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Merge from upstream Lightening

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This commit is contained in:
Andy Wingo 2019-04-26 12:41:47 +02:00
commit 5b45f04cc8
4 changed files with 610 additions and 617 deletions
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4
libguile/lightening/lightening.h
View file

@ -78,7 +78,6 @@ typedef struct jit_reloc
{
uint8_t kind;
uint8_t inst_start_offset;
uint16_t flags;
uint32_t offset;
} jit_reloc_t;
@ -226,6 +225,9 @@ JIT_API void jit_patch_there(jit_state_t*, jit_reloc_t, jit_pointer_t);
JIT_API void jit_move_operands (jit_state_t *_jit, jit_operand_t *dst,
jit_operand_t *src, size_t argc);
JIT_API size_t jit_align_stack (jit_state_t *_jit, size_t expand);
JIT_API void jit_shrink_stack (jit_state_t *_jit, size_t diff);
/* Note that all functions that take jit_operand_t args[] use the args
as scratch space while shuffling values into position. */
JIT_API void jit_calli(jit_state_t *, jit_pointer_t f,

555
libguile/lightening/lightening/lightening.c
View file

@ -119,15 +119,11 @@ struct jit_state
uint8_t temp_gpr_saved;
uint8_t temp_fpr_saved;
uint8_t overflow;
int frame_size; // Used to know when to align stack.
void* (*alloc)(size_t);
void (*free)(void*);
};
enum jit_reloc_flags
{
JIT_RELOC_CAN_SHORTEN = 1<<0
};
#define ASSERT(x) do { if (!(x)) abort(); } while (0)
#if defined(__GNUC__)
# define UNLIKELY(exprn) __builtin_expect(exprn, 0)
@ -138,7 +134,8 @@ enum jit_reloc_flags
static jit_bool_t jit_get_cpu(void);
static jit_bool_t jit_init(jit_state_t *);
static void jit_flush(void *fptr, void *tptr);
static void jit_try_shorten(jit_state_t *_jit, jit_reloc_t reloc);
static void jit_try_shorten(jit_state_t *_jit, jit_reloc_t reloc,
jit_pointer_t addr);
jit_bool_t
init_jit(void)
@ -189,6 +186,7 @@ jit_begin(jit_state_t *_jit, uint8_t* buf, size_t length)
_jit->pc.uc = _jit->start = buf;
_jit->limit = buf + length;
_jit->overflow = 0;
_jit->frame_size = 0;
}
jit_bool_t
@ -204,6 +202,7 @@ jit_reset(jit_state_t *_jit)
ASSERT (_jit->start);
_jit->pc.uc = _jit->start = _jit->limit = NULL;
_jit->overflow = 0;
_jit->frame_size = 0;
}
void*
@ -225,6 +224,7 @@ jit_end(jit_state_t *_jit, size_t *length)
_jit->pc.uc = _jit->start = _jit->limit = NULL;
_jit->overflow = 0;
_jit->frame_size = 0;
return code;
}
@ -279,13 +279,12 @@ static inline void emit_u64(jit_state_t *_jit, uint64_t u64) {
static inline jit_reloc_t
jit_reloc (jit_state_t *_jit, enum jit_reloc_kind kind,
uint8_t inst_start_offset, uint16_t flags)
uint8_t inst_start_offset)
{
jit_reloc_t ret;
ret.kind = kind;
ret.inst_start_offset = inst_start_offset;
ret.flags = 0;
ret.offset = _jit->pc.uc - _jit->start;
switch (kind)
@ -327,6 +326,7 @@ jit_patch_there(jit_state_t* _jit, jit_reloc_t reloc, jit_pointer_t addr)
if (_jit->overflow)
return;
union jit_pc loc;
uint8_t *end;
loc.uc = _jit->start + reloc.offset;
ptrdiff_t diff;
@ -337,38 +337,37 @@ jit_patch_there(jit_state_t* _jit, jit_reloc_t reloc, jit_pointer_t addr)
*loc.ui = (uintptr_t)addr;
else
*loc.ul = (uintptr_t)addr;
if (loc.uc + sizeof(diff) == _jit->pc.uc &&
(reloc.flags & JIT_RELOC_CAN_SHORTEN))
jit_try_shorten (_jit, reloc);
end = loc.uc + sizeof(diff);
break;
case JIT_RELOC_REL8:
diff = ((uint8_t*)addr) - (loc.uc + 1);
ASSERT (INT8_MIN <= diff && diff <= INT8_MAX);
*loc.uc = diff;
end = loc.uc + 1;
break;
case JIT_RELOC_REL16:
diff = ((uint8_t*)addr) - (loc.uc + 2);
ASSERT (INT16_MIN <= diff && diff <= INT16_MAX);
*loc.us = diff;
if ((loc.uc + 1) == _jit->pc.uc && (reloc.flags & JIT_RELOC_CAN_SHORTEN))
jit_try_shorten (_jit, reloc);
end = loc.uc + 2;
break;
case JIT_RELOC_REL32:
diff = ((uint8_t*)addr) - (loc.uc + 4);
ASSERT (INT32_MIN <= diff && diff <= INT32_MAX);
*loc.ui = diff;
if ((loc.ui + 1) == _jit->pc.ui && (reloc.flags & JIT_RELOC_CAN_SHORTEN))
jit_try_shorten (_jit, reloc);
end = loc.uc + 4;
break;
case JIT_RELOC_REL64:
diff = ((uint8_t*)addr) - (loc.uc + 8);
*loc.ul = diff;
if ((loc.ul + 1) == _jit->pc.ul && (reloc.flags & JIT_RELOC_CAN_SHORTEN))
jit_try_shorten (_jit, reloc);
end = loc.uc + 8;
break;
default:
abort ();
}
if (end == _jit->pc.uc)
jit_try_shorten (_jit, reloc, addr);
}
#if defined(__i386__) || defined(__x86_64__)
@ -467,3 +466,525 @@ jit_patch_there(jit_state_t* _jit, jit_reloc_t reloc, jit_pointer_t addr)
#define IMPL_INSTRUCTION(kind, stem) JIT_IMPL_##kind(stem)
FOR_EACH_INSTRUCTION(IMPL_INSTRUCTION)
#undef IMPL_INSTRUCTION
static void
abi_imm_to_gpr(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t dst,
intptr_t imm)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
ASSERT(0 <= imm);
ASSERT(imm <= UINT8_MAX);
break;
case JIT_OPERAND_ABI_INT8:
ASSERT(INT8_MIN <= imm);
ASSERT(imm <= INT8_MAX);
break;
case JIT_OPERAND_ABI_UINT16:
ASSERT(0 <= imm);
ASSERT(imm <= UINT16_MAX);
break;
case JIT_OPERAND_ABI_INT16:
ASSERT(INT16_MIN <= imm);
ASSERT(imm <= INT16_MAX);
break;
case JIT_OPERAND_ABI_UINT32:
ASSERT(0 <= imm);
ASSERT(imm <= UINT32_MAX);
break;
case JIT_OPERAND_ABI_INT32:
ASSERT(INT32_MIN <= imm);
ASSERT(imm <= INT32_MAX);
break;
#if __WORDSIZE > 32
case JIT_OPERAND_ABI_UINT64:
case JIT_OPERAND_ABI_INT64:
break;
#endif
case JIT_OPERAND_ABI_POINTER:
break;
default:
abort();
}
jit_movi (_jit, dst, imm);
}
static void
abi_gpr_to_mem(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t base, ptrdiff_t offset, jit_gpr_t src)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
case JIT_OPERAND_ABI_INT8:
jit_stxi_c(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_UINT16:
case JIT_OPERAND_ABI_INT16:
jit_stxi_s(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_UINT32:
case JIT_OPERAND_ABI_INT32:
#if __WORDSIZE == 32
case JIT_OPERAND_ABI_POINTER:
#endif
jit_stxi_i(_jit, offset, base, src);
break;
#if __WORDSIZE == 64
case JIT_OPERAND_ABI_UINT64:
case JIT_OPERAND_ABI_INT64:
case JIT_OPERAND_ABI_POINTER:
jit_stxi_l(_jit, offset, base, src);
break;
#endif
default:
abort();
}
}
static void
abi_fpr_to_mem(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t base, ptrdiff_t offset, jit_fpr_t src)
{
switch (abi) {
case JIT_OPERAND_ABI_FLOAT:
jit_stxi_f(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_DOUBLE:
jit_stxi_d(_jit, offset, base, src);
break;
default:
abort();
}
}
static void
abi_mem_to_gpr(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t dst, jit_gpr_t base, ptrdiff_t offset)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
jit_ldxi_uc(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT8:
jit_ldxi_c(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT16:
jit_ldxi_us(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT16:
jit_ldxi_s(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT32:
jit_ldxi_ui(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT32:
jit_ldxi_i(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT64:
jit_ldxi_l(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT64:
jit_ldxi_l(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_POINTER:
jit_ldxi_l(_jit, dst, base, offset);
break;
default:
abort();
}
}
static void
abi_mem_to_fpr(jit_state_t *_jit, enum jit_operand_abi abi,
jit_fpr_t dst, jit_gpr_t base, ptrdiff_t offset)
{
switch (abi) {
case JIT_OPERAND_ABI_FLOAT:
jit_ldxi_f(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_DOUBLE:
jit_ldxi_d(_jit, dst, base, offset);
break;
default:
abort();
}
}
static void
abi_imm_to_mem(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t base,
ptrdiff_t offset, intmax_t imm)
{
ASSERT(!is_fpr_arg(abi));
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_imm_to_gpr(_jit, abi, tmp, imm);
abi_gpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_gpr(_jit);
}
static void
abi_mem_to_mem(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t base,
ptrdiff_t offset, jit_gpr_t src_base, ptrdiff_t src_offset)
{
if (is_gpr_arg (abi)) {
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_mem_to_gpr(_jit, abi, tmp, src_base, src_offset);
abi_gpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_gpr(_jit);
} else {
jit_fpr_t tmp = get_temp_xpr(_jit);
abi_mem_to_fpr(_jit, abi, tmp, src_base, src_offset);
abi_fpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_xpr(_jit);
}
}
#define MOVE_KIND(a, b) ((((int) a) << 4) | ((int) b))
#define MOVE_KIND_ENUM(a, b) \
MOVE_##a##_TO_##b = MOVE_KIND(JIT_OPERAND_KIND_##a, JIT_OPERAND_KIND_##b)
enum move_kind {
MOVE_KIND_ENUM(IMM, GPR),
MOVE_KIND_ENUM(GPR, GPR),
MOVE_KIND_ENUM(MEM, GPR),
MOVE_KIND_ENUM(FPR, FPR),
MOVE_KIND_ENUM(MEM, FPR),
MOVE_KIND_ENUM(IMM, MEM),
MOVE_KIND_ENUM(GPR, MEM),
MOVE_KIND_ENUM(FPR, MEM),
MOVE_KIND_ENUM(MEM, MEM)
};
#undef MOVE_KIND_ENUM
static void
move_operand(jit_state_t *_jit, jit_operand_t dst, jit_operand_t src)
{
switch (MOVE_KIND (src.kind, dst.kind)) {
case MOVE_IMM_TO_GPR:
return abi_imm_to_gpr(_jit, src.abi, dst.loc.gpr.gpr, src.loc.imm);
case MOVE_GPR_TO_GPR:
return jit_movr(_jit, dst.loc.gpr.gpr, src.loc.gpr.gpr);
case MOVE_MEM_TO_GPR:
return abi_mem_to_gpr(_jit, src.abi, dst.loc.gpr.gpr, src.loc.mem.base,
src.loc.mem.offset);
case MOVE_FPR_TO_FPR:
return jit_movr_d(_jit, dst.loc.fpr, src.loc.fpr);
case MOVE_MEM_TO_FPR:
return abi_mem_to_fpr(_jit, src.abi, dst.loc.fpr, src.loc.mem.base,
src.loc.mem.offset);
case MOVE_IMM_TO_MEM:
return abi_imm_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.imm);
case MOVE_GPR_TO_MEM:
return abi_gpr_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.gpr.gpr);
case MOVE_FPR_TO_MEM:
return abi_fpr_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.fpr);
case MOVE_MEM_TO_MEM:
return abi_mem_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.mem.base, src.loc.mem.offset);
default:
abort();
}
}
// A direct transliteration of "Tilting at windmills with Coq: formal
// verification of a compilation algorithm for parallel moves" by
// Laurence Rideau, Bernard Paul Serpette, and Xavier Leroy:
// https://xavierleroy.org/publi/parallel-move.pdf
enum move_status { TO_MOVE, BEING_MOVED, MOVED };
static inline int
already_in_place(jit_operand_t src, jit_operand_t dst)
{
switch (MOVE_KIND(src.kind, dst.kind)) {
case MOVE_GPR_TO_GPR:
return jit_same_gprs (src.loc.gpr.gpr, dst.loc.gpr.gpr);
case MOVE_FPR_TO_FPR:
return jit_same_fprs (src.loc.fpr, dst.loc.fpr);
case MOVE_MEM_TO_MEM:
return jit_same_gprs (src.loc.mem.base, dst.loc.mem.base) &&
src.loc.mem.offset == dst.loc.mem.offset;
default:
return 0;
}
}
static inline int
write_would_clobber(jit_operand_t src, jit_operand_t dst)
{
if (already_in_place (src, dst))
return 1;
if (MOVE_KIND(src.kind, dst.kind) == MOVE_MEM_TO_GPR)
return jit_same_gprs(src.loc.mem.base, dst.loc.gpr.gpr);
return 0;
}
static inline ptrdiff_t
operand_addend(jit_operand_t op)
{
switch (op.kind) {
case JIT_OPERAND_KIND_GPR:
return op.loc.gpr.addend;
case JIT_OPERAND_KIND_MEM:
return op.loc.mem.addend;
default:
abort();
}
}
static void
move_one(jit_state_t *_jit, jit_operand_t *dst, jit_operand_t *src,
size_t argc, enum move_status *status, size_t i)
{
int tmp_gpr = 0, tmp_fpr = 0;
if (already_in_place(src[i], dst[i]))
return;
status[i] = BEING_MOVED;
for (size_t j = 0; j < argc; j++) {
if (write_would_clobber(src[j], dst[i])) {
switch (status[j]) {
case TO_MOVE:
move_one(_jit, dst, src, argc, status, j);
break;
case BEING_MOVED: {
jit_operand_t tmp;
if (is_fpr_arg (src[j].kind)) {
tmp_fpr = 1;
tmp = jit_operand_fpr(src[j].abi, get_temp_xpr(_jit));
} else {
tmp_gpr = 1;
/* Preserve addend, if any, from source operand, to be applied
at the end. */
tmp = jit_operand_gpr_with_addend(src[j].abi, get_temp_gpr(_jit),
operand_addend(src[j]));
}
move_operand (_jit, tmp, src[j]);
src[j] = tmp;
break;
}
case MOVED:
break;
default:
abort ();
}
}
}
move_operand (_jit, dst[i], src[i]);
status[i] = MOVED;
if (tmp_gpr)
unget_temp_gpr(_jit);
else if (tmp_fpr)
unget_temp_xpr(_jit);
}
static void
apply_addend(jit_state_t *_jit, jit_operand_t dst, jit_operand_t src)
{
switch (MOVE_KIND(src.kind, dst.kind)) {
case MOVE_GPR_TO_GPR:
case MOVE_MEM_TO_GPR:
if (operand_addend(src))
jit_addi(_jit, dst.loc.gpr.gpr, dst.loc.gpr.gpr, operand_addend(src));
break;
case MOVE_GPR_TO_MEM:
case MOVE_MEM_TO_MEM:
if (operand_addend(src)) {
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_mem_to_gpr(_jit, dst.abi, tmp, dst.loc.mem.base, dst.loc.mem.offset);
jit_addi(_jit, tmp, tmp, operand_addend(src));
abi_gpr_to_mem(_jit, dst.abi, dst.loc.mem.base, dst.loc.mem.offset, tmp);
}
break;
default:
break;
}
}
/* Preconditions: No dest operand is IMM. No dest operand aliases
another dest operand. No dest MEM operand uses a base register which
is used as a dest GPR. No dst operand has an addend. The registers
returned by get_temp_gpr and get_temp_fpr do not appear in source or
dest args. */
void
jit_move_operands(jit_state_t *_jit, jit_operand_t *dst, jit_operand_t *src,
size_t argc)
{
// Check preconditions, except the condition about tmp registers.
{
uint64_t src_gprs = 0;
uint64_t dst_gprs = 0;
uint64_t dst_fprs = 0;
uint64_t dst_mem_base_gprs = 0;
for (size_t i = 0; i < argc; i++) {
switch (src[i].kind) {
case JIT_OPERAND_KIND_GPR:
src_gprs |= 1ULL << jit_gpr_regno(src[i].loc.gpr.gpr);
break;
case JIT_OPERAND_KIND_FPR:
case JIT_OPERAND_KIND_IMM:
case JIT_OPERAND_KIND_MEM:
break;
default:
abort();
}
switch (dst[i].kind) {
case JIT_OPERAND_KIND_GPR: {
ASSERT(dst[i].loc.gpr.addend == 0);
uint64_t bit = 1ULL << jit_gpr_regno(dst[i].loc.gpr.gpr);
ASSERT((dst_gprs & bit) == 0);
dst_gprs |= bit;
break;
}
case JIT_OPERAND_KIND_FPR: {
uint64_t bit = 1ULL << jit_fpr_regno(dst[i].loc.fpr);
ASSERT((dst_fprs & bit) == 0);
dst_fprs |= bit;
break;
}
case JIT_OPERAND_KIND_MEM: {
ASSERT(dst[i].loc.mem.addend == 0);
uint64_t bit = 1ULL << jit_gpr_regno(dst[i].loc.mem.base);
dst_mem_base_gprs |= bit;
break;
}
case JIT_OPERAND_KIND_IMM:
default:
abort();
break;
}
}
ASSERT(((src_gprs | dst_gprs) & dst_mem_base_gprs) == 0);
}
enum move_status status[argc];
for (size_t i = 0; i < argc; i++)
status[i] = TO_MOVE;
for (size_t i = 0; i < argc; i++)
if (status[i] == TO_MOVE)
move_one(_jit, dst, src, argc, status, i);
// Apply addends at the end. We could do it earlier in some cases but
// at least at the end we know that an in-place increment of one
// operand won't alias another.
for (size_t i = 0; i < argc; i++)
apply_addend(_jit, dst[i], src[i]);
}
size_t
jit_align_stack(jit_state_t *_jit, size_t expand)
{
size_t new_size = _jit->frame_size + expand;
// Align stack to double-word boundaries. This isn't really a
// principle but it does work for Aarch32, AArch64 and x86-64.
size_t alignment = __WORDSIZE * 2;
size_t aligned_size = (new_size + alignment - 1) & ~(alignment - 1);
size_t diff = aligned_size - _jit->frame_size;
if (diff)
jit_subi (_jit, JIT_SP, JIT_SP, diff);
_jit->frame_size = aligned_size;
return diff;
}
void
jit_shrink_stack(jit_state_t *_jit, size_t diff)
{
if (diff)
jit_addi (_jit, JIT_SP, JIT_SP, diff);
_jit->frame_size -= diff;
}
// Precondition: stack is already aligned.
static size_t
prepare_call_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
jit_operand_t dst[argc];
struct abi_arg_iterator iter;
// Compute shuffle destinations and space for spilled arguments.
reset_abi_arg_iterator(&iter, argc, args);
for (size_t i = 0; i < argc; i++)
next_abi_arg(&iter, &dst[i]);
// Reserve space for spilled arguments and ensure stack alignment.
size_t stack_size = jit_align_stack(_jit, iter.stack_size);
// Fix up SP-relative operands.
for (size_t i = 0; i < argc; i++) {
switch(args[i].kind) {
case JIT_OPERAND_KIND_GPR:
if (jit_same_gprs (args[i].loc.mem.base, JIT_SP))
args[i].loc.gpr.addend += stack_size;
break;
case JIT_OPERAND_KIND_MEM:
if (jit_same_gprs (args[i].loc.mem.base, JIT_SP))
args[i].loc.mem.offset += stack_size;
break;
default:
break;
}
}
jit_move_operands(_jit, dst, args, argc);
return stack_size;
}
void
jit_calli(jit_state_t *_jit, jit_pointer_t f, size_t argc, jit_operand_t args[])
{
size_t stack_bytes = prepare_call_args(_jit, argc, args);
calli(_jit, (jit_word_t)f);
jit_shrink_stack(_jit, stack_bytes);
}
void
jit_callr(jit_state_t *_jit, jit_gpr_t f, size_t argc, jit_operand_t args[])
{
size_t stack_bytes = prepare_call_args(_jit, argc, args);
callr(_jit, jit_gpr_regno(f));
jit_shrink_stack(_jit, stack_bytes);
}
void
jit_locate_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
struct abi_arg_iterator iter;
reset_abi_arg_iterator(&iter, argc, args);
for (size_t i = 0; i < argc; i++)
next_abi_arg(&iter, &args[i]);
}
/* Precondition: args are distinct locations of type GPR or FPR. All
addends of arg operands are zero. No GPR arg is SP. */
void
jit_load_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
jit_operand_t src[argc];
memcpy(src, args, sizeof(src[0]) * argc);
jit_locate_args(_jit, argc, src);
jit_move_operands(_jit, args, src, argc);
}

116
libguile/lightening/lightening/x86-cpu.c
View file

@ -254,6 +254,7 @@ rx(jit_state_t *_jit, int32_t rd, int32_t md,
static void
pushr(jit_state_t *_jit, int32_t r0)
{
_jit->frame_size += __WORDSIZE;
rex(_jit, 0, WIDE, 0, 0, r0);
ic(_jit, 0x50 | r7(r0));
}
@ -261,6 +262,7 @@ pushr(jit_state_t *_jit, int32_t r0)
static void
popr(jit_state_t *_jit, int32_t r0)
{
_jit->frame_size -= __WORDSIZE;
rex(_jit, 0, WIDE, 0, 0, r0);
ic(_jit, 0x58 | r7(r0));
}
@ -401,7 +403,7 @@ mov_addr(jit_state_t *_jit, int32_t r0)
rex(_jit, 0, WIDE, _NOREG, _NOREG, r0);
ic(_jit, 0xb8 | r7(r0));
ptrdiff_t inst_start = _jit->pc.uc - pc_start;
return jit_reloc(_jit, JIT_RELOC_ABSOLUTE, inst_start, 0);
return jit_reloc(_jit, JIT_RELOC_ABSOLUTE, inst_start);
}
static void
@ -657,15 +659,6 @@ testi(jit_state_t *_jit, int32_t r0, jit_word_t i0)
ii(_jit, i0);
}
static void
cc(jit_state_t *_jit, int32_t code, int32_t r0)
{
rex(_jit, 0, 0, _NOREG, _NOREG, r0);
ic(_jit, 0x0f);
ic(_jit, 0x90 | code);
mrm(_jit, 0x03, 0x00, r7(r0));
}
static void
negr(jit_state_t *_jit, int32_t r0, int32_t r1)
{
@ -1463,69 +1456,6 @@ xori(jit_state_t *_jit, int32_t r0, int32_t r1, jit_word_t i0)
}
}
static void
cr(jit_state_t *_jit, int32_t code, int32_t r0, int32_t r1, int32_t r2)
{
if (reg8_p(r0)) {
jit_bool_t same = r0 == r1 || r0 == r2;
if (!same)
ixorr(_jit, r0, r0);
icmpr(_jit, r1, r2);
if (same)
imovi(_jit, r0, 0);
cc(_jit, code, r0);
} else {
jit_gpr_t reg = get_temp_gpr(_jit);
ixorr(_jit, jit_gpr_regno(reg), jit_gpr_regno(reg));
icmpr(_jit, r1, r2);
cc(_jit, code, jit_gpr_regno(reg));
movr(_jit, r0, jit_gpr_regno(reg));
unget_temp_gpr(_jit);
}
}
static void
ci(jit_state_t *_jit, int32_t code, int32_t r0, int32_t r1, jit_word_t i0)
{
if (reg8_p(r0)) {
jit_bool_t same = r0 == r1;
if (!same)
ixorr(_jit, r0, r0);
icmpi(_jit, r1, i0);
if (same)
imovi(_jit, r0, 0);
cc(_jit, code, r0);
} else {
jit_gpr_t reg = get_temp_gpr(_jit);
ixorr(_jit, jit_gpr_regno(reg), jit_gpr_regno(reg));
icmpi(_jit, r1, i0);
cc(_jit, code, jit_gpr_regno(reg));
movr(_jit, r0, jit_gpr_regno(reg));
unget_temp_gpr(_jit);
}
}
static void
ci0(jit_state_t *_jit, int32_t code, int32_t r0, int32_t r1)
{
if (reg8_p(r0)) {
jit_bool_t same = r0 == r1;
if (!same)
ixorr(_jit, r0, r0);
testr(_jit, r1, r1);
if (same)
imovi(_jit, r0, 0);
cc(_jit, code, r0);
} else {
jit_gpr_t reg = get_temp_gpr(_jit);
ixorr(_jit, jit_gpr_regno(reg), jit_gpr_regno(reg));
testr(_jit, r1, r1);
cc(_jit, code, jit_gpr_regno(reg));
movr(_jit, r0, jit_gpr_regno(reg));
unget_temp_gpr(_jit);
}
}
static void
extr_c(jit_state_t *_jit, int32_t r0, int32_t r1)
{
@ -2253,7 +2183,7 @@ static jit_reloc_t
jccs(jit_state_t *_jit, int32_t code)
{
ic(_jit, 0x70 | code);
return jit_reloc(_jit, JIT_RELOC_REL8, 1, 0);
return jit_reloc(_jit, JIT_RELOC_REL8, 1);
}
static jit_reloc_t
@ -2261,7 +2191,26 @@ jcc(jit_state_t *_jit, int32_t code)
{
ic(_jit, 0x0f);
ic(_jit, 0x80 | code);
return jit_reloc(_jit, JIT_RELOC_REL32, 2, 0);
return jit_reloc(_jit, JIT_RELOC_REL32, 2);
}
static void
jcci(jit_state_t *_jit, int32_t code, jit_word_t i0)
{
ptrdiff_t rel8 = i0 - (_jit->pc.w + 1 + 1);
ptrdiff_t rel32 = i0 - (_jit->pc.w + 2 + 4);
if (INT8_MIN <= rel8 && rel8 <= INT8_MAX)
{
ic(_jit, 0x70 | code);
ic(_jit, rel8);
}
else
{
ASSERT(INT32_MIN <= rel32 && rel32 <= INT32_MAX);
ic(_jit, 0x0f);
ic(_jit, 0x80 | code);
ii(_jit, rel32);
}
}
#define DEFINE_JUMPS(cc, CC, code) \
@ -2664,8 +2613,14 @@ jmpr(jit_state_t *_jit, int32_t r0)
static void
jmpi(jit_state_t *_jit, jit_word_t i0)
{
ptrdiff_t rel8 = i0 - (_jit->pc.w + 1 + 1);
ptrdiff_t rel32 = i0 - (_jit->pc.w + 1 + 4);
if (INT32_MIN <= rel32 && rel32 <= INT32_MAX)
if (INT8_MIN <= rel8 && rel8 <= INT8_MAX)
{
ic(_jit, 0xeb);
ic(_jit, rel8);
}
else if (INT32_MIN <= rel32 && rel32 <= INT32_MAX)
{
ic(_jit, 0xe9);
ii(_jit, rel32);
@ -2683,14 +2638,7 @@ static jit_reloc_t
jmp(jit_state_t *_jit)
{
ic(_jit, 0xe9);
return jit_reloc(_jit, JIT_RELOC_REL32, 1, 0);
}
static jit_reloc_t
jmpsi(jit_state_t *_jit)
{
ic(_jit, 0xeb);
return jit_reloc(_jit, JIT_RELOC_REL8, 1, 0);
return jit_reloc(_jit, JIT_RELOC_REL32, 1);
}
static void

552
libguile/lightening/lightening/x86.c
View file

@ -214,12 +214,6 @@ jit_init(jit_state_t *_jit)
return jit_cpu.sse2;
}
void
jit_epilog(jit_state_t *_jit)
{
/* TODO: Restore registers. */
}
static jit_bool_t
is_fpr_arg(enum jit_operand_abi arg)
{
@ -249,426 +243,6 @@ is_gpr_arg(enum jit_operand_abi arg)
return !is_fpr_arg(arg);
}
static void
abi_imm_to_gpr(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t dst,
intptr_t imm)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
ASSERT(0 <= imm);
ASSERT(imm <= UINT8_MAX);
break;
case JIT_OPERAND_ABI_INT8:
ASSERT(INT8_MIN <= imm);
ASSERT(imm <= INT8_MAX);
break;
case JIT_OPERAND_ABI_UINT16:
ASSERT(0 <= imm);
ASSERT(imm <= UINT16_MAX);
break;
case JIT_OPERAND_ABI_INT16:
ASSERT(INT16_MIN <= imm);
ASSERT(imm <= INT16_MAX);
break;
case JIT_OPERAND_ABI_UINT32:
ASSERT(0 <= imm);
ASSERT(imm <= UINT32_MAX);
break;
case JIT_OPERAND_ABI_INT32:
ASSERT(INT32_MIN <= imm);
ASSERT(imm <= INT32_MAX);
break;
#if __WORDSIZE > 32
case JIT_OPERAND_ABI_UINT64:
case JIT_OPERAND_ABI_INT64:
break;
#endif
case JIT_OPERAND_ABI_POINTER:
break;
default:
abort();
}
jit_movi (_jit, dst, imm);
}
static void
abi_gpr_to_mem(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t base, ptrdiff_t offset, jit_gpr_t src)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
case JIT_OPERAND_ABI_INT8:
jit_stxi_c(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_UINT16:
case JIT_OPERAND_ABI_INT16:
jit_stxi_s(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_UINT32:
case JIT_OPERAND_ABI_INT32:
#if __WORDSIZE == 32
case JIT_OPERAND_ABI_POINTER:
#endif
jit_stxi_i(_jit, offset, base, src);
break;
#if __WORDSIZE == 64
case JIT_OPERAND_ABI_UINT64:
case JIT_OPERAND_ABI_INT64:
case JIT_OPERAND_ABI_POINTER:
jit_stxi_l(_jit, offset, base, src);
break;
#endif
default:
abort();
}
}
static void
abi_fpr_to_mem(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t base, ptrdiff_t offset, jit_fpr_t src)
{
switch (abi) {
case JIT_OPERAND_ABI_FLOAT:
jit_stxi_f(_jit, offset, base, src);
break;
case JIT_OPERAND_ABI_DOUBLE:
jit_stxi_d(_jit, offset, base, src);
break;
default:
abort();
}
}
static void
abi_mem_to_gpr(jit_state_t *_jit, enum jit_operand_abi abi,
jit_gpr_t dst, jit_gpr_t base, ptrdiff_t offset)
{
switch (abi) {
case JIT_OPERAND_ABI_UINT8:
jit_ldxi_uc(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT8:
jit_ldxi_c(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT16:
jit_ldxi_us(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT16:
jit_ldxi_s(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT32:
jit_ldxi_ui(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT32:
jit_ldxi_i(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_UINT64:
jit_ldxi_l(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_INT64:
jit_ldxi_l(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_POINTER:
jit_ldxi_l(_jit, dst, base, offset);
break;
default:
abort();
}
}
static void
abi_mem_to_fpr(jit_state_t *_jit, enum jit_operand_abi abi,
jit_fpr_t dst, jit_gpr_t base, ptrdiff_t offset)
{
switch (abi) {
case JIT_OPERAND_ABI_FLOAT:
jit_ldxi_f(_jit, dst, base, offset);
break;
case JIT_OPERAND_ABI_DOUBLE:
jit_ldxi_d(_jit, dst, base, offset);
break;
default:
abort();
}
}
static void
abi_imm_to_mem(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t base,
ptrdiff_t offset, intmax_t imm)
{
ASSERT(!is_fpr_arg(abi));
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_imm_to_gpr(_jit, abi, tmp, imm);
abi_gpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_gpr(_jit);
}
static void
abi_mem_to_mem(jit_state_t *_jit, enum jit_operand_abi abi, jit_gpr_t base,
ptrdiff_t offset, jit_gpr_t src_base, ptrdiff_t src_offset)
{
if (is_gpr_arg (abi)) {
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_mem_to_gpr(_jit, abi, tmp, src_base, src_offset);
abi_gpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_gpr(_jit);
} else {
jit_fpr_t tmp = get_temp_xpr(_jit);
abi_mem_to_fpr(_jit, abi, tmp, src_base, src_offset);
abi_fpr_to_mem(_jit, abi, base, offset, tmp);
unget_temp_xpr(_jit);
}
}
#define MOVE_KIND(a, b) ((((int) a) << 4) | ((int) b))
#define MOVE_KIND_ENUM(a, b) \
MOVE_##a##_TO_##b = MOVE_KIND(JIT_OPERAND_KIND_##a, JIT_OPERAND_KIND_##b)
enum move_kind {
MOVE_KIND_ENUM(IMM, GPR),
MOVE_KIND_ENUM(GPR, GPR),
MOVE_KIND_ENUM(MEM, GPR),
MOVE_KIND_ENUM(FPR, FPR),
MOVE_KIND_ENUM(MEM, FPR),
MOVE_KIND_ENUM(IMM, MEM),
MOVE_KIND_ENUM(GPR, MEM),
MOVE_KIND_ENUM(FPR, MEM),
MOVE_KIND_ENUM(MEM, MEM)
};
#undef MOVE_KIND_ENUM
static void
move_operand(jit_state_t *_jit, jit_operand_t dst, jit_operand_t src)
{
switch (MOVE_KIND (src.kind, dst.kind)) {
case MOVE_IMM_TO_GPR:
return abi_imm_to_gpr(_jit, src.abi, dst.loc.gpr.gpr, src.loc.imm);
case MOVE_GPR_TO_GPR:
return jit_movr(_jit, dst.loc.gpr.gpr, src.loc.gpr.gpr);
case MOVE_MEM_TO_GPR:
return abi_mem_to_gpr(_jit, src.abi, dst.loc.gpr.gpr, src.loc.mem.base,
src.loc.mem.offset);
case MOVE_FPR_TO_FPR:
return jit_movr_d(_jit, dst.loc.fpr, src.loc.fpr);
case MOVE_MEM_TO_FPR:
return abi_mem_to_fpr(_jit, src.abi, dst.loc.fpr, src.loc.mem.base,
src.loc.mem.offset);
case MOVE_IMM_TO_MEM:
return abi_imm_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.imm);
case MOVE_GPR_TO_MEM:
return abi_gpr_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.gpr.gpr);
case MOVE_FPR_TO_MEM:
return abi_fpr_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.fpr);
case MOVE_MEM_TO_MEM:
return abi_mem_to_mem(_jit, src.abi, dst.loc.mem.base, dst.loc.mem.offset,
src.loc.mem.base, src.loc.mem.offset);
default:
abort();
}
}
// A direct transliteration of "Tilting at windmills with Coq: formal
// verification of a compilation algorithm for parallel moves" by
// Laurence Rideau, Bernard Paul Serpette, and Xavier Leroy:
// https://xavierleroy.org/publi/parallel-move.pdf
enum move_status { TO_MOVE, BEING_MOVED, MOVED };
static inline int
already_in_place(jit_operand_t src, jit_operand_t dst)
{
switch (MOVE_KIND(src.kind, dst.kind)) {
case MOVE_GPR_TO_GPR:
return jit_same_gprs (src.loc.gpr.gpr, dst.loc.gpr.gpr);
case MOVE_FPR_TO_FPR:
return jit_same_fprs (src.loc.fpr, dst.loc.fpr);
case MOVE_MEM_TO_MEM:
return jit_same_gprs (src.loc.mem.base, dst.loc.mem.base) &&
src.loc.mem.offset == dst.loc.mem.offset;
default:
return 0;
}
}
static inline int
write_would_clobber(jit_operand_t src, jit_operand_t dst)
{
if (already_in_place (src, dst))
return 1;
if (MOVE_KIND(src.kind, dst.kind) == MOVE_MEM_TO_GPR)
return jit_same_gprs(src.loc.mem.base, dst.loc.gpr.gpr);
return 0;
}
static inline ptrdiff_t
operand_addend(jit_operand_t op)
{
switch (op.kind) {
case JIT_OPERAND_KIND_GPR:
return op.loc.gpr.addend;
case JIT_OPERAND_KIND_MEM:
return op.loc.mem.addend;
default:
abort();
}
}
static void
move_one(jit_state_t *_jit, jit_operand_t *dst, jit_operand_t *src,
size_t argc, enum move_status *status, size_t i)
{
int tmp_gpr = 0, tmp_fpr = 0;
if (already_in_place(src[i], dst[i]))
return;
status[i] = BEING_MOVED;
for (size_t j = 0; j < argc; j++) {
if (write_would_clobber(src[j], dst[i])) {
switch (status[j]) {
case TO_MOVE:
move_one(_jit, dst, src, argc, status, j);
break;
case BEING_MOVED: {
jit_operand_t tmp;
if (is_fpr_arg (src[j].kind)) {
tmp_fpr = 1;
tmp = jit_operand_fpr(src[j].abi, get_temp_xpr(_jit));
} else {
tmp_gpr = 1;
/* Preserve addend, if any, from source operand, to be applied
at the end. */
tmp = jit_operand_gpr_with_addend(src[j].abi, get_temp_gpr(_jit),
operand_addend(src[j]));
}
move_operand (_jit, tmp, src[j]);
src[j] = tmp;
break;
}
case MOVED:
break;
default:
abort ();
}
}
}
move_operand (_jit, dst[i], src[i]);
status[i] = MOVED;
if (tmp_gpr)
unget_temp_gpr(_jit);
else if (tmp_fpr)
unget_temp_xpr(_jit);
}
static void
apply_addend(jit_state_t *_jit, jit_operand_t dst, jit_operand_t src)
{
switch (MOVE_KIND(src.kind, dst.kind)) {
case MOVE_GPR_TO_GPR:
case MOVE_MEM_TO_GPR:
if (operand_addend(src))
jit_addi(_jit, dst.loc.gpr.gpr, dst.loc.gpr.gpr, operand_addend(src));
break;
case MOVE_GPR_TO_MEM:
case MOVE_MEM_TO_MEM:
if (operand_addend(src)) {
jit_gpr_t tmp = get_temp_gpr(_jit);
abi_mem_to_gpr(_jit, dst.abi, tmp, dst.loc.mem.base, dst.loc.mem.offset);
jit_addi(_jit, tmp, tmp, operand_addend(src));
abi_gpr_to_mem(_jit, dst.abi, dst.loc.mem.base, dst.loc.mem.offset, tmp);
}
break;
default:
break;
}
}
/* Preconditions: No dest operand is IMM. No dest operand aliases
another dest operand. No dest MEM operand uses a base register which
is used as a dest GPR. No dst operand has an addend. The registers
returned by get_temp_gpr and get_temp_fpr do not appear in source or
dest args. */
void
jit_move_operands(jit_state_t *_jit, jit_operand_t *dst, jit_operand_t *src,
size_t argc)
{
// Check preconditions, except the condition about tmp registers.
{
uint64_t src_gprs = 0;
uint64_t dst_gprs = 0;
uint64_t dst_fprs = 0;
uint64_t dst_mem_base_gprs = 0;
for (size_t i = 0; i < argc; i++) {
switch (src[i].kind) {
case JIT_OPERAND_KIND_GPR:
src_gprs |= 1ULL << jit_gpr_regno(src[i].loc.gpr.gpr);
break;
case JIT_OPERAND_KIND_FPR:
case JIT_OPERAND_KIND_IMM:
case JIT_OPERAND_KIND_MEM:
break;
default:
abort();
}
switch (dst[i].kind) {
case JIT_OPERAND_KIND_GPR: {
ASSERT(dst[i].loc.gpr.addend == 0);
uint64_t bit = 1ULL << jit_gpr_regno(dst[i].loc.gpr.gpr);
ASSERT((dst_gprs & bit) == 0);
dst_gprs |= bit;
break;
}
case JIT_OPERAND_KIND_FPR: {
uint64_t bit = 1ULL << jit_fpr_regno(dst[i].loc.fpr);
ASSERT((dst_fprs & bit) == 0);
dst_fprs |= bit;
break;
}
case JIT_OPERAND_KIND_MEM: {
ASSERT(dst[i].loc.mem.addend == 0);
uint64_t bit = 1ULL << jit_gpr_regno(dst[i].loc.mem.base);
dst_mem_base_gprs |= bit;
break;
}
case JIT_OPERAND_KIND_IMM:
default:
abort();
break;
}
}
ASSERT(((src_gprs | dst_gprs) & dst_mem_base_gprs) == 0);
}
enum move_status status[argc];
for (size_t i = 0; i < argc; i++)
status[i] = TO_MOVE;
for (size_t i = 0; i < argc; i++)
if (status[i] == TO_MOVE)
move_one(_jit, dst, src, argc, status, i);
// Apply addends at the end. We could do it earlier in some cases but
// at least at the end we know that an in-place increment of one
// operand won't alias another.
for (size_t i = 0; i < argc; i++)
apply_addend(_jit, dst[i], src[i]);
}
static const jit_gpr_t abi_gpr_args[] = {
#if __X32
/* No GPRs in args. */
@ -771,100 +345,48 @@ next_abi_arg(struct abi_arg_iterator *iter, jit_operand_t *arg)
iter->arg_idx++;
}
// Precondition: stack is already aligned.
static size_t
prepare_call_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
jit_operand_t dst[argc];
struct abi_arg_iterator iter;
// Compute shuffle destinations and space for spilled arguments.
reset_abi_arg_iterator(&iter, argc, args);
for (size_t i = 0; i < argc; i++)
next_abi_arg(&iter, &dst[i]);
size_t stack_size = iter.stack_size;
// Reserve space for spilled arguments, and fix up SP-relative
// operands.
if (stack_size)
{
// Align stack to 16-byte boundaries on 64-bit targets.
if (__WORDSIZE == 64)
stack_size = (stack_size + 15) & ~15;
jit_subi(_jit, JIT_SP, JIT_SP, stack_size);
for (size_t i = 0; i < argc; i++) {
switch(args[i].kind) {
case JIT_OPERAND_KIND_GPR:
if (jit_same_gprs (args[i].loc.mem.base, JIT_SP))
args[i].loc.gpr.addend += stack_size;
break;
case JIT_OPERAND_KIND_MEM:
if (jit_same_gprs (args[i].loc.mem.base, JIT_SP))
args[i].loc.mem.offset += stack_size;
break;
default:
break;
}
}
}
jit_move_operands(_jit, dst, args, argc);
return stack_size;
}
void
jit_calli(jit_state_t *_jit, jit_pointer_t f, size_t argc, jit_operand_t args[])
{
size_t spill_size = prepare_call_args(_jit, argc, args);
calli(_jit, (jit_word_t)f);
if (spill_size)
jit_addi(_jit, JIT_SP, JIT_SP, spill_size);
}
void
jit_callr(jit_state_t *_jit, jit_gpr_t f, size_t argc, jit_operand_t args[])
{
size_t spill_size = prepare_call_args(_jit, argc, args);
callr(_jit, jit_gpr_regno(f));
if (spill_size)
jit_addi(_jit, JIT_SP, JIT_SP, spill_size);
}
void
jit_locate_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
struct abi_arg_iterator iter;
reset_abi_arg_iterator(&iter, argc, args);
for (size_t i = 0; i < argc; i++)
next_abi_arg(&iter, &args[i]);
}
/* Precondition: args are distinct locations of type GPR or FPR. All
addends of arg operands are zero. No GPR arg is SP. */
void
jit_load_args(jit_state_t *_jit, size_t argc, jit_operand_t args[])
{
jit_operand_t src[argc];
memcpy(src, args, sizeof(src[0]) * argc);
jit_locate_args(_jit, argc, src);
jit_move_operands(_jit, args, src, argc);
}
void
jit_flush(void *fptr, void *tptr)
{
}
static void
jit_try_shorten(jit_state_t *_jit, jit_reloc_t reloc)
jit_try_shorten(jit_state_t *_jit, jit_reloc_t reloc, jit_pointer_t addr)
{
uint8_t *loc = _jit->start + reloc.offset;
uint8_t *start = loc - reloc.inst_start_offset;
jit_imm_t i0 = (jit_imm_t)addr;
switch (reloc.kind)
{
case JIT_RELOC_ABSOLUTE: {
_jit->pc.uc = start;
ASSERT((loc[-1] & ~7) == 0xb8); // MOVI
int32_t r0 = loc[-1] & 7;
if (start != loc - 1) {
ASSERT(start == loc - 2);
r0 |= (loc[-2] & 1) << 3;
}
return movi(_jit, r0, i0);
}
case JIT_RELOC_REL8:
ASSERT((loc[-1] & ~0xf) == 0x70 || loc[-1] == 0xeb); // JCCSI or JMPSI
/* Nothing useful to do. */
return;
case JIT_RELOC_REL16:
/* We don't emit these. */
abort ();
case JIT_RELOC_REL32:
_jit->pc.uc = start;
if (start[0] == 0xe9) { // JMP
return jmpi(_jit, i0);
}
ASSERT(start[0] == 0x0f); // JCC
return jcci(_jit, start[1] & ~0x80, i0);
case JIT_RELOC_REL64:
/* We don't emit these. */
abort ();
default:
abort ();
}
}