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codegen.c
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#include "widcc.h"
#define GP_MAX 6
#define FP_MAX 8
static FILE *output_file;
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 int va_gp_start;
static int va_fp_start;
static int va_st_start;
static int vla_base_ofs;
static int rtn_ptr_ofs;
static int lvar_stk_sz;
static int peak_stk_usage;
bool dont_reuse_stack;
struct {
int *data;
int depth;
int capacity;
} static tmp_stk;
static void gen_expr(Node *node);
static void gen_stmt(Node *node);
FMTCHK(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 int push_tmpstack(int sz) {
if (tmp_stk.depth == tmp_stk.capacity) {
tmp_stk.capacity += 4;
tmp_stk.data = realloc(tmp_stk.data, sizeof(int) * tmp_stk.capacity);
}
int offset;
if (dont_reuse_stack) {
peak_stk_usage += 8 * sz;
offset = peak_stk_usage;
} else {
int stk_pos;
if (tmp_stk.depth > 0)
stk_pos = tmp_stk.data[tmp_stk.depth - 1];
else
stk_pos = lvar_stk_sz;
stk_pos += 8 * sz;
peak_stk_usage = MAX(peak_stk_usage, stk_pos);
offset = stk_pos;
}
tmp_stk.data[tmp_stk.depth] = offset;
tmp_stk.depth++;
return offset;
}
static int pop_tmpstack(void) {
tmp_stk.depth--;
return tmp_stk.data[tmp_stk.depth];
}
static int push(void) {
int offset = push_tmpstack(1);
println(" mov %%rax, -%d(%%rbp)", offset);
return offset;
}
static void pop(char *arg) {
int offset = pop_tmpstack();
println(" mov -%d(%%rbp), %s", offset, arg);
}
static void pushf(void) {
int offset = push_tmpstack(1);
println(" movsd %%xmm0, -%d(%%rbp)", offset);
}
static void popf(void) {
int offset = pop_tmpstack();
println(" movsd -%d(%%rbp), %%xmm1", offset);
}
static void push_x87(void) {
int offset = push_tmpstack(2);
println(" fstpt -%d(%%rbp)", offset);
}
static void pop_x87(void) {
int offset = pop_tmpstack();
println(" fldt -%d(%%rbp)", offset);
}
// 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.
static void load_extend_int(Type *ty, int ofs, char *ptr, char *reg) {
char *insn = ty->is_unsigned ? "movz" : "movs";
switch (ty->size) {
case 1: println(" %sbl %d(%s), %s", insn, ofs, ptr, reg); return;
case 2: println(" %swl %d(%s), %s", insn, ofs, ptr, reg); return;
case 4: println(" movl %d(%s), %s", ofs, ptr, reg); return;
case 8: println(" mov %d(%s), %s", ofs, ptr, reg); return;
}
internal_error();
}
// 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;
}
static char *reg_dx(int sz) {
switch (sz) {
case 1: return "%dl";
case 2: return "%dx";
case 4: return "%edx";
case 8: return "%rdx";
}
internal_error();
}
static char *reg_ax(int sz) {
switch (sz) {
case 1: return "%al";
case 2: return "%ax";
case 4: return "%eax";
case 8: return "%rax";
}
internal_error();
}
static char *regop_ax(Type *ty) {
switch (ty->size) {
case 1:
case 2:
case 4: return "%eax";
case 8: return "%rax";
}
internal_error();
}
static void gen_mem_copy(int sofs, char *sptr, int dofs, char *dptr, int sz) {
for (int i = 0; i < sz;) {
int rem = sz - i;
if (rem >= 16) {
println(" movups %d(%s), %%xmm0", i + sofs, sptr);
println(" movups %%xmm0, %d(%s)", i + dofs, dptr);
i += 16;
continue;
}
int p2 = (rem >= 8) ? 8 : (rem >= 4) ? 4 : (rem >= 2) ? 2 : 1;
println(" mov %d(%s), %s", i + sofs, sptr, reg_dx(p2));
println(" mov %s, %d(%s)", reg_dx(p2), i + dofs, dptr);
i += p2;
}
}
static void gen_mem_zero(int dofs, char *dptr, int sz) {
println(" xor %%eax, %%eax");
for (int i = 0; i < sz;) {
int rem = sz - i;
int p2 = (rem >= 8) ? 8 : (rem >= 4) ? 4 : (rem >= 2) ? 2 : 1;
println(" mov %s, %d(%s)", reg_ax(p2), i + dofs, dptr);
i += p2;
}
}
// 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->ofs);
return;
}
// Local variable
if (node->var->is_local) {
println(" lea %d(%%rbp), %%rax", node->var->ofs);
return;
}
if (opt_fpic) {
// Thread-local variable
if (node->var->is_tls) {
println(" data16 lea \"%s\"@tlsgd(%%rip), %%rdi", node->var->name);
println(" .value 0x6666");
println(" rex64");
println(" call __tls_get_addr@PLT");
return;
}
// Function or global variable
println(" mov \"%s\"@GOTPCREL(%%rip), %%rax", node->var->name);
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_CHAIN:
case ND_COMMA:
gen_expr(node->lhs);
gen_addr(node->rhs);
return;
case ND_MEMBER:
switch(node->lhs->kind) {
case ND_FUNCALL:
if (!node->lhs->ret_buffer)
break;
case ND_ASSIGN:
case ND_COND:
case ND_STMT_EXPR:
case ND_VA_ARG:
if (node->lhs->ty->kind != TY_STRUCT && node->lhs->ty->kind != TY_UNION)
break;
gen_expr(node->lhs);
println(" add $%d, %%rax", node->member->offset);
return;
default:
gen_addr(node->lhs);
println(" add $%d, %%rax", node->member->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(" fninit; fldt (%%rax)");
return;
}
load_extend_int(ty, 0, "%rax", regop_ax(ty));
}
// Store %rax to an address that the stack top is pointing to.
static void store(Type *ty) {
pop("%rcx");
switch (ty->kind) {
case TY_STRUCT:
case TY_UNION:
gen_mem_copy(0, "%rax", 0, "%rcx", ty->size);
return;
case TY_FLOAT:
println(" movss %%xmm0, (%%rcx)");
return;
case TY_DOUBLE:
println(" movsd %%xmm0, (%%rcx)");
return;
case TY_LDOUBLE:
println(" fstpt (%%rcx)");
println(" fninit; fldt (%%rcx)");
return;
}
switch (ty->size) {
case 1: println(" mov %%al, (%%rcx)"); return;
case 2: println(" mov %%ax, (%%rcx)"); return;
case 4: println(" mov %%eax, (%%rcx)"); return;
case 8: println(" mov %%rax, (%%rcx)"); return;
}
internal_error();
}
enum { I8, I16, I32, I64, U8, U16, U32, U64, F32, F64, F80 };
static int getTypeId(Type *ty) {
switch (ty->kind) {
case TY_PCHAR:
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:
case TY_LONGLONG:
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[] = "movslq %eax, %rax";
static char i32f64[] = "cvtsi2sdl %eax, %xmm0";
static char i32f80[] = "push %rax; fildl (%rsp); pop %rax";
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; push %rax; fildll (%rsp); pop %rax";
static char i64f32[] = "cvtsi2ssq %rax, %xmm0";
static char i64f64[] = "cvtsi2sdq %rax, %xmm0";
static char i64f80[] = "push %rax; fildll (%rsp); pop %rax";
static char u64f32[] =
"test %rax,%rax; js 1f; pxor %xmm0,%xmm0; cvtsi2ss %rax,%xmm0; jmp 2f; "
"1: mov %rax,%rdx; and $1,%eax; pxor %xmm0,%xmm0; shr %rdx; "
"or %rax,%rdx; cvtsi2ss %rdx,%xmm0; addss %xmm0,%xmm0; 2:";
static char u64f64[] =
"test %rax,%rax; js 1f; pxor %xmm0,%xmm0; cvtsi2sd %rax,%xmm0; jmp 2f; "
"1: mov %rax,%rdx; and $1,%eax; pxor %xmm0,%xmm0; shr %rdx; "
"or %rax,%rdx; cvtsi2sd %rdx,%xmm0; addsd %xmm0,%xmm0; 2:";
static char u64f80[] =
"push %rax; fildq (%rsp); test %rax, %rax; jns 1f;"
"mov $1602224128, %eax; mov %eax, 4(%rsp); fadds 4(%rsp); 1:; pop %rax";
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, %rcx; movq %rcx, %rdx; movl $0x5F000000, %eax; "
"movd %eax, %xmm1; subss %xmm1, %xmm0; cvttss2siq %xmm0, %rax; "
"sarq $63, %rdx; andq %rdx, %rax; orq %rcx, %rax;";
static char f32f64[] = "cvtss2sd %xmm0, %xmm0";
static char f32f80[] = "sub $8, %rsp; movss %xmm0, (%rsp); flds (%rsp); add $8, %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, %rcx; movq %rcx, %rdx; mov $0x43e0000000000000, %rax; "
"movq %rax, %xmm1; subsd %xmm1, %xmm0; cvttsd2siq %xmm0, %rax; "
"sarq $63, %rdx; andq %rdx, %rax; orq %rcx, %rax";
static char f64f32[] = "cvtsd2ss %xmm0, %xmm0";
static char f64f80[] = "sub $8, %rsp; movsd %xmm0, (%rsp); fldl (%rsp); add $8, %rsp";
#define FROM_F80_1 \
"sub $24, %rsp; fnstcw 14(%rsp); movzwl 14(%rsp), %eax; or $12, %ah; " \
"mov %ax, 12(%rsp); fldcw 12(%rsp); "
#define FROM_F80_2 " (%rsp); fldcw 14(%rsp); "
#define FROM_F80_3 "; add $24, %rsp"
static char f80i8[] = FROM_F80_1 "fistps" FROM_F80_2 "movsbl (%rsp), %eax" FROM_F80_3;
static char f80u8[] = FROM_F80_1 "fistps" FROM_F80_2 "movzbl (%rsp), %eax" FROM_F80_3;
static char f80i16[] = FROM_F80_1 "fistps" FROM_F80_2 "movzbl (%rsp), %eax" FROM_F80_3;
static char f80u16[] = FROM_F80_1 "fistpl" FROM_F80_2 "movswl (%rsp), %eax" FROM_F80_3;
static char f80i32[] = FROM_F80_1 "fistpl" FROM_F80_2 "mov (%rsp), %eax" FROM_F80_3;
static char f80u32[] = FROM_F80_1 "fistpl" FROM_F80_2 "mov (%rsp), %eax" FROM_F80_3;
static char f80i64[] = FROM_F80_1 "fistpq" FROM_F80_2 "mov (%rsp), %rax" FROM_F80_3;
static char f80u64[] =
"sub $16, %rsp; movl $0x5f000000, 12(%rsp); flds 12(%rsp); fucomi %st(1), %st; setbe %al;"
"fldz; fcmovbe %st(1), %st; fstp %st(1); fsubrp %st, %st(1); fnstcw 4(%rsp);"
"movzwl 4(%rsp), %ecx; orl $3072, %ecx; movw %cx, 6(%rsp); fldcw 6(%rsp);"
"fistpll 8(%rsp); fldcw 4(%rsp); shlq $63, %rax; xorq 8(%rsp), %rax; add $16, %rsp";
static char f80f32[] = "sub $8, %rsp; fstps (%rsp); movss (%rsp), %xmm0; add $8, %rsp";
static char f80f64[] = "sub $8, %rsp; fstpl (%rsp); movsd (%rsp), %xmm0; add $8, %rsp";
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 gen_cast(Node *node) {
if (node->ty->kind == TY_BOOL) {
Node zero = {.kind = ND_NUM, .ty = node->lhs->ty, .tok = node->tok};
Node expr = {.kind = ND_NE, .lhs = node->lhs, .rhs = &zero, .ty = ty_int, .tok = node->tok};
gen_expr(&expr);
return;
}
gen_expr(node->lhs);
if (node->ty->kind == TY_VOID)
return;
int t1 = getTypeId(node->lhs->ty);
int t2 = getTypeId(node->ty);
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 int calling_convention(Obj *var, int *gp_count, int *fp_count) {
int stack = 0;
int gp = *gp_count, fp = 0;
for (; var; var = var->param_next) {
Type *ty = var->ty;
assert(ty->size != 0);
switch (ty->kind) {
case TY_STRUCT:
case TY_UNION:
if (ty->size <= 16) {
int fp_inc = has_flonum1(ty) + (ty->size > 8 && has_flonum2(ty));
int gp_inc = !has_flonum1(ty) + (ty->size > 8 && !has_flonum2(ty));
if ((!fp_inc || (fp + fp_inc <= FP_MAX)) &&
(!gp_inc || (gp + gp_inc <= GP_MAX))) {
fp += fp_inc;
gp += gp_inc;
continue;
}
}
break;
case TY_FLOAT:
case TY_DOUBLE:
if (fp++ < FP_MAX)
continue;
break;
case TY_LDOUBLE:
break;
default:
if (gp++ < GP_MAX)
continue;
}
var->pass_by_stack = true;
if (ty->align > 8)
stack = align_to(stack, ty->align);
var->stack_offset = stack;
stack += align_to(ty->size, 8);
}
if (gp_count)
*gp_count = MIN(gp, GP_MAX);
if (fp_count)
*fp_count = MIN(fp, FP_MAX);
return stack;
}
// 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 void place_stack_args(Node *node) {
for (Obj *var = node->args; var; var = var->param_next) {
if (!var->pass_by_stack)
continue;
switch (var->ty->kind) {
case TY_STRUCT:
case TY_UNION:
case TY_FLOAT:
case TY_DOUBLE:
case TY_LDOUBLE:
gen_mem_copy(var->ofs, "%rbp",
var->stack_offset, "%rsp",
var->ty->size);
continue;
}
load_extend_int(var->ty, var->ofs, "%rbp", regop_ax(var->ty));
println(" mov %%rax, %d(%%rsp)", var->stack_offset);
}
}
static void place_reg_args(Node *node, bool return_by_stack) {
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 (return_by_stack)
println(" lea %d(%%rbp), %s", node->ret_buffer->ofs, argreg64[gp++]);
for (Obj *var = node->args; var; var = var->param_next) {
if (var->pass_by_stack)
continue;
switch (var->ty->kind) {
case TY_STRUCT:
case TY_UNION:
if (has_flonum1(var->ty))
println(" movsd %d(%%rbp), %%xmm%d", var->ofs, fp++);
else
println(" mov %d(%%rbp), %s", var->ofs, argreg64[gp++]);
if (var->ty->size > 8) {
if (has_flonum2(var->ty))
println(" movsd %d(%%rbp), %%xmm%d", 8 + var->ofs, fp++);
else
println(" mov %d(%%rbp), %s", 8 + var->ofs, argreg64[gp++]);
}
continue;
case TY_FLOAT:
println(" movss %d(%%rbp), %%xmm%d", var->ofs, fp++);
continue;
case TY_DOUBLE:
println(" movsd %d(%%rbp), %%xmm%d", var->ofs, fp++);
continue;
}
char *argreg = var->ty->size <= 4 ? argreg32[gp++] : argreg64[gp++];
load_extend_int(var->ty, var->ofs, "%rbp", argreg);
}
}
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->ofs);
else
println(" movsd %%xmm0, %d(%%rbp)", var->ofs);
fp++;
} else {
for (int i = 0; i < MIN(8, ty->size); i++) {
println(" mov %%al, %d(%%rbp)", var->ofs + 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->ofs + 8);
else
println(" movsd %%xmm%d, %d(%%rbp)", fp, var->ofs + 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->ofs + 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, %%rcx");
if (has_flonum1(ty)) {
assert(ty->size == 4 || 8 <= ty->size);
if (ty->size == 4)
println(" movss (%%rcx), %%xmm0");
else
println(" movsd (%%rcx), %%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(%%rcx), %%al", i);
}
gp++;
}
if (ty->size > 8) {
if (has_flonum2(ty)) {
assert(ty->size == 12 || ty->size == 16);
if (ty->size == 12)
println(" movss 8(%%rcx), %%xmm%d", fp);
else
println(" movsd 8(%%rcx), %%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(%%rcx), %s", i, reg1);
}
}
}
}
static void copy_struct_mem(void) {
Type *ty = current_fn->ty->return_ty;
println(" mov -%d(%%rbp), %%rcx", rtn_ptr_ofs);
gen_mem_copy(0, "%rax", 0, "%rcx", ty->size);
println(" mov %%rcx, %%rax");
}
static void builtin_alloca(Node *node) {
// Shift the temporary area by %rax.
println(" sub %%rax, %%rsp");
// Align frame pointer
println(" and $-16, %%rsp");
if (node->var)
println(" mov %%rsp, %d(%%rbp)", node->var->ofs);
else
println(" mov %%rsp, %%rax");
}
static void dealloc_vla(Node *node) {
if (!current_fn->dealloc_vla || node->top_vla == node->target_vla)
return;
if (node->target_vla)
println(" mov %d(%%rbp), %%rsp", node->target_vla->ofs);
else
println(" mov -%d(%%rbp), %%rsp", vla_base_ofs);
}
static void print_loc(Token *tok) {
static int file_no, line_no;
if (file_no == tok->display_file_no && line_no == tok->display_line_no)
return;
println(" .loc %d %d", tok->display_file_no, tok->display_line_no);
file_no = tok->display_file_no;
line_no = tok->display_line_no;
}
// Generate code for a given node.
static void gen_expr(Node *node) {
if (opt_g)
print_loc(node->tok);
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(" movq $%lu, %%rax", u.u64[0]);
println(" movw $%lu, %%dx", u.u64[1]);
println(" push %%rdx");
println(" push %%rax");
println(" fninit; fldt (%%rsp)");
println(" add $16, %%rsp");
return;
}
}
println(" mov $%ld, %%rax", node->val);
return;
}
case ND_POS:
gen_expr(node->lhs);
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 (is_bitfield(node->lhs)) {
// 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 $%ld, %%rcx", (1L << mem->bit_width) - 1);
println(" and %%rcx, %%rax");
println(" mov %%rax, %%rdx");
pop("%rax");
push();
load(mem->ty);
long mask = ((1L << mem->bit_width) - 1) << mem->bit_offset;
println(" mov $%ld, %%rcx", ~mask);
println(" and %%rcx, %%rax");
println(" mov %%rdx, %%rcx");
println(" shl $%d, %%rcx", mem->bit_offset);
println(" or %%rcx, %%rax");
store(node->ty);
println(" mov %%rdx, %%rax");
if (!mem->ty->is_unsigned) {
println(" shl $%d, %%rax", 64 - mem->bit_width);
println(" sar $%d, %%rax", 64 - mem->bit_width);
}
return;
}
store(node->ty);
return;
case ND_STMT_EXPR:
for (Node *n = node->body; n; n = n->next)
gen_stmt(n);
dealloc_vla(node);
return;
case ND_CHAIN:
case ND_COMMA:
gen_expr(node->lhs);
gen_expr(node->rhs);
return;
case ND_CAST:
gen_cast(node);
return;
case ND_MEMZERO:
gen_mem_zero(node->var->ofs, "%rbp", node->var->ty->size);
return;
case ND_COND: {
int c = count();
gen_expr(node->cond);
println(" test %%al, %%al");
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);
println(" xor $1, %%al");
return;
case ND_BITNOT:
gen_expr(node->lhs);
println(" not %%rax");
return;
case ND_LOGAND: {
int c = count();
gen_expr(node->lhs);
println(" test %%al, %%al");
println(" je .L.false.%d", c);
gen_expr(node->rhs);
println(".L.false.%d:", c);
return;
}
case ND_LOGOR: {
int c = count();
gen_expr(node->lhs);
println(" test %%al, %%al");
println(" jne .L.true.%d", c);
gen_expr(node->rhs);
println(".L.true.%d:", c);
return;
}
case ND_FUNCALL: {
if (node->lhs->kind == ND_VAR && !strcmp(node->lhs->var->name, "alloca")) {
gen_expr(node->args->arg_expr);
builtin_alloca(node);
return;
}
// Evaluate function pointer
gen_expr(node->lhs);
push();
// Evaluate arguments
for (Obj *var = node->args; var; var = var->param_next) {
if (var->arg_expr) {
Node var_node = {.kind = ND_VAR, .var = var, .tok = node->tok};
Node assign_node = {.kind = ND_ASSIGN, .lhs = &var_node, .rhs = var->arg_expr, .tok = node->tok};
add_type(&assign_node);
gen_expr(&assign_node);
}
}
pop("%r10");
// If the return type is a large struct/union, the caller passes
// a pointer to a buffer as if it were the first argument.
bool rtn_by_stk = node->ret_buffer && node->ty->size > 16;
int gp_count = rtn_by_stk;
int fp_count = 0;
int arg_stk_size = calling_convention(node->args, &gp_count, &fp_count);
println(" sub $%d, %%rsp", align_to(arg_stk_size, 16));
place_stack_args(node);
place_reg_args(node, rtn_by_stk);
if (node->lhs->ty->is_variadic)
println(" movl $%d, %%eax", fp_count);
println(" call *%%r10");
println(" add $%d, %%rsp", align_to(arg_stk_size, 16));
// 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.
if (is_integer(node->ty) && node->ty->size < 4) {
if (node->ty->kind == TY_BOOL)
println(" %s", cast_table[getTypeId(ty_int)][getTypeId(ty_uchar)]);