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tcg/i386: Precompute all guest_base parameters 

These values are constant between all qemu_ld/st invocations;
there is no need to figure this out each time.  If we cannot
use a segment or an offset directly for guest_base, load the
value into a register in the prologue.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2018-12-03 09:22:57 -06:00
parent 4810d96f03
commit 913c2bddc2
1 changed files with 40 additions and 61 deletions
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101
tcg/i386/tcg-target.inc.c
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@ -1857,22 +1857,31 @@ static void tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
tcg_out_push(s, retaddr);
tcg_out_jmp(s, qemu_st_helpers[opc & (MO_BSWAP | MO_SIZE)]);
}
#elif defined(__x86_64__) && defined(__linux__)
# include <asm/prctl.h>
# include <sys/prctl.h>
#elif TCG_TARGET_REG_BITS == 32
# define x86_guest_base_seg 0
# define x86_guest_base_index -1
# define x86_guest_base_offset guest_base
#else
static int x86_guest_base_seg;
static int x86_guest_base_index = -1;
static int32_t x86_guest_base_offset;
# if defined(__x86_64__) && defined(__linux__)
# include <asm/prctl.h>
# include <sys/prctl.h>
int arch_prctl(int code, unsigned long addr);
static int guest_base_flags;
static inline void setup_guest_base_seg(void)
static inline int setup_guest_base_seg(void)
{
if (arch_prctl(ARCH_SET_GS, guest_base) == 0) {
guest_base_flags = P_GS;
return P_GS;
}
return 0;
}
#else
# define guest_base_flags 0
static inline void setup_guest_base_seg(void) { }
# else
static inline int setup_guest_base_seg(void)
{
return 0;
}
# endif
#endif /* SOFTMMU */
static void tcg_out_qemu_ld_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
@ -2011,27 +2020,9 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg *args, bool is64)
add_qemu_ldst_label(s, true, is64, oi, datalo, datahi, addrlo, addrhi,
s->code_ptr, label_ptr);
#else
{
int32_t offset = guest_base;
int index = -1;
int seg = 0;
/*
* Recall we store 32-bit values zero-extended. No need for
* further manual extension or an addr32 (0x67) prefix.
*/
if (guest_base == 0 || guest_base_flags) {
seg = guest_base_flags;
offset = 0;
} else if (TCG_TARGET_REG_BITS == 64 && offset != guest_base) {
tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_L1, guest_base);
index = TCG_REG_L1;
offset = 0;
}
tcg_out_qemu_ld_direct(s, datalo, datahi,
addrlo, index, offset, seg, is64, opc);
}
tcg_out_qemu_ld_direct(s, datalo, datahi, addrlo, x86_guest_base_index,
x86_guest_base_offset, x86_guest_base_seg,
is64, opc);
#endif
}
@ -2147,28 +2138,8 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg *args, bool is64)
add_qemu_ldst_label(s, false, is64, oi, datalo, datahi, addrlo, addrhi,
s->code_ptr, label_ptr);
#else
{
int32_t offset = guest_base;
int index = -1;
int seg = 0;
/*
* Recall we store 32-bit values zero-extended. No need for
* further manual extension or an addr32 (0x67) prefix.
*/
if (guest_base == 0 || guest_base_flags) {
seg = guest_base_flags;
offset = 0;
} else if (TCG_TARGET_REG_BITS == 64 && offset != guest_base) {
/* ??? Note that we require L0 free for bswap. */
tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_L1, guest_base);
index = TCG_REG_L1;
offset = 0;
}
tcg_out_qemu_st_direct(s, datalo, datahi,
addrlo, index, offset, seg, opc);
}
tcg_out_qemu_st_direct(s, datalo, datahi, addrlo, x86_guest_base_index,
x86_guest_base_offset, x86_guest_base_seg, opc);
#endif
}
@ -3415,6 +3386,21 @@ static void tcg_target_qemu_prologue(TCGContext *s)
(ARRAY_SIZE(tcg_target_callee_save_regs) + 2) * 4
+ stack_addend);
#else
# if !defined(CONFIG_SOFTMMU) && TCG_TARGET_REG_BITS == 64
if (guest_base) {
int seg = setup_guest_base_seg();
if (seg != 0) {
x86_guest_base_seg = seg;
} else if (guest_base == (int32_t)guest_base) {
x86_guest_base_offset = guest_base;
} else {
/* Choose R12 because, as a base, it requires a SIB byte. */
x86_guest_base_index = TCG_REG_R12;
tcg_out_mov(s, TCG_TYPE_PTR, x86_guest_base_index, guest_base);
tcg_regset_set_reg(s->reserved_regs, x86_guest_base_index);
}
}
# endif
tcg_out_mov(s, TCG_TYPE_PTR, TCG_AREG0, tcg_target_call_iarg_regs[0]);
tcg_out_addi(s, TCG_REG_ESP, -stack_addend);
/* jmp *tb. */
@ -3440,13 +3426,6 @@ static void tcg_target_qemu_prologue(TCGContext *s)
tcg_out_pop(s, tcg_target_callee_save_regs[i]);
}
tcg_out_opc(s, OPC_RET, 0, 0, 0);
#if !defined(CONFIG_SOFTMMU)
/* Try to set up a segment register to point to guest_base. */
if (guest_base) {
setup_guest_base_seg();
}
#endif
}
static void tcg_out_nop_fill(tcg_insn_unit *p, int count)