From: Richard Henderson <richard.henderson@linaro.org>
To: matheus.ferst@eldorado.org.br, qemu-devel@nongnu.org,
qemu-ppc@nongnu.org
Cc: lagarcia@br.ibm.com, bruno.larsen@eldorado.org.br,
luis.pires@eldorado.org.br, f4bug@amsat.org,
david@gibson.dropbear.id.au
Subject: Re: [PATCH v4 29/31] target/ppc: Implement cfuged instruction
Date: Thu, 13 May 2021 06:31:27 -0500 [thread overview]
Message-ID: <49b2a677-a3cc-b944-dd4d-edd115c81039@linaro.org> (raw)
In-Reply-To: <20210512185441.3619828-30-matheus.ferst@eldorado.org.br>
On 5/12/21 1:54 PM, matheus.ferst@eldorado.org.br wrote:
> + while (i) {
> + n = ctz64(mask);
> + if (n > i) {
> + n = i;
> + }
> +
> + m = (1ll << n) - 1;
> + if (bit) {
> + right = ror64(right | (src & m), n);
> + } else {
> + left = ror64(left | (src & m), n);
> + }
> +
> + src >>= n;
> + mask >>= n;
> + i -= n;
> + bit = !bit;
> + mask = ~mask;
> + }
> +
> + if (bit) {
> + n = ctpop64(mask);
> + } else {
> + n = 64 - ctpop64(mask);
> + }
> +
> + return left | (right >> n);
> +}
This doesn't correspond to the algorithm presented in the manual. Thus this
requires lots of extra commentary.
I guess I see how you're trying to process blocks at a time, instead of single
bits at a time. But I don't think the merging of data into "right" and "left"
looks right. I would have expected
right = (right << n) | (src & m);
and similarly for left.
It doesn't look like that the ctpop at the end is correct, given how mask has
been modified. I would have thought that
n = ctpop64(orig_mask);
return (left << n) | right;
would be the correct answer.
I could be wrong about the above, but that's what the missing commentary should
have helped me understand.
> +static bool trans_CFUGED(DisasContext *ctx, arg_X *a)
> +{
> + REQUIRE_64BIT(ctx);
> + REQUIRE_INSNS_FLAGS2(ctx, ISA310);
> +#if defined(TARGET_PPC64)
> + gen_helper_cfuged(cpu_gpr[a->ra], cpu_gpr[a->rt], cpu_gpr[a->rb]);
> +#else
> + gen_invalid(ctx);
> +#endif
> + return true;
> +}
Given that this helper will also be used by vcfuged, there's no point in hiding
it in a TARGET_PPC64 block, and thus you can drop the ifdefs.
r~
next prev parent reply other threads:[~2021-05-13 11:32 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 18:54 [PATCH v4 00/31] Base for adding PowerPC 64-bit instructions matheus.ferst
2021-05-12 18:54 ` [PATCH v4 01/31] target/ppc: Add cia field to DisasContext matheus.ferst
2021-05-13 4:03 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 02/31] target/ppc: Split out decode_legacy matheus.ferst
2021-05-13 4:03 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 03/31] target/ppc: Move DISAS_NORETURN setting into gen_exception* matheus.ferst
2021-05-13 4:06 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 04/31] target/ppc: Remove special case for POWERPC_SYSCALL matheus.ferst
2021-05-13 4:06 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 05/31] target/ppc: Remove special case for POWERPC_EXCP_TRAP matheus.ferst
2021-05-13 4:07 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 06/31] target/ppc: Simplify gen_debug_exception matheus.ferst
2021-05-13 4:08 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 07/31] target/ppc: Introduce DISAS_{EXIT,CHAIN}{,_UPDATE} matheus.ferst
2021-05-13 4:10 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 08/31] target/ppc: Replace POWERPC_EXCP_SYNC with DISAS_EXIT matheus.ferst
2021-05-12 19:31 ` Bruno Piazera Larsen
2021-05-13 4:11 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 09/31] target/ppc: Remove unnecessary gen_io_end calls matheus.ferst
2021-05-13 4:12 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 10/31] target/ppc: Introduce gen_icount_io_start matheus.ferst
2021-05-12 19:21 ` Matheus K. Ferst
2021-05-13 4:14 ` David Gibson
2021-05-12 18:54 ` [PATCH v4 11/31] target/ppc: Replace POWERPC_EXCP_STOP with DISAS_EXIT_UPDATE matheus.ferst
2021-05-12 18:54 ` [PATCH v4 12/31] target/ppc: Replace POWERPC_EXCP_BRANCH with DISAS_NORETURN matheus.ferst
2021-05-12 18:54 ` [PATCH v4 13/31] target/ppc: Remove DisasContext.exception matheus.ferst
2021-05-12 18:54 ` [PATCH v4 14/31] target/ppc: Move single-step check to ppc_tr_tb_stop matheus.ferst
2021-05-12 18:54 ` [PATCH v4 15/31] target/ppc: Tidy exception vs exit_tb matheus.ferst
2021-05-12 18:54 ` [PATCH v4 16/31] target/ppc: Mark helper_raise_exception* as noreturn matheus.ferst
2021-05-12 18:54 ` [PATCH v4 17/31] target/ppc: Use translator_loop_temp_check matheus.ferst
2021-05-12 19:45 ` Bruno Piazera Larsen
2021-05-12 18:54 ` [PATCH v4 18/31] target/ppc: Introduce macros to check isa extensions matheus.ferst
2021-05-12 18:54 ` [PATCH v4 19/31] target/ppc: Move page crossing check to ppc_tr_translate_insn matheus.ferst
2021-05-12 18:54 ` [PATCH v4 20/31] target/ppc: Add infrastructure for prefixed insns matheus.ferst
2021-05-12 18:54 ` [PATCH v4 21/31] target/ppc: Move ADDI, ADDIS to decodetree, implement PADDI matheus.ferst
2021-05-12 18:54 ` [PATCH v4 22/31] target/ppc: Implement PNOP matheus.ferst
2021-05-13 10:37 ` Richard Henderson
2021-05-12 18:54 ` [PATCH v4 23/31] TCG: add tcg_constant_tl matheus.ferst
2021-05-13 10:42 ` Richard Henderson
2021-05-12 18:54 ` [PATCH v4 24/31] target/ppc: Move D/DS/X-form integer loads to decodetree matheus.ferst
2021-05-12 18:54 ` [PATCH v4 25/31] target/ppc: Implement prefixed integer load instructions matheus.ferst
2021-05-13 10:50 ` Richard Henderson
2021-05-12 18:54 ` [PATCH v4 26/31] target/ppc: Move D/DS/X-form integer stores to decodetree matheus.ferst
2021-05-12 18:54 ` [PATCH v4 27/31] target/ppc: Implement prefixed integer store instructions matheus.ferst
2021-05-12 18:54 ` [PATCH v4 28/31] target/ppc: Implement setbc/setbcr/stnbc/setnbcr instructions matheus.ferst
2021-05-13 11:01 ` Richard Henderson
2021-05-13 11:43 ` Matheus K. Ferst
2021-05-12 18:54 ` [PATCH v4 29/31] target/ppc: Implement cfuged instruction matheus.ferst
2021-05-13 11:31 ` Richard Henderson [this message]
2021-05-13 12:24 ` Matheus K. Ferst
2021-05-14 0:01 ` Richard Henderson
2021-05-12 18:54 ` [PATCH v4 30/31] target/ppc: Implement vcfuged instruction matheus.ferst
2021-05-13 11:36 ` Richard Henderson
2021-05-12 18:54 ` [PATCH v4 31/31] target/ppc: Move addpcis to decodetree matheus.ferst
2021-05-13 11:40 ` Richard Henderson
2021-05-13 4:22 ` [PATCH v4 00/31] Base for adding PowerPC 64-bit instructions David Gibson
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