coroutines: fix llvm error of instruction not dominating uses

See #727

Author: andrewrk

src/ir.cpp

@@ -5983,6 +5983,7 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
     IrInstruction *coro_id;
     IrInstruction *coro_promise_ptr;
     IrInstruction *coro_result_field_ptr;
+    IrInstruction *coro_need_dyn_alloc;
     TypeTableEntry *return_type;
     Buf *result_ptr_field_name;
     if (is_async) {
@@ -6012,13 +6013,13 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
                 get_pointer_to_type(irb->codegen, irb->codegen->builtin_types.entry_u8, false));
         IrInstruction *promise_as_u8_ptr = ir_build_ptr_cast(irb, scope, node, u8_ptr_type, coro_promise_ptr);
         coro_id = ir_build_coro_id(irb, scope, node, promise_as_u8_ptr);
-        IrInstruction *need_dyn_alloc = ir_build_coro_alloc(irb, scope, node, coro_id);
+        coro_need_dyn_alloc = ir_build_coro_alloc(irb, scope, node, coro_id);
         IrInstruction *zero = ir_build_const_usize(irb, scope, node, 0);
         IrInstruction *null_ptr = ir_build_int_to_ptr(irb, scope, node, u8_ptr_type, zero);
 
         IrBasicBlock *dyn_alloc_block = ir_create_basic_block(irb, scope, "DynAlloc");
         IrBasicBlock *coro_begin_block = ir_create_basic_block(irb, scope, "CoroBegin");
-        ir_build_cond_br(irb, scope, node, need_dyn_alloc, dyn_alloc_block, coro_begin_block, const_bool_false);
+        ir_build_cond_br(irb, scope, node, coro_need_dyn_alloc, dyn_alloc_block, coro_begin_block, const_bool_false);
 
         ir_set_cursor_at_end_and_append_block(irb, dyn_alloc_block);
         IrInstruction *coro_size = ir_build_coro_size(irb, scope, node);
@@ -6047,22 +6048,34 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
         ir_build_coro_alloc_fail(irb, scope, node, err_val);
 
         ir_set_cursor_at_end_and_append_block(irb, alloc_ok_block);
-        coro_unwrapped_mem_ptr = ir_build_unwrap_err_payload(irb, scope, node, alloc_result_ptr, false);
+        IrInstruction *unwrapped_mem_ptr = ir_build_unwrap_err_payload(irb, scope, node, alloc_result_ptr, false);
         Buf *ptr_field_name = buf_create_from_str("ptr");
-        IrInstruction *coro_mem_ptr_field = ir_build_field_ptr(irb, scope, node, coro_unwrapped_mem_ptr,
+        IrInstruction *coro_mem_ptr_field = ir_build_field_ptr(irb, scope, node, unwrapped_mem_ptr,
                 ptr_field_name);
         IrInstruction *coro_mem_ptr = ir_build_load_ptr(irb, scope, node, coro_mem_ptr_field);
         ir_build_br(irb, scope, node, coro_begin_block, const_bool_false);
 
         ir_set_cursor_at_end_and_append_block(irb, coro_begin_block);
-        IrBasicBlock **incoming_blocks = allocate<IrBasicBlock *>(2);
-        IrInstruction **incoming_values = allocate<IrInstruction *>(2);
-        incoming_blocks[0] = entry_block;
-        incoming_values[0] = null_ptr;
-        incoming_blocks[1] = alloc_ok_block;
-        incoming_values[1] = coro_mem_ptr;
-        IrInstruction *coro_mem = ir_build_phi(irb, scope, node, 2, incoming_blocks, incoming_values);
+
+        IrBasicBlock **coro_mem_incoming_blocks = allocate<IrBasicBlock *>(2);
+        IrInstruction **coro_mem_incoming_values = allocate<IrInstruction *>(2);
+        coro_mem_incoming_blocks[0] = entry_block;
+        coro_mem_incoming_values[0] = null_ptr;
+        coro_mem_incoming_blocks[1] = alloc_ok_block;
+        coro_mem_incoming_values[1] = coro_mem_ptr;
+        IrInstruction *coro_mem = ir_build_phi(irb, scope, node, 2, coro_mem_incoming_blocks, coro_mem_incoming_values);
+
+        IrBasicBlock **unwrapped_mem_ptr_incoming_blocks = allocate<IrBasicBlock *>(2);
+        IrInstruction **unwrapped_mem_ptr_incoming_values = allocate<IrInstruction *>(2);
+        unwrapped_mem_ptr_incoming_blocks[0] = entry_block;
+        unwrapped_mem_ptr_incoming_values[0] = ir_build_const_undefined(irb, scope, node);
+        unwrapped_mem_ptr_incoming_blocks[1] = alloc_ok_block;
+        unwrapped_mem_ptr_incoming_values[1] = unwrapped_mem_ptr;
+        coro_unwrapped_mem_ptr = ir_build_phi(irb, scope, node, 2,
+                unwrapped_mem_ptr_incoming_blocks, unwrapped_mem_ptr_incoming_values);
+
         irb->exec->coro_handle = ir_build_coro_begin(irb, scope, node, coro_id, coro_mem);
+
         irb->exec->coro_early_final = ir_create_basic_block(irb, scope, "CoroEarlyFinal");
         irb->exec->coro_normal_final = ir_create_basic_block(irb, scope, "CoroNormalFinal");
     }
@@ -6123,11 +6136,9 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
         incoming_blocks[1] = irb->exec->coro_normal_final;
         incoming_values[1] = const_bool_true;
         IrInstruction *resume_awaiter = ir_build_phi(irb, scope, node, 2, incoming_blocks, incoming_values);
-        IrInstruction *mem_to_free = ir_build_coro_free(irb, scope, node, coro_id, irb->exec->coro_handle);
-        IrInstruction *is_non_null = ir_build_test_nonnull(irb, scope, node, mem_to_free);
         IrBasicBlock *dyn_free_block = ir_create_basic_block(irb, scope, "DynFree");
         IrBasicBlock *end_free_block = ir_create_basic_block(irb, scope, "EndFree");
-        ir_build_cond_br(irb, scope, node, is_non_null, dyn_free_block, end_free_block, const_bool_false);
+        ir_build_cond_br(irb, scope, node, coro_need_dyn_alloc, dyn_free_block, end_free_block, const_bool_false);
 
         ir_set_cursor_at_end_and_append_block(irb, dyn_free_block);
         Buf *free_field_name = buf_create_from_str(ASYNC_FREE_FIELD_NAME);