Re: [Qemu-devel] [PATCH v2 7/9] tcg-ppc64: Define TCG_TARGET_INSN_UNIT_SIZE

[Peter Maydell]

On 1 April 2014 21:53, Richard Henderson <address@hidden> wrote:
> And use tcg pointer differencing functions as appropriate.
>
> Signed-off-by: Richard Henderson <address@hidden>

Few minor nits and queries below.

> ---
>  tcg/ppc64/tcg-target.c | 163 
> ++++++++++++++++++++++++-------------------------
>  tcg/ppc64/tcg-target.h |   1 +
>  2 files changed, 80 insertions(+), 84 deletions(-)
>
> diff --git a/tcg/ppc64/tcg-target.c b/tcg/ppc64/tcg-target.c
> index 06e440f..a199a96 100644
> --- a/tcg/ppc64/tcg-target.c
> +++ b/tcg/ppc64/tcg-target.c
> @@ -31,7 +31,7 @@
>  #define TCG_CT_CONST_ZERO 0x1000
>  #define TCG_CT_CONST_MONE 0x2000
>
> -static uint8_t *tb_ret_addr;
> +static tcg_insn_unit *tb_ret_addr;
>
>  #if TARGET_LONG_BITS == 32
>  #define LD_ADDR LWZ
> @@ -168,61 +168,53 @@ static inline bool in_range_b(tcg_target_long target)
>      return target == sextract64(target, 0, 26);
>  }
>
> -static uint32_t reloc_pc24_val(void *pc, tcg_target_long target)
> +static uint32_t reloc_pc24_val(void *pc, tcg_insn_unit *target)
>  {
> -    tcg_target_long disp;
> -
> -    disp = target - (tcg_target_long)pc;
> +    ptrdiff_t disp = tcg_ptr_byte_diff(target, pc);
>      assert(in_range_b(disp));
> -
>      return disp & 0x3fffffc;
>  }
>
> -static void reloc_pc24(void *pc, tcg_target_long target)
> +static void reloc_pc24(tcg_insn_unit *pc, tcg_insn_unit *target)
>  {
> -    *(uint32_t *)pc = (*(uint32_t *)pc & ~0x3fffffc)
> -        | reloc_pc24_val(pc, target);
> +    *pc = (*pc & ~0x3fffffc) | reloc_pc24_val(pc, target);
>  }
>
> -static uint16_t reloc_pc14_val(void *pc, tcg_target_long target)
> +static uint16_t reloc_pc14_val(void *pc, tcg_insn_unit *target)

Should be tcg_insn_unit *pc like the others I guess?

>  {
> -    tcg_target_long disp;
> -
> -    disp = target - (tcg_target_long)pc;
> -    if (disp != (int16_t) disp) {
> -        tcg_abort();
> -    }
> -
> +    ptrdiff_t disp = tcg_ptr_byte_diff(target, pc);
> +    assert(disp == (int16_t) disp);
>      return disp & 0xfffc;
>  }
>
> -static void reloc_pc14(void *pc, tcg_target_long target)
> +static void reloc_pc14(tcg_insn_unit *pc, tcg_insn_unit *target)
>  {
> -    *(uint32_t *)pc = (*(uint32_t *)pc & ~0xfffc) | reloc_pc14_val(pc, 
> target);
> +    *pc = (*pc & ~0xfffc) | reloc_pc14_val(pc, target);
>  }
>
>  static inline void tcg_out_b_noaddr(TCGContext *s, int insn)
>  {
> -    unsigned retrans = *(uint32_t *)s->code_ptr & 0x3fffffc;
> +    unsigned retrans = *s->code_ptr & 0x3fffffc;
>      tcg_out32(s, insn | retrans);
>  }
>
>  static inline void tcg_out_bc_noaddr(TCGContext *s, int insn)
>  {
> -    unsigned retrans = *(uint32_t *)s->code_ptr & 0xfffc;
> +    unsigned retrans = *s->code_ptr & 0xfffc;
>      tcg_out32(s, insn | retrans);
>  }
>
> -static void patch_reloc(uint8_t *code_ptr, int type,
> +static void patch_reloc(tcg_insn_unit *code_ptr, int type,
>                          intptr_t value, intptr_t addend)
>  {
> -    value += addend;
> +    /* Note that we always use 0 for addend in calls to tcg_out_reloc.  */

Is this comment saying "assert(addend == 0)" ?

> +    tcg_insn_unit *target = (tcg_insn_unit *)value;
>      switch (type) {
>      case R_PPC_REL14:
> -        reloc_pc14(code_ptr, value);
> +        reloc_pc14(code_ptr, target);
>          break;
>      case R_PPC_REL24:
> -        reloc_pc24(code_ptr, value);
> +        reloc_pc24(code_ptr, target);
>          break;
>      default:
>          tcg_abort();

> @@ -836,7 +832,7 @@ static const uint32_t qemu_exts_opc[4] = {
>  /* helper signature: helper_ld_mmu(CPUState *env, target_ulong addr,
>   *                                 int mmu_idx, uintptr_t ra)
>   */
> -static const void * const qemu_ld_helpers[16] = {
> +static void * const qemu_ld_helpers[16] = {
>      [MO_UB]   = helper_ret_ldub_mmu,
>      [MO_LEUW] = helper_le_lduw_mmu,
>      [MO_LEUL] = helper_le_ldul_mmu,
> @@ -849,7 +845,7 @@ static const void * const qemu_ld_helpers[16] = {
>  /* helper signature: helper_st_mmu(CPUState *env, target_ulong addr,
>   *                                 uintxx_t val, int mmu_idx, uintptr_t ra)
>   */
> -static const void * const qemu_st_helpers[16] = {
> +static void * const qemu_st_helpers[16] = {

Why do we lose the extra 'const' here?

> @@ -1115,7 +1111,8 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>  #ifndef __APPLE__
>      /* First emit adhoc function descriptor */
>      tcg_out64(s, (uint64_t)s->code_ptr + 24); /* entry point */
> -    s->code_ptr += 16;          /* skip TOC and environment pointer */
> +    tcg_out64(s, 0);                          /* toc */
> +    tcg_out64(s, 0);                          /* environment pointer */

This is a behaviour change, right? Is it a bugfix or just a "doesn't
matter if we write zeros here or not" thing?

thanks
-- PMM