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tcg-i386: Use new return-argument ld/st helpers
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Discontinue the jump-around-jump-to-jump scheme, trading it for a single
immediate move instruction.  The two extra jumps always consume 7 bytes,
whereas the immediate move is either 5 or 7 bytes depending on where the
code_gen_buffer gets located.

Signed-off-by: Richard Henderson <rth@twiddle.net>
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@rth7680
rth7680 committed Aug 26, 2013
1 parent aac1fb0 commit 401c227
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Showing 2 changed files with 49 additions and 67 deletions.
13 changes: 2 additions & 11 deletions include/exec/exec-all.h
View file
Expand Up @@ -326,18 +326,9 @@ extern uintptr_t tci_tb_ptr;
(6) jump to corresponding code of the next of fast path
*/
# if defined(__i386__) || defined(__x86_64__)
/* To avoid broken disassembling, long jmp is used for embedding fast path pc,
so that the destination is the next code of fast path, though this jmp is
never executed.
call MMU helper
jmp POST_PROC (2byte) <- GETRA()
jmp NEXT_CODE (5byte)
POST_PROCESS ... <- GETRA() + 7
*/
# define GETRA() ((uintptr_t)__builtin_return_address(0))
# define GETPC_LDST() ((uintptr_t)(GETRA() + 7 + \
*(int32_t *)((void *)GETRA() + 3) - 1))
/* The return address argument for ldst is passed directly. */
# define GETPC_LDST() (abort(), 0)
# elif defined (_ARCH_PPC) && !defined (_ARCH_PPC64)
# define GETRA() ((uintptr_t)__builtin_return_address(0))
# define GETPC_LDST() ((uintptr_t) ((*(int32_t *)(GETRA() - 4)) - 1))
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103 changes: 47 additions & 56 deletions tcg/i386/tcg-target.c
View file
Expand Up @@ -190,11 +190,11 @@ static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str)
/* qemu_ld/st address constraint */
case 'L':
ct->ct |= TCG_CT_REG;
#if TCG_TARGET_REG_BITS == 64
if (TCG_TARGET_REG_BITS == 64) {
tcg_regset_set32(ct->u.regs, 0, 0xffff);
#else
} else {
tcg_regset_set32(ct->u.regs, 0, 0xff);
#endif
}
tcg_regset_reset_reg(ct->u.regs, TCG_REG_L0);
tcg_regset_reset_reg(ct->u.regs, TCG_REG_L1);
break;
Expand Down Expand Up @@ -1025,22 +1025,24 @@ static void tcg_out_jmp(TCGContext *s, tcg_target_long dest)

#include "exec/softmmu_defs.h"

/* helper signature: helper_ld_mmu(CPUState *env, target_ulong addr,
int mmu_idx) */
static const void *qemu_ld_helpers[4] = {
helper_ldb_mmu,
helper_ldw_mmu,
helper_ldl_mmu,
helper_ldq_mmu,
/* helper signature: helper_ret_ld_mmu(CPUState *env, target_ulong addr,
* int mmu_idx, uintptr_t ra)
*/
static const void * const qemu_ld_helpers[4] = {
helper_ret_ldb_mmu,
helper_ret_ldw_mmu,
helper_ret_ldl_mmu,
helper_ret_ldq_mmu,
};

/* helper signature: helper_st_mmu(CPUState *env, target_ulong addr,
uintxx_t val, int mmu_idx) */
static const void *qemu_st_helpers[4] = {
helper_stb_mmu,
helper_stw_mmu,
helper_stl_mmu,
helper_stq_mmu,
/* helper signature: helper_ret_st_mmu(CPUState *env, target_ulong addr,
* uintxx_t val, int mmu_idx, uintptr_t ra)
*/
static const void * const qemu_st_helpers[4] = {
helper_ret_stb_mmu,
helper_ret_stw_mmu,
helper_ret_stl_mmu,
helper_ret_stq_mmu,
};

static void add_qemu_ldst_label(TCGContext *s,
Expand Down Expand Up @@ -1468,6 +1470,12 @@ static void add_qemu_ldst_label(TCGContext *s,
}
}

/* See the GETPC definition in include/exec/exec-all.h. */
static inline uintptr_t do_getpc(uint8_t *raddr)
{
return (uintptr_t)raddr - 1;
}

/*
* Generate code for the slow path for a load at the end of block
*/
Expand Down Expand Up @@ -1499,33 +1507,20 @@ static void tcg_out_qemu_ld_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
}

tcg_out_sti(s, TCG_TYPE_I32, TCG_REG_ESP, ofs, l->mem_index);
ofs += 4;

tcg_out_sti(s, TCG_TYPE_I32, TCG_REG_ESP, ofs, do_getpc(l->raddr));
} else {
tcg_out_mov(s, TCG_TYPE_I64, tcg_target_call_iarg_regs[0], TCG_AREG0);
tcg_out_mov(s, TCG_TYPE_PTR, tcg_target_call_iarg_regs[0], TCG_AREG0);
/* The second argument is already loaded with addrlo. */
tcg_out_movi(s, TCG_TYPE_I32, tcg_target_call_iarg_regs[2],
l->mem_index);
tcg_out_movi(s, TCG_TYPE_PTR, tcg_target_call_iarg_regs[3],
do_getpc(l->raddr));
}

/* Code generation of qemu_ld/st's slow path calling MMU helper
PRE_PROC ...
call MMU helper
jmp POST_PROC (2b) : short forward jump <- GETRA()
jmp next_code (5b) : dummy long backward jump which is never executed
POST_PROC ... : do post-processing <- GETRA() + 7
jmp next_code : jump to the code corresponding to next IR of qemu_ld/st
*/

tcg_out_calli(s, (tcg_target_long)qemu_ld_helpers[s_bits]);

/* Jump to post-processing code */
tcg_out8(s, OPC_JMP_short);
tcg_out8(s, 5);
/* Dummy backward jump having information of fast path'pc for MMU helpers */
tcg_out8(s, OPC_JMP_long);
*(int32_t *)s->code_ptr = (int32_t)(l->raddr - s->code_ptr - 4);
s->code_ptr += 4;

data_reg = l->datalo_reg;
switch(opc) {
case 0 | 4:
Expand Down Expand Up @@ -1606,36 +1601,32 @@ static void tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
}

tcg_out_sti(s, TCG_TYPE_I32, TCG_REG_ESP, ofs, l->mem_index);
ofs += 4;

tcg_out_sti(s, TCG_TYPE_I32, TCG_REG_ESP, ofs, do_getpc(l->raddr));
} else {
tcg_out_mov(s, TCG_TYPE_I64, tcg_target_call_iarg_regs[0], TCG_AREG0);
uintptr_t pc;

tcg_out_mov(s, TCG_TYPE_PTR, tcg_target_call_iarg_regs[0], TCG_AREG0);
/* The second argument is already loaded with addrlo. */
tcg_out_mov(s, (opc == 3 ? TCG_TYPE_I64 : TCG_TYPE_I32),
tcg_target_call_iarg_regs[2], l->datalo_reg);
tcg_out_movi(s, TCG_TYPE_I32, tcg_target_call_iarg_regs[3],
l->mem_index);
}

/* Code generation of qemu_ld/st's slow path calling MMU helper
PRE_PROC ...
call MMU helper
jmp POST_PROC (2b) : short forward jump <- GETRA()
jmp next_code (5b) : dummy long backward jump which is never executed
POST_PROC ... : do post-processing <- GETRA() + 7
jmp next_code : jump to the code corresponding to next IR of qemu_ld/st
*/
pc = do_getpc(l->raddr);
if (ARRAY_SIZE(tcg_target_call_iarg_regs) > 4) {
tcg_out_movi(s, TCG_TYPE_PTR, tcg_target_call_iarg_regs[4], pc);
} else if (pc == (int32_t)pc) {
tcg_out_sti(s, TCG_TYPE_PTR, TCG_REG_ESP, 0, pc);
} else {
tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_RAX, pc);
tcg_out_st(s, TCG_TYPE_PTR, TCG_REG_RAX, TCG_REG_ESP, 0);
}
}

tcg_out_calli(s, (tcg_target_long)qemu_st_helpers[s_bits]);

/* Jump to post-processing code */
tcg_out8(s, OPC_JMP_short);
tcg_out8(s, 5);
/* Dummy backward jump having information of fast path'pc for MMU helpers */
tcg_out8(s, OPC_JMP_long);
*(int32_t *)s->code_ptr = (int32_t)(l->raddr - s->code_ptr - 4);
s->code_ptr += 4;

/* Jump to the code corresponding to next IR of qemu_st */
tcg_out_jmp(s, (tcg_target_long)l->raddr);
}

Expand Down

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