On Tue, Aug 8, 2023 at 1:02 PM Richard Henderson
<richard.hender...@linaro.org> wrote:
>
> When a direct branch is out of range, we can load the destination for
> the indirect branch using PLA (for 16GB worth of buffer) and PLD from
> the TranslationBlock for everything larger.
>
> This means the patch affects exactly one instruction: B (plus filler),
> PLA or PLD. Which means we can update and execute the patch atomically.
I think the commit message needs to be updated for Nick's changes.
>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> tcg/ppc/tcg-target.c.inc | 31 +++++++++++++++++++------------
> 1 file changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/tcg/ppc/tcg-target.c.inc b/tcg/ppc/tcg-target.c.inc
> index 63fe4ef995..b686a68247 100644
> --- a/tcg/ppc/tcg-target.c.inc
> +++ b/tcg/ppc/tcg-target.c.inc
> @@ -2646,31 +2646,38 @@ static void tcg_out_goto_tb(TCGContext *s, int which)
> uintptr_t ptr = get_jmp_target_addr(s, which);
>
> if (USE_REG_TB) {
> + /*
> + * With REG_TB, we must always use indirect branching,
> + * so that the branch destination and TCG_REG_TB match.
> + */
> ptrdiff_t offset = tcg_tbrel_diff(s, (void *)ptr);
> tcg_out_mem_long(s, LD, LDX, TCG_REG_TB, TCG_REG_TB, offset);
> -
> - /* TODO: Use direct branches when possible. */
> - set_jmp_insn_offset(s, which);
> tcg_out32(s, MTSPR | RS(TCG_REG_TB) | CTR);
> -
> tcg_out32(s, BCCTR | BO_ALWAYS);
>
> /* For the unlinked case, need to reset TCG_REG_TB. */
> set_jmp_reset_offset(s, which);
> tcg_out_mem_long(s, ADDI, ADD, TCG_REG_TB, TCG_REG_TB,
> -tcg_current_code_size(s));
> - } else {
> - /* Direct branch will be patched by tb_target_set_jmp_target. */
> - set_jmp_insn_offset(s, which);
> - tcg_out32(s, NOP);
> + return;
> + }
>
> - /* When branch is out of range, fall through to indirect. */
> + /* Direct branch will be patched by tb_target_set_jmp_target. */
> + set_jmp_insn_offset(s, which);
> + tcg_out32(s, NOP);
> +
> + /* When branch is out of range, fall through to indirect. */
> + if (have_isa_3_10) {
> + ptrdiff_t offset = tcg_pcrel_diff_for_prefix(s, (void *)ptr);
> + tcg_out_8ls_d(s, PLD, TCG_REG_TMP1, 0, offset, 1);
> + } else {
> tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_TMP1, ptr - (int16_t)ptr);
> tcg_out_ld(s, TCG_TYPE_PTR, TCG_REG_TMP1, TCG_REG_TMP1,
> (int16_t)ptr);
> - tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR);
> - tcg_out32(s, BCCTR | BO_ALWAYS);
> - set_jmp_reset_offset(s, which);
> }
> +
> + tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR);
> + tcg_out32(s, BCCTR | BO_ALWAYS);
> + set_jmp_reset_offset(s, which);
> }
>
> void tb_target_set_jmp_target(const TranslationBlock *tb, int n,
> --
> 2.34.1
>
Thank you for implementing this Richard.
I was able to boot mttcg guests on P9 and P10 hosts.
Tested-by: Jordan Niethe <jniet...@gmail.com>
Reviewed-by: Jordan Niethe <jniet...@gmail.com>
