From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-s390x <qemu-s390x@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [PATCH v3 13/29] tcg/s390: Support bswap flags
Date: Mon, 28 Jun 2021 07:50:11 -0700 [thread overview]
Message-ID: <d2e66cdd-6fab-d898-b18a-f0c18709c912@linaro.org> (raw)
In-Reply-To: <CAFEAcA_HiW05hA0wC-DGNSpnH-L7p_cj6ZFvAWpA0GQBcZvMVQ@mail.gmail.com>
On 6/28/21 7:43 AM, Peter Maydell wrote:
> On Sat, 26 Jun 2021 at 07:44, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> For INDEX_op_bswap16_i64, use 64-bit instructions so that we can
>> easily provide the extension to 64-bits. Drop the special case,
>> previously used, where the input is already zero-extended -- the
>> minor code size savings is not worth the complication.
>>
>> Cc: qemu-s390x@nongnu.org
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>
>> + case INDEX_op_bswap32_i32:
>> tcg_out_insn(s, RRE, LRVR, args[0], args[1]);
>> break;
>
> When we're working with i32s, is the top half of the host register
> zero or garbage ?
The general case on s390x is that the top half of the host register is unmodified by insns
with 32-bit operands. This is true for LRVR.
It's also true for LRVRH, with its 16-bit operand. Which is why it's not as useful as it
could be.
r~
next prev parent reply other threads:[~2021-06-28 14:51 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-26 6:36 [PATCH v3 00/29] tcg: bswap improvements Richard Henderson
2021-06-26 6:36 ` [PATCH v3 01/29] tcg: Add flags argument to bswap opcodes Richard Henderson
2021-06-26 6:36 ` [PATCH v3 02/29] tcg/i386: Support bswap flags Richard Henderson
2021-06-26 6:36 ` [PATCH v3 03/29] tcg/aarch64: Merge tcg_out_rev{16,32,64} Richard Henderson
2021-06-28 14:16 ` Peter Maydell
2021-06-26 6:36 ` [PATCH v3 04/29] tcg/aarch64: Support bswap flags Richard Henderson
2021-06-26 9:38 ` Philippe Mathieu-Daudé
2021-06-26 6:36 ` [PATCH v3 05/29] tcg/arm: " Richard Henderson
2021-06-26 6:36 ` [PATCH v3 06/29] tcg/ppc: Split out tcg_out_ext{8,16,32}s Richard Henderson
2021-06-26 6:36 ` [PATCH v3 07/29] tcg/ppc: Split out tcg_out_sari{32,64} Richard Henderson
2021-06-26 6:36 ` [PATCH v3 08/29] tcg/ppc: Split out tcg_out_bswap16 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 09/29] tcg/ppc: Split out tcg_out_bswap32 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 10/29] tcg/ppc: Split out tcg_out_bswap64 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 11/29] tcg/ppc: Support bswap flags Richard Henderson
2021-06-26 9:32 ` Philippe Mathieu-Daudé
2021-06-26 6:36 ` [PATCH v3 12/29] tcg/ppc: Use power10 byte-reverse instructions Richard Henderson
2021-06-28 14:33 ` Peter Maydell
2021-06-28 14:45 ` Richard Henderson
2021-06-28 16:22 ` Bruno Piazera Larsen
2021-06-26 6:36 ` [PATCH v3 13/29] tcg/s390: Support bswap flags Richard Henderson
2021-06-28 14:43 ` Peter Maydell
2021-06-28 14:50 ` Richard Henderson [this message]
2021-06-26 6:36 ` [PATCH v3 14/29] tcg/mips: Support bswap flags in tcg_out_bswap16 Richard Henderson
2021-06-26 9:30 ` Philippe Mathieu-Daudé
2021-06-26 6:36 ` [PATCH v3 15/29] tcg/mips: Support bswap flags in tcg_out_bswap32 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 16/29] tcg/tci: Support bswap flags Richard Henderson
2021-06-26 6:36 ` [PATCH v3 17/29] tcg: Handle new bswap flags during optimize Richard Henderson
2021-06-26 6:36 ` [PATCH v3 18/29] tcg: Add flags argument to tcg_gen_bswap16_*, tcg_gen_bswap32_i64 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 19/29] tcg: Make use of bswap flags in tcg_gen_qemu_ld_* Richard Henderson
2021-06-26 6:36 ` [PATCH v3 20/29] tcg: Make use of bswap flags in tcg_gen_qemu_st_* Richard Henderson
2021-06-26 6:36 ` [PATCH v3 21/29] target/arm: Improve REV32 Richard Henderson
2021-06-26 6:36 ` [PATCH v3 22/29] target/arm: Improve vector REV Richard Henderson
2021-06-26 6:36 ` [PATCH v3 23/29] target/arm: Improve REVSH Richard Henderson
2021-06-26 6:36 ` [PATCH v3 24/29] target/i386: Improve bswap translation Richard Henderson
2021-06-26 6:36 ` [PATCH v3 25/29] target/sh4: Improve swap.b translation Richard Henderson
2021-06-26 6:36 ` [PATCH v3 26/29] target/mips: Fix gen_mxu_s32ldd_s32lddr Richard Henderson
2021-06-26 6:36 ` [PATCH v3 27/29] tcg/arm: Unset TCG_TARGET_HAS_MEMORY_BSWAP Richard Henderson
2021-06-26 6:36 ` [PATCH v3 28/29] tcg/aarch64: " Richard Henderson
2021-06-26 6:36 ` [PATCH v3 29/29] tcg/riscv: Remove MO_BSWAP handling Richard Henderson
2021-06-26 7:03 ` [PATCH v3 00/29] tcg: bswap improvements no-reply
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