Re: [Qemu-devel] [PATCH 17/18] tcg-i386: Adjust tcg_out_tlb_load for x32

[Aurelien Jarno <aurelien@aurel32.net>]

On Thu, Aug 22, 2013 at 09:58:48AM -0700, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/i386/tcg-target.c | 35 +++++++++++++++++++++--------------
>  1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
> index f3083b8..dfda76e 100644
> --- a/tcg/i386/tcg-target.c
> +++ b/tcg/i386/tcg-target.c
> @@ -1061,33 +1061,40 @@ static inline void tcg_out_tlb_load(TCGContext *s, int addrlo_idx,
>      const int addrlo = args[addrlo_idx];
>      const int r0 = TCG_REG_L0;
>      const int r1 = TCG_REG_L1;
> -    TCGType type = TCG_TYPE_I32;
> -    int rexw = 0;
> +    TCGType ttype = TCG_TYPE_I32;
> +    TCGType htype = TCG_TYPE_I32;
> +    int trexw = 0, hrexw = 0;
>  
> -    if (TCG_TARGET_REG_BITS == 64 && TARGET_LONG_BITS == 64) {
> -        type = TCG_TYPE_I64;
> -        rexw = P_REXW;
> +    if (TCG_TARGET_REG_BITS == 64) {
> +        if (TARGET_LONG_BITS == 64) {
> +            ttype = TCG_TYPE_I64;
> +            trexw = P_REXW;
> +        }
> +        if (sizeof(void *) == 8) {
> +            htype = TCG_TYPE_I64;
> +            hrexw = P_REXW;
> +        }
>      }
>  
> -    tcg_out_mov(s, type, r0, addrlo);
> -    tcg_out_mov(s, type, r1, addrlo);
> +    tcg_out_mov(s, htype, r0, addrlo);
> +    tcg_out_mov(s, ttype, r1, addrlo);
>  
> -    tcg_out_shifti(s, SHIFT_SHR + rexw, r0,
> +    tcg_out_shifti(s, SHIFT_SHR + hrexw, r0,
>                     TARGET_PAGE_BITS - CPU_TLB_ENTRY_BITS);
>  
> -    tgen_arithi(s, ARITH_AND + rexw, r1,
> +    tgen_arithi(s, ARITH_AND + trexw, r1,
>                  TARGET_PAGE_MASK | ((1 << s_bits) - 1), 0);
> -    tgen_arithi(s, ARITH_AND + rexw, r0,
> +    tgen_arithi(s, ARITH_AND + hrexw, r0,
>                  (CPU_TLB_SIZE - 1) << CPU_TLB_ENTRY_BITS, 0);
>  
> -    tcg_out_modrm_sib_offset(s, OPC_LEA + P_REXW, r0, TCG_AREG0, r0, 0,
> +    tcg_out_modrm_sib_offset(s, OPC_LEA + hrexw, r0, TCG_AREG0, r0, 0,
>                               offsetof(CPUArchState, tlb_table[mem_index][0])
>                               + which);
>  
>      /* cmp 0(r0), r1 */
> -    tcg_out_modrm_offset(s, OPC_CMP_GvEv + rexw, r1, r0, 0);
> +    tcg_out_modrm_offset(s, OPC_CMP_GvEv + trexw, r1, r0, 0);
>  
> -    tcg_out_mov(s, type, r1, addrlo);
> +    tcg_out_mov(s, ttype, r1, addrlo);

This one is not fully correct. It should be ttype for the slow path (the
value is used as an argument to the helper function), but htype for the
fast path (the value is used as a host pointer).

Using ttype currently ensures the type is safe, but it might worth
adding a comment in case ttype or htype is changed.
>  
>      /* jne slow_path */
>      tcg_out_opc(s, OPC_JCC_long + JCC_JNE, 0, 0, 0);
> @@ -1107,7 +1114,7 @@ static inline void tcg_out_tlb_load(TCGContext *s, int addrlo_idx,
>      /* TLB Hit.  */
>  
>      /* add addend(r0), r1 */
> -    tcg_out_modrm_offset(s, OPC_ADD_GvEv + P_REXW, r1, r0,
> +    tcg_out_modrm_offset(s, OPC_ADD_GvEv + hrexw, r1, r0,
>                           offsetof(CPUTLBEntry, addend) - which);
>  }
>  #elif defined(__x86_64__) && defined(__linux__)

This patch (trivially) conflicts with commit 'Tidy qemu_ld/st slow path'
which is now applied, so it has to be updated. Otherwise and except the
above comment, it looks fine to me.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net