Thanks! LGTM

Hi, Sergey!
Thanks for the review!
Fixed your comments and force-pushed the branch.

On 27.06.25, Sergey Bronnikov wrote:

Hi, Sergey,

thanks for the patch! LGTM with a minor two comments below.

Sergey

On 6/26/25 18:12, Sergey Kaplun wrote:

From: Mike Pall <mike>

Thanks to Peter Cawley.

(cherry picked from commit 0fa2f1cbcf023ad0549f1428809e506fa2c78552)

The arm64 emitting of load/store operation works incorrectly in the
case when at least one offset of load/store to be fused into ldp/stp is
misaligned. In this case this misaligning is ignored, and instructions
are fused, which leads to loading/storing from/to at least one incorrect
address.

For example, the following instructions:
| stur  w0, [x1, #17]
| stur  w0, [x1, #21]

May be fused to the following:
| stp   w0, w0, [x1, #16]

This patch prevents fusion in this case by testing the alignment with
the help of bitwise ROR by the alignment value. In case of misaligned
offset, the value overflows the 7-bit length mask in the check.

The negative immediate (7-bit width including sign bit) is limited by
the corresponding addition of `64 << sc` (it is harmless in the case of
positive values).

Sergey Kaplun:
* added the description and the test for the problem

Part of tarantool/tarantool#11278
---

Related issues:
*https://github.com/LuaJIT/LuaJIT/issues/1056
*https://github.com/tarantool/tarantool/issues/11278
Branch:https://github.com/tarantool/luajit/tree/skaplun/lj-1056-arm64-ldp-sdp-misaligned-fusing

  src/lj_emit_arm64.h                           |  2 +-
  ...6-arm64-ldp-sdp-misaligned-fusing.test.lua | 98 +++++++++++++++++++
  2 files changed, 99 insertions(+), 1 deletion(-)
  create mode 100644 test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua

diff --git a/src/lj_emit_arm64.h b/src/lj_emit_arm64.h
index 30cd3505..5c1bc372 100644
--- a/src/lj_emit_arm64.h
+++ b/src/lj_emit_arm64.h

<snipped>

diff --git a/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
new file mode 100644
index 00000000..5d03097e
--- /dev/null
+++ b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
@@ -0,0 +1,98 @@
+local tap = require('tap')
+local ffi = require('ffi')
+
+-- This test demonstrates LuaJIT's incorrect emitting of LDP/STP
+-- instructions from LDUR/STUR instructions with misaligned offset
+-- on arm64.
+-- See alsohttps://github.com/LuaJIT/LuaJIT/issue/1056.

s/issue/issues/

Fixed, thanks!

===================================================================
diff --git a/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
index 815da15d..5ff040e7 100644
--- a/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
+++ b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
@@ -4,7 +4,7 @@ local ffi = require('ffi')
 -- This test demonstrates LuaJIT's incorrect emitting of LDP/STP
 -- instructions from LDUR/STUR instructions with misaligned offset
 -- on arm64.
--- See also https://github.com/LuaJIT/LuaJIT/issue/1056.
+-- See also https://github.com/LuaJIT/LuaJIT/issues/1056.
 local test = tap.test('lj-1056-arm64-ldp-sdp-misaligned-fusing'):skipcond({
   ['Test requires JIT enabled'] = not jit.status(),
 })
===================================================================

+local test = tap.test('lj-1056-arm64-ldp-sdp-misaligned-fusing'):skipcond({
+  ['Test requires JIT enabled'] = not jit.status(),
+})
+

<snipped>

+
+test:is(resl, 0x4030201, 'pair of misaligned loads, left')
+test:is(resr, 0x8070605, 'pair of misaligned loads, right')

What does mean these magic numbers? Please add a comment or

use a variable with self-explained name. Here and below.

Added the comments nearby, see the corresponding patch below:

===================================================================
diff --git a/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
index 5d03097e..815da15d 100644
--- a/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
+++ b/test/tarantool-tests/lj-1056-arm64-ldp-sdp-misaligned-fusing.test.lua
@@ -81,6 +81,8 @@ for _ = 1, N_ITERATIONS do
   resr = ffi.cast('int32_t *', ptr + 5)[0]
 end
 
+-- Values are resulted from the `init_buf()` function with the
+-- corresponding offset.
 test:is(resl, 0x4030201, 'pair of misaligned loads, left')
 test:is(resr, 0x8070605, 'pair of misaligned loads, right')
 
@@ -92,6 +94,8 @@ for _ = 1, N_ITERATIONS do
   resl = ffi.cast('int32_t *', ptr)[0]
 end
 
+-- Values are resulted from the `init_buf()` function with the
+-- corresponding offset.
 test:is(resl, 0x3020100, 'aligned / misaligned load, aligned')
 test:is(resr, 0x8070605, 'aligned / misaligned load, misaligned')
 
===================================================================

<snipped>