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From: | Richard Henderson |
Subject: | Re: [Qemu-ppc] [Qemu-devel] [RFC v1 09/13] target-ppc: add cmpeqb instruction |
Date: | Thu, 21 Jul 2016 12:11:56 +0530 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 |
On 07/18/2016 10:35 PM, Nikunj A Dadhania wrote:
+ tcg_gen_andi_tl(src1, cpu_gpr[rA(ctx->opcode)], 0xFF); + for (i = 0; i < 64; i += 8) { + tcg_gen_shri_tl(t0, arg1, i); + tcg_gen_andi_tl(t0, t0, 0xFF); + tcg_gen_brcond_tl(TCG_COND_EQ, src1, t0, l1); + } + tcg_gen_movi_i32(cpu_crf[crfD(ctx->opcode)], 0); + tcg_gen_br(l2); + gen_set_label(l1); + /* Set match bit, i.e. CRF_GT */ + tcg_gen_movi_i32(cpu_crf[crfD(ctx->opcode)], 1 << CRF_GT);
Ew. This can be done much better as http://graphics.stanford.edu/~seander/bithacks.html#ZeroInWordWhich still might be best done in a helper, because of the constants involved (tcg is not nearly so good as gcc in building full 64-bit constants).
C.f. target-alpha/int_helper.c, helper_cmpbe0 (which computes different information than cmpeqb, but is still helpful as an example).
r~
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