Commit 913c2bdd authored by Richard Henderson's avatar Richard Henderson
Browse files

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: default avatarEmilio G. Cota <cota@braap.org>
Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
parent 4810d96f

tcg/i386/tcg-target.inc.c

+40 −61
Original line number Diff line number Diff line
@@ -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__)

#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) { }

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)