Re: [Qemu-devel] [PATCH 05/20] tcg-ia64: Move AREG0 to R32

[Aurelien Jarno <aurelien@aurel32.net>]

On Thu, Oct 31, 2013 at 01:21:54PM -0700, Richard Henderson wrote:
> Since the move away from the global areg0, we're no longer globally
> reserving areg0.  Which means our use of R7 clobbers a call-saved
> register.  Shift areg0 into the windowed registers.  Indeed, choose
> the incoming parameter register that it comes to us by.
> 
> This requires moving the register holding the return address elsewhere.
> Choose R33 for tidiness.
> 
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/ia64/tcg-target.c | 13 ++++++-------
>  tcg/ia64/tcg-target.h |  4 ++--
>  2 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/tcg/ia64/tcg-target.c b/tcg/ia64/tcg-target.c
> index 2fdc38a5..336781f 100644
> --- a/tcg/ia64/tcg-target.c
> +++ b/tcg/ia64/tcg-target.c
> @@ -109,7 +109,6 @@ enum {
>  };
>  
>  static const int tcg_target_reg_alloc_order[] = {
> -    TCG_REG_R33,
>      TCG_REG_R35,
>      TCG_REG_R36,
>      TCG_REG_R37,
> @@ -2404,8 +2403,7 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>      tcg_out_bundle(s, miI,
>                     tcg_opc_m34(TCG_REG_P0, OPC_ALLOC_M34,
>                                 TCG_REG_R34, 32, 24, 0),
> -                   tcg_opc_a4 (TCG_REG_P0, OPC_ADDS_A4,
> -                               TCG_AREG0, 0, TCG_REG_R32),
> +                   INSN_NOP_I,
>                     tcg_opc_i21(TCG_REG_P0, OPC_MOV_I21,
>                                 TCG_REG_B6, TCG_REG_R33, 0));
>  
> @@ -2424,7 +2422,7 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>                     tcg_opc_a4 (TCG_REG_P0, OPC_ADDS_A4,
>                                 TCG_REG_R12, -frame_size, TCG_REG_R12),
>                     tcg_opc_i22(TCG_REG_P0, OPC_MOV_I22,
> -                               TCG_REG_R32, TCG_REG_B0),
> +                               TCG_REG_R33, TCG_REG_B0),
>                     tcg_opc_b4 (TCG_REG_P0, OPC_BR_SPTK_MANY_B4, TCG_REG_B6));
>  
>      /* epilogue */
> @@ -2432,7 +2430,7 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>      tcg_out_bundle(s, miI,
>                     INSN_NOP_M,
>                     tcg_opc_i21(TCG_REG_P0, OPC_MOV_I21,
> -                               TCG_REG_B0, TCG_REG_R32, 0),
> +                               TCG_REG_B0, TCG_REG_R33, 0),
>                     tcg_opc_a4 (TCG_REG_P0, OPC_ADDS_A4,
>                                 TCG_REG_R12, frame_size, TCG_REG_R12));
>      tcg_out_bundle(s, miB,
> @@ -2489,16 +2487,17 @@ static void tcg_target_init(TCGContext *s)
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R3);   /* internal use */
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R12);  /* stack pointer */
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R13);  /* thread pointer */
> -    tcg_regset_set_reg(s->reserved_regs, TCG_REG_R32);  /* return address */
> +    tcg_regset_set_reg(s->reserved_regs, TCG_REG_R33);  /* return address */
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R34);  /* PFS */
>  
> -    /* The following 3 are not in use, are call-saved, but *not* saved
> +    /* The following 4 are not in use, are call-saved, but *not* saved
>         by the prologue.  Therefore we cannot use them without modifying
>         the prologue.  There doesn't seem to be any good reason to use
>         these as opposed to the windowed registers.  */
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R4);
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R5);
>      tcg_regset_set_reg(s->reserved_regs, TCG_REG_R6);
> +    tcg_regset_set_reg(s->reserved_regs, TCG_REG_R7);
>  
>      tcg_add_target_add_op_defs(ia64_op_defs);
>  }
> diff --git a/tcg/ia64/tcg-target.h b/tcg/ia64/tcg-target.h
> index c90038a..52a939c 100644
> --- a/tcg/ia64/tcg-target.h
> +++ b/tcg/ia64/tcg-target.h
> @@ -92,6 +92,8 @@ typedef enum {
>      TCG_REG_R61,
>      TCG_REG_R62,
>      TCG_REG_R63,
> +
> +    TCG_AREG0 = TCG_REG_R32,
>  } TCGReg;
>  
>  #define TCG_CT_CONST_ZERO 0x100
> @@ -162,8 +164,6 @@ typedef enum {
>  #define TCG_TARGET_HAS_not_i32          0 /* xor r1, -1, r3 */
>  #define TCG_TARGET_HAS_not_i64          0 /* xor r1, -1, r3 */
>  
> -#define TCG_AREG0 TCG_REG_R7
> -
>  static inline void flush_icache_range(uintptr_t start, uintptr_t stop)
>  {
>      start = start & ~(32UL - 1UL);

Acked-by: Aurelien Jarno <aurelien@aurel32.net>

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