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Re: [Qemu-devel] [PATCH 1/1] tcg/aarch64: Implement tlb lookup fast path
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 1/1] tcg/aarch64: Implement tlb lookup fast path |
Date: |
Thu, 20 Jun 2013 09:55:59 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 |
On 06/20/2013 07:58 AM, Claudio Fontana wrote:
>> > + tcg_out_ldst(s, TARGET_LONG_BITS == 64 ? LDST_64 : LDST_32,
>> > + LDST_LD, TCG_REG_X0, TCG_REG_X2, tlb_offset & 0xfff);
>> > + tcg_out_ldst(s, LDST_64, LDST_LD, TCG_REG_X1, TCG_REG_X2,
>> > + (tlb_offset & 0xfff) + (offsetof(CPUTLBEntry, addend) -
>> > + (is_read ? offsetof(CPUTLBEntry, addr_read) :
>> > + offsetof(CPUTLBEntry, addr_write))));
>> > +
>> > + tcg_out_cmp(s, 1, TCG_REG_X0, TCG_REG_X3, 0);
>> > + *label_ptr = s->code_ptr;
>> > + tcg_out_goto_cond_noaddr(s, TCG_COND_NE);
>> > +}
> hmm should not the compare and branch actually be before the loading of the
> addend?
> If we jump to the slow path we don't need to load the addend do we?
>
No, but it's the slow path, and we don't care if we do extra work.
What's more important is minimizing the memory load delay for the
fast path.
r~