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Re: [Qemu-devel] [PATCH 2/2] s390x: Add laa and laag instructions
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] s390x: Add laa and laag instructions |
Date: |
Mon, 11 May 2015 20:53:56 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 |
On 05/07/2015 06:12 PM, Alexander Graf wrote:
> +static ExitStatus op_laa(DisasContext *s, DisasOps *o)
> +{
> + TCGv_i64 m2 = tcg_temp_new_i64();
> +
> + /* XXX should be atomic */
> + tcg_gen_qemu_ld32s(m2, o->in2, get_mem_index(s));
> +
> + /* Set r1 to the unmodified contents of m2 */
> + tcg_gen_mov_i64(o->out, m2);
> +
> + /* m2 = r3 + m2 */
> + tcg_gen_add_i64(m2, o->in1, m2);
> + tcg_gen_qemu_st32(m2, o->in2, get_mem_index(s));
> +
> + /* Set in2 to the input operand for cc calculation */
> + tcg_gen_mov_i64(o->in2, o->out);
> +
> + tcg_temp_free_i64(m2);
> + return NO_EXIT;
> +}
I don't believe that this computes the right cc.
You need to place m2 into in2, not out.
That said, maybe
tcg_temp_free_i64(o->in2);
o->in2 = m2;
is the right way to perform that copy. Since we
know that in2 was in2_a2, allocating a temp for an
address, we also know we can both (1) free it and
(2) put another temp in there that will be freed.
Don't worry about the atomic-ness of the operation
until some of the many patch sets going round on
that very subject are resolved. This will be good
enough for system mode for now.
I think maybe the whole target ought to be cleaned
up for the new TCGMemOps. For this, you could share
the code for LAA and LAAG with the TCGMemOp in insn->data.
r~