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Re: [Qemu-devel] [PATCH 14/60] AArch64: Add orr instruction emulation
From: |
Claudio Fontana |
Subject: |
Re: [Qemu-devel] [PATCH 14/60] AArch64: Add orr instruction emulation |
Date: |
Mon, 18 Nov 2013 11:15:09 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120909 Thunderbird/15.0.1 |
Hello,
On 09/27/2013 08:25 PM, Richard Henderson wrote:
> On 09/26/2013 05:48 PM, Alexander Graf wrote:
>> This patch adds emulation support for the orr instruction.
>>
>> Signed-off-by: Alexander Graf <address@hidden>
>> ---
>> target-arm/helper-a64.c | 28 +++++++++++
>> target-arm/helper-a64.h | 1 +
>> target-arm/translate-a64.c | 120
>> +++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 149 insertions(+)
>>
>> diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
>> index 8105fb5..da72b7f 100644
>> --- a/target-arm/helper-a64.c
>> +++ b/target-arm/helper-a64.c
>> @@ -24,3 +24,31 @@
>> #include "sysemu/sysemu.h"
>> #include "qemu/bitops.h"
>>
>> +uint32_t HELPER(pstate_add)(uint32_t pstate, uint64_t a1, uint64_t a2,
>> + uint64_t ar)
>> +{
>> + int64_t s1 = a1;
>> + int64_t s2 = a2;
>> + int64_t sr = ar;
>> +
>> + pstate &= ~(PSTATE_N | PSTATE_Z | PSTATE_C | PSTATE_V);
>> +
>> + if (sr < 0) {
>> + pstate |= PSTATE_N;
>> + }
>> +
>> + if (!ar) {
>> + pstate |= PSTATE_Z;
>> + }
>> +
>> + if (ar && (ar < a1)) {
>> + pstate |= PSTATE_C;
>> + }
>> +
>> + if ((s1 > 0 && s2 > 0 && sr < 0) ||
>> + (s1 < 0 && s2 < 0 && sr > 0)) {
>> + pstate |= PSTATE_V;
>> + }
>> +
>> + return pstate;
>> +}
>
> Why are you not using the same split apart bits as A32?
>
>> + /* XXX carry_out */
>> + switch (shift_type) {
>
> What carry out? I see no such in the ShiftReg description.
>
>> + case 3:
>> + tcg_gen_rotr_i64(r, cpu_reg(reg), tcg_shift);
>> + break;
>
> Incorrect rotate for 32bit?
>
>> +static void handle_orr(DisasContext *s, uint32_t insn)
>> +{
>> + int is_32bit = !get_bits(insn, 31, 1);
>> + int dest = get_reg(insn);
>> + int source = get_bits(insn, 5, 5);
>> + int rm = get_bits(insn, 16, 5);
>> + int shift_amount = get_sbits(insn, 10, 6);
>> + int is_n = get_bits(insn, 21, 1);
>> + int shift_type = get_bits(insn, 22, 2);
>> + int opc = get_bits(insn, 29, 2);
>> + bool setflags = (opc == 0x3);
>> + TCGv_i64 tcg_op2;
>> + TCGv_i64 tcg_dest;
>> +
>> + if (is_32bit && (shift_amount < 0)) {
>> + /* reserved value */
>> + unallocated_encoding(s);
>> + }
>
> Why are you extracting shift_amount signed?
>
>> +
>> + /* MOV is dest = xzr & (source & ~0) */
>
> Comment is wrong.
>
>> + if (!shift_amount && source == 0x1f) {
Besides the comment, is this correct?
I am trying to rework this patch, but this part seems incorrect to me.
We land here for the AND as well, and if source(rn) is xzr,
then I would expect the result to be zero for AND regardless of anything else,
and not a MOV.
Can we really do this optimization in general here for AND, OR, EOR?
Thanks for any clarification,
Claudio
>> + if (is_32bit) {
>> + tcg_gen_ext32u_i64(cpu_reg_sp(dest), cpu_reg(rm));
>> + } else {
>> + tcg_gen_mov_i64(cpu_reg_sp(dest), cpu_reg(rm));
>> + }
>> + if (is_n) {
>> + tcg_gen_not_i64(cpu_reg_sp(dest), cpu_reg_sp(dest));
>> + }
>> + if (is_32bit) {
>> + tcg_gen_ext32u_i64(cpu_reg_sp(dest), cpu_reg_sp(dest));
>> + }
>
> These are incorrect -- no sp in the logical ops, but xzr instead.
>
> And surely we can emit fewer opcodes for the simple cases here.
> Since these are the canonical aliases for mov/mvn, it'll pay off.
>
> TCGv src = cpu_reg(rm);
> TCGv dst = cpu_reg(rd);
>
> if (is_n) {
> tcg_gen_not_i64(dst, src);
> src = dst;
> }
> if (is_32bit) {
> tcg_gen_ext32u_i64(dst, src);
> } else {
> tcg_gen_mov_i64(dst, src);
> }
>
> Note that tcg_gen_mov_i64 does the src == dst check, so a simple
> 64-bit mvn will only emit the not.
>
>
>> + tcg_dest = cpu_reg(dest);
>> + switch (opc) {
>> + case 0x0:
>> + case 0x3:
>> + tcg_gen_and_i64(tcg_dest, cpu_reg(source), tcg_op2);
>> + break;
>> + case 0x1:
>> + tcg_gen_or_i64(tcg_dest, cpu_reg(source), tcg_op2);
>> + break;
>> + case 0x2:
>> + tcg_gen_xor_i64(tcg_dest, cpu_reg(source), tcg_op2);
>> + break;
>> + }
>> +
>> + if (is_32bit) {
>> + tcg_gen_ext32u_i64(tcg_dest, tcg_dest);
>> + }
>> +
>> + if (setflags) {
>> + gen_helper_pstate_add(pstate, pstate, tcg_dest, cpu_reg(31),
>> tcg_dest);
>> + }
>
> Incorrect flags generated. They're different between add/sub and logical.
> In particular, C and V are always zero.
>
>> + handle_orr(s, insn);
>
> And please use a more proper name than ORR for something that handles all
> of the logical insns.
>
>
> r~
>
- Re: [Qemu-devel] [PATCH 14/60] AArch64: Add orr instruction emulation,
Claudio Fontana <=