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C ABI: support returning large structs on x86_64

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also panic instead of emitting bad code for returning small structs

See #1481
This commit is contained in:
Andrew Kelley 2018-09-07 20:09:33 -04:00
parent 9017efee22
commit 9c169f3cf7
No known key found for this signature in database
GPG Key ID: 4E7CD66038A4D47C
9 changed files with 193 additions and 129 deletions
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7
src/all_types.hpp
View File

@ -40,6 +40,13 @@ struct Tld;
struct TldExport;
struct IrAnalyze;
enum X64CABIClass {
X64CABIClass_Unknown,
X64CABIClass_MEMORY,
X64CABIClass_INTEGER,
X64CABIClass_SSE,
};
struct IrExecutable {
ZigList<IrBasicBlock *> basic_block_list;
Buf *name;

109
src/analyze.cpp
View File

@ -1009,10 +1009,6 @@ ZigType *get_bound_fn_type(CodeGen *g, ZigFn *fn_entry) {
return bound_fn_type;
}
bool calling_convention_does_first_arg_return(CallingConvention cc) {
return cc == CallingConventionUnspecified;
}
const char *calling_convention_name(CallingConvention cc) {
switch (cc) {
case CallingConventionUnspecified: return "undefined";
@ -1061,6 +1057,26 @@ ZigType *get_ptr_to_stack_trace_type(CodeGen *g) {
return g->ptr_to_stack_trace_type;
}
bool want_first_arg_sret(CodeGen *g, FnTypeId *fn_type_id) {
if (fn_type_id->cc == CallingConventionUnspecified) {
return handle_is_ptr(fn_type_id->return_type);
}
if (fn_type_id->cc != CallingConventionC) {
return false;
}
if (type_is_c_abi_int(g, fn_type_id->return_type)) {
return false;
}
if (g->zig_target.arch.arch == ZigLLVM_x86_64) {
X64CABIClass abi_class = type_c_abi_x86_64_class(g, fn_type_id->return_type);
if (abi_class == X64CABIClass_MEMORY) {
return true;
}
zig_panic("TODO implement C ABI for x86_64 return types. '%s'", buf_ptr(&fn_type_id->return_type->name));
}
zig_panic("TODO implement C ABI for this architecture");
}
ZigType *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
Error err;
auto table_entry = g->fn_type_table.maybe_get(fn_type_id);
@ -1116,8 +1132,7 @@ ZigType *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
// next, loop over the parameters again and compute debug information
// and codegen information
if (!skip_debug_info) {
bool first_arg_return = calling_convention_does_first_arg_return(fn_type_id->cc) &&
handle_is_ptr(fn_type_id->return_type);
bool first_arg_return = want_first_arg_sret(g, fn_type_id);
bool is_async = fn_type_id->cc == CallingConventionAsync;
bool is_c_abi = fn_type_id->cc == CallingConventionC;
bool prefix_arg_error_return_trace = g->have_err_ret_tracing && fn_type_can_fail(fn_type_id);
@ -6367,3 +6382,85 @@ not_integer:
}
return nullptr;
}
X64CABIClass type_c_abi_x86_64_class(CodeGen *g, ZigType *ty) {
size_t ty_size = type_size(g, ty);
if (get_codegen_ptr_type(ty) != nullptr)
return X64CABIClass_INTEGER;
switch (ty->id) {
case ZigTypeIdEnum:
case ZigTypeIdInt:
case ZigTypeIdBool:
return X64CABIClass_INTEGER;
case ZigTypeIdFloat:
return X64CABIClass_SSE;
case ZigTypeIdStruct: {
// "If the size of an object is larger than four eightbytes, or it contains unaligned
// fields, it has class MEMORY"
if (ty_size > 32)
return X64CABIClass_MEMORY;
if (ty->data.structure.layout != ContainerLayoutExtern) {
// TODO determine whether packed structs have any unaligned fields
return X64CABIClass_Unknown;
}
// "If the size of the aggregate exceeds two eightbytes and the first eight-
// byte isn’t SSE or any other eightbyte isn’t SSEUP, the whole argument
// is passed in memory."
if (ty_size > 16) {
// Zig doesn't support vectors and large fp registers yet, so this will always
// be memory.
return X64CABIClass_MEMORY;
}
X64CABIClass working_class = X64CABIClass_Unknown;
for (uint32_t i = 0; i < ty->data.structure.src_field_count; i += 1) {
X64CABIClass field_class = type_c_abi_x86_64_class(g, ty->data.structure.fields->type_entry);
if (field_class == X64CABIClass_Unknown)
return X64CABIClass_Unknown;
if (i == 0 || field_class == X64CABIClass_MEMORY || working_class == X64CABIClass_SSE) {
working_class = field_class;
}
}
return working_class;
}
case ZigTypeIdUnion: {
// "If the size of an object is larger than four eightbytes, or it contains unaligned
// fields, it has class MEMORY"
if (ty_size > 32)
return X64CABIClass_MEMORY;
if (ty->data.unionation.layout != ContainerLayoutExtern)
return X64CABIClass_MEMORY;
// "If the size of the aggregate exceeds two eightbytes and the first eight-
// byte isn’t SSE or any other eightbyte isn’t SSEUP, the whole argument
// is passed in memory."
if (ty_size > 16) {
// Zig doesn't support vectors and large fp registers yet, so this will always
// be memory.
return X64CABIClass_MEMORY;
}
X64CABIClass working_class = X64CABIClass_Unknown;
for (uint32_t i = 0; i < ty->data.unionation.src_field_count; i += 1) {
X64CABIClass field_class = type_c_abi_x86_64_class(g, ty->data.unionation.fields->type_entry);
if (field_class == X64CABIClass_Unknown)
return X64CABIClass_Unknown;
if (i == 0 || field_class == X64CABIClass_MEMORY || working_class == X64CABIClass_SSE) {
working_class = field_class;
}
}
return working_class;
}
default:
return X64CABIClass_Unknown;
}
}
// NOTE this does not depend on x86_64
bool type_is_c_abi_int(CodeGen *g, ZigType *ty) {
return (ty->id == ZigTypeIdInt ||
ty->id == ZigTypeIdFloat ||
ty->id == ZigTypeIdBool ||
ty->id == ZigTypeIdEnum ||
ty->id == ZigTypeIdVoid ||
ty->id == ZigTypeIdUnreachable ||
get_codegen_ptr_type(ty) != nullptr);
}

5
src/analyze.hpp
View File

@ -182,7 +182,6 @@ size_t type_id_index(ZigType *entry);
ZigType *get_generic_fn_type(CodeGen *g, FnTypeId *fn_type_id);
Result<bool> type_is_copyable(CodeGen *g, ZigType *type_entry);
LinkLib *create_link_lib(Buf *name);
bool calling_convention_does_first_arg_return(CallingConvention cc);
LinkLib *add_link_lib(CodeGen *codegen, Buf *lib);
uint32_t get_abi_alignment(CodeGen *g, ZigType *type_entry);
@ -211,6 +210,8 @@ bool calling_convention_allows_zig_types(CallingConvention cc);
const char *calling_convention_name(CallingConvention cc);
void walk_function_params(CodeGen *g, ZigType *fn_type, FnWalk *fn_walk);
X64CABIClass type_c_abi_x86_64_class(CodeGen *g, ZigType *ty);
bool type_is_c_abi_int(CodeGen *g, ZigType *ty);
bool want_first_arg_sret(CodeGen *g, FnTypeId *fn_type_id);
#endif

126
src/codegen.cpp
View File

@ -577,19 +577,25 @@ static LLVMValueRef fn_llvm_value(CodeGen *g, ZigFn *fn_table_entry) {
// use the ABI alignment, which is fine.
}
unsigned init_gen_i = 0;
if (!type_has_bits(return_type)) {
// nothing to do
} else if (type_is_codegen_pointer(return_type)) {
addLLVMAttr(fn_table_entry->llvm_value, 0, "nonnull");
} else if (handle_is_ptr(return_type) && calling_convention_does_first_arg_return(cc)) {
} else if (want_first_arg_sret(g, &fn_type->data.fn.fn_type_id)) {
addLLVMArgAttr(fn_table_entry->llvm_value, 0, "sret");
addLLVMArgAttr(fn_table_entry->llvm_value, 0, "nonnull");
if (cc == CallingConventionC) {
addLLVMArgAttr(fn_table_entry->llvm_value, 0, "noalias");
}
init_gen_i = 1;
}
// set parameter attributes
FnWalk fn_walk = {};
fn_walk.id = FnWalkIdAttrs;
fn_walk.data.attrs.fn = fn_table_entry;
fn_walk.data.attrs.gen_i = init_gen_i;
walk_function_params(g, fn_type, &fn_walk);
uint32_t err_ret_trace_arg_index = get_err_ret_trace_arg_index(g, fn_table_entry);
@ -1905,95 +1911,6 @@ static LLVMValueRef build_alloca(CodeGen *g, ZigType *type_entry, const char *na
return result;
}
enum X64CABIClass {
X64CABIClass_Unknown,
X64CABIClass_MEMORY,
X64CABIClass_INTEGER,
X64CABIClass_SSE,
};
static X64CABIClass type_c_abi_x86_64_class(CodeGen *g, ZigType *ty) {
size_t ty_size = type_size(g, ty);
if (get_codegen_ptr_type(ty) != nullptr)
return X64CABIClass_INTEGER;
switch (ty->id) {
case ZigTypeIdEnum:
case ZigTypeIdInt:
case ZigTypeIdBool:
return X64CABIClass_INTEGER;
case ZigTypeIdFloat:
return X64CABIClass_SSE;
case ZigTypeIdStruct: {
// "If the size of an object is larger than four eightbytes, or it contains unaligned
// fields, it has class MEMORY"
if (ty_size > 32)
return X64CABIClass_MEMORY;
if (ty->data.structure.layout != ContainerLayoutExtern) {
// TODO determine whether packed structs have any unaligned fields
return X64CABIClass_Unknown;
}
// "If the size of the aggregate exceeds two eightbytes and the first eight-
// byte isn’t SSE or any other eightbyte isn’t SSEUP, the whole argument
// is passed in memory."
if (ty_size > 16) {
// Zig doesn't support vectors and large fp registers yet, so this will always
// be memory.
return X64CABIClass_MEMORY;
}
X64CABIClass working_class = X64CABIClass_Unknown;
for (uint32_t i = 0; i < ty->data.structure.src_field_count; i += 1) {
X64CABIClass field_class = type_c_abi_x86_64_class(g, ty->data.structure.fields->type_entry);
if (field_class == X64CABIClass_Unknown)
return X64CABIClass_Unknown;
if (i == 0 || field_class == X64CABIClass_MEMORY || working_class == X64CABIClass_SSE) {
working_class = field_class;
}
}
return working_class;
}
case ZigTypeIdUnion: {
// "If the size of an object is larger than four eightbytes, or it contains unaligned
// fields, it has class MEMORY"
if (ty_size > 32)
return X64CABIClass_MEMORY;
if (ty->data.unionation.layout != ContainerLayoutExtern)
return X64CABIClass_MEMORY;
// "If the size of the aggregate exceeds two eightbytes and the first eight-
// byte isn’t SSE or any other eightbyte isn’t SSEUP, the whole argument
// is passed in memory."
if (ty_size > 16) {
// Zig doesn't support vectors and large fp registers yet, so this will always
// be memory.
return X64CABIClass_MEMORY;
}
X64CABIClass working_class = X64CABIClass_Unknown;
for (uint32_t i = 0; i < ty->data.unionation.src_field_count; i += 1) {
X64CABIClass field_class = type_c_abi_x86_64_class(g, ty->data.unionation.fields->type_entry);
if (field_class == X64CABIClass_Unknown)
return X64CABIClass_Unknown;
if (i == 0 || field_class == X64CABIClass_MEMORY || working_class == X64CABIClass_SSE) {
working_class = field_class;
}
}
return working_class;
}
default:
return X64CABIClass_Unknown;
}
}
// NOTE this does not depend on x86_64
static bool type_is_c_abi_int(CodeGen *g, ZigType *ty) {
size_t ty_size = type_size(g, ty);
if (ty_size > g->pointer_size_bytes)
return false;
return (ty->id == ZigTypeIdInt ||
ty->id == ZigTypeIdFloat ||
ty->id == ZigTypeIdBool ||
ty->id == ZigTypeIdEnum ||
get_codegen_ptr_type(ty) != nullptr);
}
static bool iter_function_params_c_abi(CodeGen *g, ZigType *fn_type, FnWalk *fn_walk, size_t src_i) {
// Initialized from the type for some walks, but because of C var args,
// initialized based on callsite instructions for that one.
@ -2327,15 +2244,13 @@ static LLVMValueRef ir_render_return(CodeGen *g, IrExecutable *executable, IrIns
LLVMValueRef value = ir_llvm_value(g, return_instruction->value);
ZigType *return_type = return_instruction->value->value.type;
if (handle_is_ptr(return_type)) {
if (calling_convention_does_first_arg_return(g->cur_fn->type_entry->data.fn.fn_type_id.cc)) {
assert(g->cur_ret_ptr);
gen_assign_raw(g, g->cur_ret_ptr, get_pointer_to_type(g, return_type, false), value);
LLVMBuildRetVoid(g->builder);
} else {
LLVMValueRef by_val_value = gen_load_untyped(g, value, 0, false, "");
LLVMBuildRet(g->builder, by_val_value);
}
if (want_first_arg_sret(g, &g->cur_fn->type_entry->data.fn.fn_type_id)) {
assert(g->cur_ret_ptr);
gen_assign_raw(g, g->cur_ret_ptr, get_pointer_to_type(g, return_type, false), value);
LLVMBuildRetVoid(g->builder);
} else if (handle_is_ptr(return_type)) {
LLVMValueRef by_val_value = gen_load_untyped(g, value, 0, false, "");
LLVMBuildRet(g->builder, by_val_value);
} else {
LLVMBuildRet(g->builder, value);
}
@ -3551,8 +3466,7 @@ static LLVMValueRef ir_render_call(CodeGen *g, IrExecutable *executable, IrInstr
CallingConvention cc = fn_type->data.fn.fn_type_id.cc;
bool first_arg_ret = ret_has_bits && handle_is_ptr(src_return_type) &&
calling_convention_does_first_arg_return(cc);
bool first_arg_ret = ret_has_bits && want_first_arg_sret(g, fn_type_id);
bool prefix_arg_err_ret_stack = get_prefix_arg_err_ret_stack(g, fn_type_id);
bool is_var_args = fn_type_id->is_var_args;
ZigList<LLVMValueRef> gen_param_values = {};
@ -6260,13 +6174,14 @@ static void do_code_gen(CodeGen *g) {
// Generate function definitions.
for (size_t fn_i = 0; fn_i < g->fn_defs.length; fn_i += 1) {
ZigFn *fn_table_entry = g->fn_defs.at(fn_i);
CallingConvention cc = fn_table_entry->type_entry->data.fn.fn_type_id.cc;
FnTypeId *fn_type_id = &fn_table_entry->type_entry->data.fn.fn_type_id;
CallingConvention cc = fn_type_id->cc;
bool is_c_abi = cc == CallingConventionC;
LLVMValueRef fn = fn_llvm_value(g, fn_table_entry);
g->cur_fn = fn_table_entry;
g->cur_fn_val = fn;
ZigType *return_type = fn_table_entry->type_entry->data.fn.fn_type_id.return_type;
ZigType *return_type = fn_type_id->return_type;
if (handle_is_ptr(return_type)) {
g->cur_ret_ptr = LLVMGetParam(fn, 0);
} else {
@ -6344,13 +6259,15 @@ static void do_code_gen(CodeGen *g) {
ImportTableEntry *import = get_scope_import(&fn_table_entry->fndef_scope->base);
unsigned gen_i_init = want_first_arg_sret(g, fn_type_id) ? 1 : 0;
// create debug variable declarations for variables and allocate all local variables
FnWalk fn_walk_var = {};
fn_walk_var.id = FnWalkIdVars;
fn_walk_var.data.vars.import = import;
fn_walk_var.data.vars.fn = fn_table_entry;
fn_walk_var.data.vars.llvm_fn = fn;
fn_walk_var.data.vars.gen_i = 0;
fn_walk_var.data.vars.gen_i = gen_i_init;
for (size_t var_i = 0; var_i < fn_table_entry->variable_list.length; var_i += 1) {
ZigVar *var = fn_table_entry->variable_list.at(var_i);
@ -6429,6 +6346,7 @@ static void do_code_gen(CodeGen *g) {
fn_walk_init.id = FnWalkIdInits;
fn_walk_init.data.inits.fn = fn_table_entry;
fn_walk_init.data.inits.llvm_fn = fn;
fn_walk_init.data.inits.gen_i = gen_i_init;
walk_function_params(g, fn_table_entry->type_entry, &fn_walk_init);
ir_render(g, fn_table_entry);

1
test/behavior.zig
View File

@ -9,7 +9,6 @@ comptime {
_ = @import("cases/bitcast.zig");
_ = @import("cases/bool.zig");
_ = @import("cases/bugs/1111.zig");
_ = @import("cases/bugs/1230.zig");
_ = @import("cases/bugs/1277.zig");
_ = @import("cases/bugs/1421.zig");
_ = @import("cases/bugs/394.zig");

14
test/cases/bugs/1230.zig
View File

@ -1,14 +0,0 @@
const assert = @import("std").debug.assert;
const S = extern struct {
x: i32,
};
extern fn ret_struct() S {
return S{ .x = 42 };
}
test "extern return small struct (bug 1230)" {
const s = ret_struct();
assert(s.x == 42);
}

1
test/stage1/c_abi/build.zig
View File

@ -5,6 +5,7 @@ pub fn build(b: *Builder) void {
const c_obj = b.addCObject("cfuncs", "cfuncs.c");
c_obj.setBuildMode(rel_opts);
c_obj.setNoStdLib(true);
const main = b.addTest("main.zig");
main.setBuildMode(rel_opts);

25
test/stage1/c_abi/cfuncs.c
View File

@ -59,6 +59,8 @@ struct SplitStructInts {
};
void zig_split_struct_ints(struct SplitStructInts);
struct BigStruct zig_big_struct_both(struct BigStruct);
void run_c_tests(void) {
zig_u8(0xff);
zig_u16(0xfffe);
@ -77,8 +79,7 @@ void run_c_tests(void) {
zig_bool(true);
// TODO making this non-static crashes for some reason
static uint8_t array[10] = {'1', '2', '3', '4', '5', '6', '7', '8', '9', '0'};
uint8_t array[10] = {'1', '2', '3', '4', '5', '6', '7', '8', '9', '0'};
zig_array(array);
{
@ -95,6 +96,16 @@ void run_c_tests(void) {
struct SplitStructInts s = {1234, 100, 1337};
zig_split_struct_ints(s);
}
{
struct BigStruct s = {30, 31, 32, 33, 34};
struct BigStruct res = zig_big_struct_both(s);
assert_or_panic(res.a == 20);
assert_or_panic(res.b == 21);
assert_or_panic(res.c == 22);
assert_or_panic(res.d == 23);
assert_or_panic(res.e == 24);
}
}
void c_u8(uint8_t x) {
@ -185,3 +196,13 @@ void c_split_struct_ints(struct SplitStructInts x) {
assert_or_panic(x.b == 100);
assert_or_panic(x.c == 1337);
}
struct BigStruct c_big_struct_both(struct BigStruct x) {
assert_or_panic(x.a == 1);
assert_or_panic(x.b == 2);
assert_or_panic(x.c == 3);
assert_or_panic(x.d == 4);
assert_or_panic(x.e == 5);
struct BigStruct y = {10, 11, 12, 13, 14};
return y;
}

34
test/stage1/c_abi/main.zig
View File

@ -203,3 +203,37 @@ export fn zig_split_struct_ints(x: SplitStructInt) void {
assertOrPanic(x.b == 100);
assertOrPanic(x.c == 1337);
}
extern fn c_big_struct_both(BigStruct) BigStruct;
test "C ABI sret and byval together" {
var s = BigStruct{
.a = 1,
.b = 2,
.c = 3,
.d = 4,
.e = 5,
};
var y = c_big_struct_both(s);
assertOrPanic(y.a == 10);
assertOrPanic(y.b == 11);
assertOrPanic(y.c == 12);
assertOrPanic(y.d == 13);
assertOrPanic(y.e == 14);
}
export fn zig_big_struct_both(x: BigStruct) BigStruct {
assertOrPanic(x.a == 30);
assertOrPanic(x.b == 31);
assertOrPanic(x.c == 32);
assertOrPanic(x.d == 33);
assertOrPanic(x.e == 34);
var s = BigStruct{
.a = 20,
.b = 21,
.c = 22,
.d = 23,
.e = 24,
};
return s;
}