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From: | Mark Cave-Ayland |
Subject: | Re: [PATCH 0/2] target/ppc: Fix vextu[bhw][lr]x on big endian hosts |
Date: | Wed, 25 Aug 2021 13:55:56 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 |
On 24/08/2021 21:11, matheus.ferst@eldorado.org.br wrote:
From: Matheus Ferst <matheus.ferst@eldorado.org.br> The definition of struct Int128 is currently independent of the host endianness, causing different results when using the member s128 of union ppc_vsr_t in big-endian builds with CONFIG_INT128 or !CONFIG_INT128. The only PPC instructions that seem to be affected by this issue are the "Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified Left/Right-Index." Even on builds with Int128 support, however, their helpers give the wrong result on big-endian hosts. The first patch in this series changes the definition of struct Int128 to allow its use in the ppc_vsr_t union. The second patch fixes the helper definition. Matheus Ferst (2): include/qemu/int128.h: define struct Int128 according to the host endianness target/ppc: fix vextu[bhw][lr]x helpers include/qemu/int128.h | 19 ++++++++++++------- target/ppc/int_helper.c | 38 ++++++++++---------------------------- 2 files changed, 22 insertions(+), 35 deletions(-)
Hi Matheus,Slightly unrelated to this patchset, however I see you've managed to make some good efforts in consolidating the functionality between big-endian and little-endian host systems.
When I first worked on adding host vector support for PPC I noticed there were some further places in target/ppc/int_helper.c that could be improved from accessing ppc_avr_t fields such as u64 directly and instead using the relevant Vsr*() macros.
If you feel suitably motivated, it would be amazing to see more patches to help this further along: basically look in target/ppc/int_helper.c for individual elements such as u64 (and also the VECTOR_FOR_INORDER_I macro) and determine which ones are better replaced by the relevant Vsr*() macro.
ATB, Mark.
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