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codegen.c
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#include "chibicc.h"
#define GP_MAX 6
#define FP_MAX 8
static FILE *output_file;
static int depth;
static char *argreg8[] = {"%dil", "%sil", "%dl", "%cl", "%r8b", "%r9b"};
static char *argreg16[] = {"%di", "%si", "%dx", "%cx", "%r8w", "%r9w"};
static char *argreg32[] = {"%edi", "%esi", "%edx", "%ecx", "%r8d", "%r9d"};
static char *argreg64[] = {"%rdi", "%rsi", "%rdx", "%rcx", "%r8", "%r9"};
static Obj *current_fn;
static void gen_expr(Node *node);
static void gen_stmt(Node *node);
__attribute__((format(printf, 1, 2)))
static void println(char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
vfprintf(output_file, fmt, ap);
va_end(ap);
fprintf(output_file, "\n");
}
static int count(void) {
static int i = 1;
return i++;
}
static void push(void) {
println(" push %%rax");
depth++;
}
static void pop(char *arg) {
println(" pop %s", arg);
depth--;
}
static void pushf(void) {
println(" sub $8, %%rsp");
println(" movsd %%xmm0, (%%rsp)");
depth++;
}
static void popf(int reg) {
println(" movsd (%%rsp), %%xmm%d", reg);
println(" add $8, %%rsp");
depth--;
}
// Round up `n` to the nearest multiple of `align`. For instance,
// align_to(5, 8) returns 8 and align_to(11, 8) returns 16.
int align_to(int n, int align) {
return (n + align - 1) / align * align;
}
// Compute the absolute address of a given node.
// It's an error if a given node does not reside in memory.
static void gen_addr(Node *node) {
switch (node->kind) {
case ND_VAR:
// Variable-length array, which is always local.
if (node->var->ty->kind == TY_VLA) {
println(" mov %d(%%rbp), %%rax", node->var->offset);
return;
}
// Local variable
if (node->var->is_local) {
println(" lea %d(%%rbp), %%rax", node->var->offset);
return;
}
// Thread-local variable
if (node->var->is_tls) {
println(" mov %%fs:0, %%rax");
println(" add $%s@tpoff, %%rax", node->var->name);
return;
}
// Here, we generate an absolute address of a function or a global
// variable. Even though they exist at a certain address at runtime,
// their addresses are not known at link-time for the following
// two reasons.
//
// - Address randomization: Executables are loaded to memory as a
// whole but it is not known what address they are loaded to.
// Therefore, at link-time, relative address in the same
// exectuable (i.e. the distance between two functions in the
// same executable) is known, but the absolute address is not
// known.
//
// - Dynamic linking: Dynamic shared objects (DSOs) or .so files
// are loaded to memory alongside an executable at runtime and
// linked by the runtime loader in memory. We know nothing
// about addresses of global stuff that may be defined by DSOs
// until the runtime relocation is complete.
//
// In order to deal with the former case, we use RIP-relative
// addressing, denoted by `(%rip)`. For the latter, we obtain an
// address of a stuff that may be in a shared object file from the
// Global Offset Table using `@GOTPCREL(%rip)` notation.
// Function
if (node->ty->kind == TY_FUNC) {
if (node->var->is_definition)
println(" lea %s(%%rip), %%rax", node->var->name);
else
println(" mov %s@GOTPCREL(%%rip), %%rax", node->var->name);
return;
}
// Global variable
println(" lea %s(%%rip), %%rax", node->var->name);
return;
case ND_DEREF:
gen_expr(node->lhs);
return;
case ND_COMMA:
gen_expr(node->lhs);
gen_addr(node->rhs);
return;
case ND_MEMBER:
gen_addr(node->lhs);
println(" add $%d, %%rax", node->member->offset);
return;
case ND_FUNCALL:
if (node->ret_buffer) {
gen_expr(node);
return;
}
break;
case ND_VLA_PTR:
println(" lea %d(%%rbp), %%rax", node->var->offset);
return;
}
error_tok(node->tok, "not an lvalue");
}
// Load a value from where %rax is pointing to.
static void load(Type *ty) {
switch (ty->kind) {
case TY_ARRAY:
case TY_STRUCT:
case TY_UNION:
case TY_FUNC:
case TY_VLA:
// If it is an array, do not attempt to load a value to the
// register because in general we can't load an entire array to a
// register. As a result, the result of an evaluation of an array
// becomes not the array itself but the address of the array.
// This is where "array is automatically converted to a pointer to
// the first element of the array in C" occurs.
return;
case TY_FLOAT:
println(" movss (%%rax), %%xmm0");
return;
case TY_DOUBLE:
println(" movsd (%%rax), %%xmm0");
return;
case TY_LDOUBLE:
println(" fldt (%%rax)");
return;
}
char *insn = ty->is_unsigned ? "movz" : "movs";
// When we load a char or a short value to a register, we always
// extend them to the size of int, so we can assume the lower half of
// a register always contains a valid value. The upper half of a
// register for char, short and int may contain garbage. When we load
// a long value to a register, it simply occupies the entire register.
if (ty->size == 1)
println(" %sbl (%%rax), %%eax", insn);
else if (ty->size == 2)
println(" %swl (%%rax), %%eax", insn);
else if (ty->size == 4)
println(" movsxd (%%rax), %%rax");
else
println(" mov (%%rax), %%rax");
}
// Store %rax to an address that the stack top is pointing to.
static void store(Type *ty) {
pop("%rdi");
switch (ty->kind) {
case TY_STRUCT:
case TY_UNION:
for (int i = 0; i < ty->size; i++) {
println(" mov %d(%%rax), %%r8b", i);
println(" mov %%r8b, %d(%%rdi)", i);
}
return;
case TY_FLOAT:
println(" movss %%xmm0, (%%rdi)");
return;
case TY_DOUBLE:
println(" movsd %%xmm0, (%%rdi)");
return;
case TY_LDOUBLE:
println(" fstpt (%%rdi)");
return;
}
if (ty->size == 1)
println(" mov %%al, (%%rdi)");
else if (ty->size == 2)
println(" mov %%ax, (%%rdi)");
else if (ty->size == 4)
println(" mov %%eax, (%%rdi)");
else
println(" mov %%rax, (%%rdi)");
}
static void cmp_zero(Type *ty) {
switch (ty->kind) {
case TY_FLOAT:
println(" xorps %%xmm1, %%xmm1");
println(" ucomiss %%xmm1, %%xmm0");
return;
case TY_DOUBLE:
println(" xorpd %%xmm1, %%xmm1");
println(" ucomisd %%xmm1, %%xmm0");
return;
case TY_LDOUBLE:
println(" fldz");
println(" fucomip");
println(" fstp %%st(0)");
return;
}
if (is_integer(ty) && ty->size <= 4)
println(" cmp $0, %%eax");
else
println(" cmp $0, %%rax");
}
enum { I8, I16, I32, I64, U8, U16, U32, U64, F32, F64, F80 };
static int getTypeId(Type *ty) {
switch (ty->kind) {
case TY_CHAR:
return ty->is_unsigned ? U8 : I8;
case TY_SHORT:
return ty->is_unsigned ? U16 : I16;
case TY_INT:
return ty->is_unsigned ? U32 : I32;
case TY_LONG:
return ty->is_unsigned ? U64 : I64;
case TY_FLOAT:
return F32;
case TY_DOUBLE:
return F64;
case TY_LDOUBLE:
return F80;
}
return U64;
}
// The table for type casts
static char i32i8[] = "movsbl %al, %eax";
static char i32u8[] = "movzbl %al, %eax";
static char i32i16[] = "movswl %ax, %eax";
static char i32u16[] = "movzwl %ax, %eax";
static char i32f32[] = "cvtsi2ssl %eax, %xmm0";
static char i32i64[] = "movsxd %eax, %rax";
static char i32f64[] = "cvtsi2sdl %eax, %xmm0";
static char i32f80[] = "mov %eax, -4(%rsp); fildl -4(%rsp)";
static char u32f32[] = "mov %eax, %eax; cvtsi2ssq %rax, %xmm0";
static char u32i64[] = "mov %eax, %eax";
static char u32f64[] = "mov %eax, %eax; cvtsi2sdq %rax, %xmm0";
static char u32f80[] = "mov %eax, %eax; mov %rax, -8(%rsp); fildll -8(%rsp)";
static char i64f32[] = "cvtsi2ssq %rax, %xmm0";
static char i64f64[] = "cvtsi2sdq %rax, %xmm0";
static char i64f80[] = "movq %rax, -8(%rsp); fildll -8(%rsp)";
static char u64f32[] = "cvtsi2ssq %rax, %xmm0";
static char u64f64[] =
"test %rax,%rax; js 1f; pxor %xmm0,%xmm0; cvtsi2sd %rax,%xmm0; jmp 2f; "
"1: mov %rax,%rdi; and $1,%eax; pxor %xmm0,%xmm0; shr %rdi; "
"or %rax,%rdi; cvtsi2sd %rdi,%xmm0; addsd %xmm0,%xmm0; 2:";
static char u64f80[] =
"mov %rax, -8(%rsp); fildq -8(%rsp); test %rax, %rax; jns 1f;"
"mov $1602224128, %eax; mov %eax, -4(%rsp); fadds -4(%rsp); 1:";
static char f32i8[] = "cvttss2sil %xmm0, %eax; movsbl %al, %eax";
static char f32u8[] = "cvttss2sil %xmm0, %eax; movzbl %al, %eax";
static char f32i16[] = "cvttss2sil %xmm0, %eax; movswl %ax, %eax";
static char f32u16[] = "cvttss2sil %xmm0, %eax; movzwl %ax, %eax";
static char f32i32[] = "cvttss2sil %xmm0, %eax";
static char f32u32[] = "cvttss2siq %xmm0, %rax";
static char f32i64[] = "cvttss2siq %xmm0, %rax";
static char f32u64[] = "cvttss2siq %xmm0, %rax";
static char f32f64[] = "cvtss2sd %xmm0, %xmm0";
static char f32f80[] = "movss %xmm0, -4(%rsp); flds -4(%rsp)";
static char f64i8[] = "cvttsd2sil %xmm0, %eax; movsbl %al, %eax";
static char f64u8[] = "cvttsd2sil %xmm0, %eax; movzbl %al, %eax";
static char f64i16[] = "cvttsd2sil %xmm0, %eax; movswl %ax, %eax";
static char f64u16[] = "cvttsd2sil %xmm0, %eax; movzwl %ax, %eax";
static char f64i32[] = "cvttsd2sil %xmm0, %eax";
static char f64u32[] = "cvttsd2siq %xmm0, %rax";
static char f64i64[] = "cvttsd2siq %xmm0, %rax";
static char f64u64[] = "cvttsd2siq %xmm0, %rax";
static char f64f32[] = "cvtsd2ss %xmm0, %xmm0";
static char f64f80[] = "movsd %xmm0, -8(%rsp); fldl -8(%rsp)";
#define FROM_F80_1 \
"fnstcw -10(%rsp); movzwl -10(%rsp), %eax; or $12, %ah; " \
"mov %ax, -12(%rsp); fldcw -12(%rsp); "
#define FROM_F80_2 " -24(%rsp); fldcw -10(%rsp); "
static char f80i8[] = FROM_F80_1 "fistps" FROM_F80_2 "movsbl -24(%rsp), %eax";
static char f80u8[] = FROM_F80_1 "fistps" FROM_F80_2 "movzbl -24(%rsp), %eax";
static char f80i16[] = FROM_F80_1 "fistps" FROM_F80_2 "movzbl -24(%rsp), %eax";
static char f80u16[] = FROM_F80_1 "fistpl" FROM_F80_2 "movswl -24(%rsp), %eax";
static char f80i32[] = FROM_F80_1 "fistpl" FROM_F80_2 "mov -24(%rsp), %eax";
static char f80u32[] = FROM_F80_1 "fistpl" FROM_F80_2 "mov -24(%rsp), %eax";
static char f80i64[] = FROM_F80_1 "fistpq" FROM_F80_2 "mov -24(%rsp), %rax";
static char f80u64[] = FROM_F80_1 "fistpq" FROM_F80_2 "mov -24(%rsp), %rax";
static char f80f32[] = "fstps -8(%rsp); movss -8(%rsp), %xmm0";
static char f80f64[] = "fstpl -8(%rsp); movsd -8(%rsp), %xmm0";
static char *cast_table[][11] = {
// i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 f80
{NULL, NULL, NULL, i32i64, i32u8, i32u16, NULL, i32i64, i32f32, i32f64, i32f80}, // i8
{i32i8, NULL, NULL, i32i64, i32u8, i32u16, NULL, i32i64, i32f32, i32f64, i32f80}, // i16
{i32i8, i32i16, NULL, i32i64, i32u8, i32u16, NULL, i32i64, i32f32, i32f64, i32f80}, // i32
{i32i8, i32i16, NULL, NULL, i32u8, i32u16, NULL, NULL, i64f32, i64f64, i64f80}, // i64
{i32i8, NULL, NULL, i32i64, NULL, NULL, NULL, i32i64, i32f32, i32f64, i32f80}, // u8
{i32i8, i32i16, NULL, i32i64, i32u8, NULL, NULL, i32i64, i32f32, i32f64, i32f80}, // u16
{i32i8, i32i16, NULL, u32i64, i32u8, i32u16, NULL, u32i64, u32f32, u32f64, u32f80}, // u32
{i32i8, i32i16, NULL, NULL, i32u8, i32u16, NULL, NULL, u64f32, u64f64, u64f80}, // u64
{f32i8, f32i16, f32i32, f32i64, f32u8, f32u16, f32u32, f32u64, NULL, f32f64, f32f80}, // f32
{f64i8, f64i16, f64i32, f64i64, f64u8, f64u16, f64u32, f64u64, f64f32, NULL, f64f80}, // f64
{f80i8, f80i16, f80i32, f80i64, f80u8, f80u16, f80u32, f80u64, f80f32, f80f64, NULL}, // f80
};
static void cast(Type *from, Type *to) {
if (to->kind == TY_VOID)
return;
if (to->kind == TY_BOOL) {
cmp_zero(from);
println(" setne %%al");
println(" movzx %%al, %%eax");
return;
}
int t1 = getTypeId(from);
int t2 = getTypeId(to);
if (cast_table[t1][t2])
println(" %s", cast_table[t1][t2]);
}
// Structs or unions equal or smaller than 16 bytes are passed
// using up to two registers.
//
// If the first 8 bytes contains only floating-point type members,
// they are passed in an XMM register. Otherwise, they are passed
// in a general-purpose register.
//
// If a struct/union is larger than 8 bytes, the same rule is
// applied to the the next 8 byte chunk.
//
// This function returns true if `ty` has only floating-point
// members in its byte range [lo, hi).
static bool has_flonum(Type *ty, int lo, int hi, int offset) {
if (ty->kind == TY_STRUCT || ty->kind == TY_UNION) {
for (Member *mem = ty->members; mem; mem = mem->next)
if (!has_flonum(mem->ty, lo, hi, offset + mem->offset))
return false;
return true;
}
if (ty->kind == TY_ARRAY) {
for (int i = 0; i < ty->array_len; i++)
if (!has_flonum(ty->base, lo, hi, offset + ty->base->size * i))
return false;
return true;
}
return offset < lo || hi <= offset || ty->kind == TY_FLOAT || ty->kind == TY_DOUBLE;
}
static bool has_flonum1(Type *ty) {
return has_flonum(ty, 0, 8, 0);
}
static bool has_flonum2(Type *ty) {
return has_flonum(ty, 8, 16, 0);
}
static void push_struct(Type *ty) {
int sz = align_to(ty->size, 8);
println(" sub $%d, %%rsp", sz);
depth += sz / 8;
for (int i = 0; i < ty->size; i++) {
println(" mov %d(%%rax), %%r10b", i);
println(" mov %%r10b, %d(%%rsp)", i);
}
}
static void push_args2(Node *args, bool first_pass) {
if (!args)
return;
push_args2(args->next, first_pass);
if ((first_pass && !args->pass_by_stack) || (!first_pass && args->pass_by_stack))
return;
gen_expr(args);
switch (args->ty->kind) {
case TY_STRUCT:
case TY_UNION:
push_struct(args->ty);
break;
case TY_FLOAT:
case TY_DOUBLE:
pushf();
break;
case TY_LDOUBLE:
println(" sub $16, %%rsp");
println(" fstpt (%%rsp)");
depth += 2;
break;
default:
push();
}
}
// Load function call arguments. Arguments are already evaluated and
// stored to the stack as local variables. What we need to do in this
// function is to load them to registers or push them to the stack as
// specified by the x86-64 psABI. Here is what the spec says:
//
// - Up to 6 arguments of integral type are passed using RDI, RSI,
// RDX, RCX, R8 and R9.
//
// - Up to 8 arguments of floating-point type are passed using XMM0 to
// XMM7.
//
// - If all registers of an appropriate type are already used, push an
// argument to the stack in the right-to-left order.
//
// - Each argument passed on the stack takes 8 bytes, and the end of
// the argument area must be aligned to a 16 byte boundary.
//
// - If a function is variadic, set the number of floating-point type
// arguments to RAX.
static int push_args(Node *node) {
int stack = 0, gp = 0, fp = 0;
// If the return type is a large struct/union, the caller passes
// a pointer to a buffer as if it were the first argument.
if (node->ret_buffer && node->ty->size > 16)
gp++;
// Load as many arguments to the registers as possible.
for (Node *arg = node->args; arg; arg = arg->next) {
Type *ty = arg->ty;
switch (ty->kind) {
case TY_STRUCT:
case TY_UNION:
if (ty->size > 16) {
arg->pass_by_stack = true;
stack += align_to(ty->size, 8) / 8;
} else {
bool fp1 = has_flonum1(ty);
bool fp2 = has_flonum2(ty);
if (fp + fp1 + fp2 < FP_MAX && gp + !fp1 + !fp2 < GP_MAX) {
fp = fp + fp1 + fp2;
gp = gp + !fp1 + !fp2;
} else {
arg->pass_by_stack = true;
stack += align_to(ty->size, 8) / 8;
}
}
break;
case TY_FLOAT:
case TY_DOUBLE:
if (fp++ >= FP_MAX) {
arg->pass_by_stack = true;
stack++;
}
break;
case TY_LDOUBLE:
arg->pass_by_stack = true;
stack += 2;
break;
default:
if (gp++ >= GP_MAX) {
arg->pass_by_stack = true;
stack++;
}
}
}
if ((depth + stack) % 2 == 1) {
println(" sub $8, %%rsp");
depth++;
stack++;
}
push_args2(node->args, true);
push_args2(node->args, false);
// If the return type is a large struct/union, the caller passes
// a pointer to a buffer as if it were the first argument.
if (node->ret_buffer && node->ty->size > 16) {
println(" lea %d(%%rbp), %%rax", node->ret_buffer->offset);
push();
}
return stack;
}
static void copy_ret_buffer(Obj *var) {
Type *ty = var->ty;
int gp = 0, fp = 0;
if (has_flonum1(ty)) {
assert(ty->size == 4 || 8 <= ty->size);
if (ty->size == 4)
println(" movss %%xmm0, %d(%%rbp)", var->offset);
else
println(" movsd %%xmm0, %d(%%rbp)", var->offset);
fp++;
} else {
for (int i = 0; i < MIN(8, ty->size); i++) {
println(" mov %%al, %d(%%rbp)", var->offset + i);
println(" shr $8, %%rax");
}
gp++;
}
if (ty->size > 8) {
if (has_flonum2(ty)) {
assert(ty->size == 12 || ty->size == 16);
if (ty->size == 12)
println(" movss %%xmm%d, %d(%%rbp)", fp, var->offset + 8);
else
println(" movsd %%xmm%d, %d(%%rbp)", fp, var->offset + 8);
} else {
char *reg1 = (gp == 0) ? "%al" : "%dl";
char *reg2 = (gp == 0) ? "%rax" : "%rdx";
for (int i = 8; i < MIN(16, ty->size); i++) {
println(" mov %s, %d(%%rbp)", reg1, var->offset + i);
println(" shr $8, %s", reg2);
}
}
}
}
static void copy_struct_reg(void) {
Type *ty = current_fn->ty->return_ty;
int gp = 0, fp = 0;
println(" mov %%rax, %%rdi");
if (has_flonum(ty, 0, 8, 0)) {
assert(ty->size == 4 || 8 <= ty->size);
if (ty->size == 4)
println(" movss (%%rdi), %%xmm0");
else
println(" movsd (%%rdi), %%xmm0");
fp++;
} else {
println(" mov $0, %%rax");
for (int i = MIN(8, ty->size) - 1; i >= 0; i--) {
println(" shl $8, %%rax");
println(" mov %d(%%rdi), %%al", i);
}
gp++;
}
if (ty->size > 8) {
if (has_flonum(ty, 8, 16, 0)) {
assert(ty->size == 12 || ty->size == 16);
if (ty->size == 4)
println(" movss 8(%%rdi), %%xmm%d", fp);
else
println(" movsd 8(%%rdi), %%xmm%d", fp);
} else {
char *reg1 = (gp == 0) ? "%al" : "%dl";
char *reg2 = (gp == 0) ? "%rax" : "%rdx";
println(" mov $0, %s", reg2);
for (int i = MIN(16, ty->size) - 1; i >= 8; i--) {
println(" shl $8, %s", reg2);
println(" mov %d(%%rdi), %s", i, reg1);
}
}
}
}
static void copy_struct_mem(void) {
Type *ty = current_fn->ty->return_ty;
Obj *var = current_fn->params;
println(" mov %d(%%rbp), %%rdi", var->offset);
for (int i = 0; i < ty->size; i++) {
println(" mov %d(%%rax), %%dl", i);
println(" mov %%dl, %d(%%rdi)", i);
}
}
static void builtin_alloca(void) {
// Align size to 16 bytes.
println(" add $15, %%rdi");
println(" and $0xfffffff0, %%edi");
// Shift the temporary area by %rdi.
println(" mov %d(%%rbp), %%rcx", current_fn->alloca_bottom->offset);
println(" sub %%rsp, %%rcx");
println(" mov %%rsp, %%rax");
println(" sub %%rdi, %%rsp");
println(" mov %%rsp, %%rdx");
println("1:");
println(" cmp $0, %%rcx");
println(" je 2f");
println(" mov (%%rax), %%r8b");
println(" mov %%r8b, (%%rdx)");
println(" inc %%rdx");
println(" inc %%rax");
println(" dec %%rcx");
println(" jmp 1b");
println("2:");
// Move alloca_bottom pointer.
println(" mov %d(%%rbp), %%rax", current_fn->alloca_bottom->offset);
println(" sub %%rdi, %%rax");
println(" mov %%rax, %d(%%rbp)", current_fn->alloca_bottom->offset);
}
// Generate code for a given node.
static void gen_expr(Node *node) {
println(" .loc %d %d", node->tok->file->file_no, node->tok->line_no);
switch (node->kind) {
case ND_NULL_EXPR:
return;
case ND_NUM: {
switch (node->ty->kind) {
case TY_FLOAT: {
union { float f32; uint32_t u32; } u = { node->fval };
println(" mov $%u, %%eax # float %Lf", u.u32, node->fval);
println(" movq %%rax, %%xmm0");
return;
}
case TY_DOUBLE: {
union { double f64; uint64_t u64; } u = { node->fval };
println(" mov $%lu, %%rax # double %Lf", u.u64, node->fval);
println(" movq %%rax, %%xmm0");
return;
}
case TY_LDOUBLE: {
union { long double f80; uint64_t u64[2]; } u;
memset(&u, 0, sizeof(u));
u.f80 = node->fval;
println(" mov $%lu, %%rax # long double %Lf", u.u64[0], node->fval);
println(" mov %%rax, -16(%%rsp)");
println(" mov $%lu, %%rax", u.u64[1]);
println(" mov %%rax, -8(%%rsp)");
println(" fldt -16(%%rsp)");
return;
}
}
println(" mov $%ld, %%rax", node->val);
return;
}
case ND_NEG:
gen_expr(node->lhs);
switch (node->ty->kind) {
case TY_FLOAT:
println(" mov $1, %%rax");
println(" shl $31, %%rax");
println(" movq %%rax, %%xmm1");
println(" xorps %%xmm1, %%xmm0");
return;
case TY_DOUBLE:
println(" mov $1, %%rax");
println(" shl $63, %%rax");
println(" movq %%rax, %%xmm1");
println(" xorpd %%xmm1, %%xmm0");
return;
case TY_LDOUBLE:
println(" fchs");
return;
}
println(" neg %%rax");
return;
case ND_VAR:
gen_addr(node);
load(node->ty);
return;
case ND_MEMBER: {
gen_addr(node);
load(node->ty);
Member *mem = node->member;
if (mem->is_bitfield) {
println(" shl $%d, %%rax", 64 - mem->bit_width - mem->bit_offset);
if (mem->ty->is_unsigned)
println(" shr $%d, %%rax", 64 - mem->bit_width);
else
println(" sar $%d, %%rax", 64 - mem->bit_width);
}
return;
}
case ND_DEREF:
gen_expr(node->lhs);
load(node->ty);
return;
case ND_ADDR:
gen_addr(node->lhs);
return;
case ND_ASSIGN:
gen_addr(node->lhs);
push();
gen_expr(node->rhs);
if (node->lhs->kind == ND_MEMBER && node->lhs->member->is_bitfield) {
println(" mov %%rax, %%r8");
// If the lhs is a bitfield, we need to read the current value
// from memory and merge it with a new value.
Member *mem = node->lhs->member;
println(" mov %%rax, %%rdi");
println(" and $%ld, %%rdi", (1L << mem->bit_width) - 1);
println(" shl $%d, %%rdi", mem->bit_offset);
println(" mov (%%rsp), %%rax");
load(mem->ty);
long mask = ((1L << mem->bit_width) - 1) << mem->bit_offset;
println(" mov $%ld, %%r9", ~mask);
println(" and %%r9, %%rax");
println(" or %%rdi, %%rax");
store(node->ty);
println(" mov %%r8, %%rax");
return;
}
store(node->ty);
return;
case ND_STMT_EXPR:
for (Node *n = node->body; n; n = n->next)
gen_stmt(n);
return;
case ND_COMMA:
gen_expr(node->lhs);
gen_expr(node->rhs);
return;
case ND_CAST:
gen_expr(node->lhs);
cast(node->lhs->ty, node->ty);
return;
case ND_MEMZERO:
// `rep stosb` is equivalent to `memset(%rdi, %al, %rcx)`.
println(" mov $%d, %%rcx", node->var->ty->size);
println(" lea %d(%%rbp), %%rdi", node->var->offset);
println(" mov $0, %%al");
println(" rep stosb");
return;
case ND_COND: {
int c = count();
gen_expr(node->cond);
cmp_zero(node->cond->ty);
println(" je .L.else.%d", c);
gen_expr(node->then);
println(" jmp .L.end.%d", c);
println(".L.else.%d:", c);
gen_expr(node->els);
println(".L.end.%d:", c);
return;
}
case ND_NOT:
gen_expr(node->lhs);
cmp_zero(node->lhs->ty);
println(" sete %%al");
println(" movzx %%al, %%rax");
return;
case ND_BITNOT:
gen_expr(node->lhs);
println(" not %%rax");
return;
case ND_LOGAND: {
int c = count();
gen_expr(node->lhs);
cmp_zero(node->lhs->ty);
println(" je .L.false.%d", c);
gen_expr(node->rhs);
cmp_zero(node->rhs->ty);
println(" je .L.false.%d", c);
println(" mov $1, %%rax");
println(" jmp .L.end.%d", c);
println(".L.false.%d:", c);
println(" mov $0, %%rax");
println(".L.end.%d:", c);
return;
}
case ND_LOGOR: {
int c = count();
gen_expr(node->lhs);
cmp_zero(node->lhs->ty);
println(" jne .L.true.%d", c);
gen_expr(node->rhs);
cmp_zero(node->rhs->ty);
println(" jne .L.true.%d", c);
println(" mov $0, %%rax");
println(" jmp .L.end.%d", c);
println(".L.true.%d:", c);
println(" mov $1, %%rax");
println(".L.end.%d:", c);
return;
}
case ND_FUNCALL: {
if (node->lhs->kind == ND_VAR && !strcmp(node->lhs->var->name, "alloca")) {
gen_expr(node->args);
println(" mov %%rax, %%rdi");
builtin_alloca();
return;
}
int stack_args = push_args(node);
gen_expr(node->lhs);
int gp = 0, fp = 0;
// If the return type is a large struct/union, the caller passes
// a pointer to a buffer as if it were the first argument.
if (node->ret_buffer && node->ty->size > 16)
pop(argreg64[gp++]);
for (Node *arg = node->args; arg; arg = arg->next) {
Type *ty = arg->ty;
switch (ty->kind) {
case TY_STRUCT:
case TY_UNION:
if (ty->size > 16)
continue;
bool fp1 = has_flonum1(ty);
bool fp2 = has_flonum2(ty);
if (fp + fp1 + fp2 < FP_MAX && gp + !fp1 + !fp2 < GP_MAX) {
if (fp1)
popf(fp++);
else
pop(argreg64[gp++]);
if (ty->size > 8) {
if (fp2)
popf(fp++);
else
pop(argreg64[gp++]);
}
}
break;
case TY_FLOAT:
case TY_DOUBLE:
if (fp < FP_MAX)
popf(fp++);
break;
case TY_LDOUBLE:
break;
default:
if (gp < GP_MAX)
pop(argreg64[gp++]);
}
}
println(" mov %%rax, %%r10");
println(" mov $%d, %%rax", fp);
println(" call *%%r10");
println(" add $%d, %%rsp", stack_args * 8);
depth -= stack_args;
// It looks like the most significant 48 or 56 bits in RAX may
// contain garbage if a function return type is short or bool/char,
// respectively. We clear the upper bits here.
switch (node->ty->kind) {
case TY_BOOL:
println(" movzx %%al, %%eax");
return;
case TY_CHAR:
if (node->ty->is_unsigned)
println(" movzbl %%al, %%eax");
else
println(" movsbl %%al, %%eax");
return;
case TY_SHORT:
if (node->ty->is_unsigned)
println(" movzwl %%ax, %%eax");
else
println(" movswl %%ax, %%eax");
return;
}
// If the return type is a small struct, a value is returned
// using up to two registers.
if (node->ret_buffer && node->ty->size <= 16) {
copy_ret_buffer(node->ret_buffer);
println(" lea %d(%%rbp), %%rax", node->ret_buffer->offset);
}
return;
}
}
switch (node->lhs->ty->kind) {
case TY_FLOAT:
case TY_DOUBLE: {
gen_expr(node->rhs);
pushf();
gen_expr(node->lhs);
popf(1);
char *sz = (node->lhs->ty->kind == TY_FLOAT) ? "ss" : "sd";
switch (node->kind) {
case ND_ADD:
println(" add%s %%xmm1, %%xmm0", sz);
return;
case ND_SUB:
println(" sub%s %%xmm1, %%xmm0", sz);
return;
case ND_MUL:
println(" mul%s %%xmm1, %%xmm0", sz);
return;
case ND_DIV:
println(" div%s %%xmm1, %%xmm0", sz);
return;
case ND_EQ:
case ND_NE:
case ND_LT:
case ND_LE:
println(" ucomi%s %%xmm0, %%xmm1", sz);
if (node->kind == ND_EQ) {
println(" sete %%al");
println(" setnp %%dl");
println(" and %%dl, %%al");
} else if (node->kind == ND_NE) {
println(" setne %%al");
println(" setp %%dl");
println(" or %%dl, %%al");
} else if (node->kind == ND_LT) {
println(" seta %%al");
} else {
println(" setae %%al");
}
println(" and $1, %%al");
println(" movzb %%al, %%rax");
return;
}
error_tok(node->tok, "invalid expression");
}
case TY_LDOUBLE: {
gen_expr(node->lhs);
gen_expr(node->rhs);
switch (node->kind) {
case ND_ADD:
println(" faddp");
return;
case ND_SUB:
println(" fsubrp");
return;
case ND_MUL:
println(" fmulp");
return;
case ND_DIV:
println(" fdivrp");
return;
case ND_EQ:
case ND_NE:
case ND_LT:
case ND_LE: