructionSuspendBr *instruction) {
-    fprintf(irp->f, "@suspendBr(");
-    ir_print_other_block(irp, instruction->resume_block);
-    fprintf(irp->f, ")");
+static void ir_print_suspend_finish(IrPrint *irp, IrInstructionSuspendFinish *instruction) {
+    fprintf(irp->f, "@suspendFinish()");
 }
 
 static void ir_print_coro_resume(IrPrint *irp, IrInstructionCoroResume *instruction) {
@@ -2025,8 +2023,8 @@ static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
         case IrInstructionIdSuspendBegin:
             ir_print_suspend_begin(irp, (IrInstructionSuspendBegin *)instruction);
             break;
-        case IrInstructionIdSuspendBr:
-            ir_print_suspend_br(irp, (IrInstructionSuspendBr *)instruction);
+        case IrInstructionIdSuspendFinish:
+            ir_print_suspend_finish(irp, (IrInstructionSuspendFinish *)instruction);
             break;
         case IrInstructionIdCoroResume:
             ir_print_coro_resume(irp, (IrInstructionCoroResume *)instruction);