[Tarantool-patches] [PATCH luajit v2] x64: Fix 64 bit shift code generation.
Sergey Kaplun
skaplun at tarantool.org
Wed Jun 28 13:57:48 MSK 2023
Hi, Maxim!
Thanks for the fixes!
LGTM, with an ignorable nit below.
Also, I suppose it is better to rebase on the newest master (since
merged C tests may conflict with your changes).
On 13.06.23, Maxim Kokryashkin wrote:
> From: Mike Pall <mike>
>
> Reported by Philipp Kutin.
> Fix contributed by Peter Cawley.
>
> (cherry-picked from commit 03a7ebca4f6819658cdaa12ba3af54a17b8035e9)
<snipped>
>
> Branch: https://github.com/tarantool/luajit/tree/fckxorg/fix-bit-shift-generation
> PR: https://github.com/tarantool/tarantool/pull/8727
>
> src/lj_asm_x86.h | 2 +-
> test/tarantool-tests/CMakeLists.txt | 1 +
> .../fix-bit-shift-generation.test.lua | 48 +++++++++++++++++++
> .../fix-bit-shift-generation/CMakeLists.txt | 1 +
> .../libtestbitshift.c | 8 ++++
> 5 files changed, 59 insertions(+), 1 deletion(-)
> create mode 100644 test/tarantool-tests/fix-bit-shift-generation.test.lua
> create mode 100644 test/tarantool-tests/fix-bit-shift-generation/CMakeLists.txt
> create mode 100644 test/tarantool-tests/fix-bit-shift-generation/libtestbitshift.c
>
> diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
> index e6c42c6d..63d332ca 100644
> --- a/src/lj_asm_x86.h
> +++ b/src/lj_asm_x86.h
<snipped>
> diff --git a/test/tarantool-tests/CMakeLists.txt b/test/tarantool-tests/CMakeLists.txt
> index a428d009..d36271f1 100644
> --- a/test/tarantool-tests/CMakeLists.txt
> +++ b/test/tarantool-tests/CMakeLists.txt
<snipped>
> diff --git a/test/tarantool-tests/fix-bit-shift-generation.test.lua b/test/tarantool-tests/fix-bit-shift-generation.test.lua
> new file mode 100644
> index 00000000..e3f30eae
> --- /dev/null
> +++ b/test/tarantool-tests/fix-bit-shift-generation.test.lua
<snipped>
> +local testbitshift = ffi.load('testbitshift')
> +ffi.cdef[[
> +uint64_t
> +testbitshift
> +(const int arg1, const int arg2, const int arg3, const uint64_t arg4)
Side note: See the ignorable comment for the testbitshift lib below.
> +]]
> +
> +local result = {}
> +jit.opt.start('hotloop=1')
> +
> +for i = 1, NTESTS do
> + -- The rotation is performed beyond the 32-bit size, for
> + -- truncation to become noticeable. `testbitshift` is used to
> + -- ensure that the result of rotation goes into the `rcx`,
> + -- corresponding to the x86_64 ABI. Although it is possible to
> + -- use a function from the C standard library for that, all of
> + -- the suitable ones are variadic, and variadics are recorded
> + -- incorrectly on Apple Silicon.
Side note: still think that we also should fix the M1 behaviour (but in
the different patch set, obviously). And we shouldn't forget to update
this test after, I believe.
> + result[i] = testbitshift.testbitshift(1, 1, 1, rol(1ULL, i + 32))
<snipped>
> diff --git a/test/tarantool-tests/fix-bit-shift-generation/CMakeLists.txt b/test/tarantool-tests/fix-bit-shift-generation/CMakeLists.txt
> new file mode 100644
> index 00000000..f85f875b
> --- /dev/null
> +++ b/test/tarantool-tests/fix-bit-shift-generation/CMakeLists.txt
<snipped>
> diff --git a/test/tarantool-tests/fix-bit-shift-generation/libtestbitshift.c b/test/tarantool-tests/fix-bit-shift-generation/libtestbitshift.c
> new file mode 100644
> index 00000000..0785ebba
> --- /dev/null
> +++ b/test/tarantool-tests/fix-bit-shift-generation/libtestbitshift.c
> @@ -0,0 +1,8 @@
> +#include <stdint.h>
> +
> +uint64_t
> +testbitshift
> +(const int arg1, const int arg2, const int arg3, const uint64_t arg4)
> +{
> + return arg4;
> +}
I suggest to use more meaningful naming (like we need to get only 4th
argument of the function). Also, it helps with linewidth.
| uint64_t
| pick4(const int arg1, const int arg2, const int arg3, const uint64_t res)
| {
| return res;
| }
Feel free to ignore.
But if you prefer the new naming -- don't forget to change it in the Lua
test too.
Also, it is strange that the compiler doesn't warn about unused
arguments, but OK.
> --
> 2.40.1
>
--
Best regards,
Sergey Kaplun
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