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Re: [Qemu-devel] Shifts, ppc[64], xtensa
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] Shifts, ppc[64], xtensa |
Date: |
Wed, 19 Sep 2012 10:00:38 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 |
On 09/19/2012 05:57 AM, Peter Maydell wrote:
>> > - s->code_ptr += 16;
>> > + tcg_out32 (s, NOP);
>> > + tcg_out32 (s, NOP);
>> > + tcg_out32 (s, NOP);
>> > + tcg_out32 (s, NOP);
> Not too familiar with the PPC backend, but doesn't this mean that
> in the retranslation case we will overwrite a correct jump destination
> with these NOP words and then rewrite it again with the correct
> destination? That can cause problems with cache incoherency;
> compare the fix applied in commit c69806ab8276 for ARM.
Well, i386 certainly doesn't care about re-translation here:
/* direct jump method */
tcg_out8(s, OPC_JMP_long); /* jmp im */
s->tb_jmp_offset[args[0]] = s->code_ptr - s->code_buf;
tcg_out32(s, 0);
That creates an explicit branch to next.
And as far as the referenced change, that has to do with "real"
branches, i.e. INDEX_op_brcond et at. Which *do* need to be
protected against retranslation. But INDEX_op_goto_tb is a
different case.
r~
- [Qemu-devel] Shifts, ppc[64], xtensa, malc, 2012/09/18
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Max Filippov, 2012/09/18
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/18
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa,
Richard Henderson <=
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Aurelien Jarno, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19