From: Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Sergey Ostanevich <sergos@tarantool.org>, Maxim Kokryashkin <m.kokryashkin@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: [Tarantool-patches] [PATCH luajit 3/3] x86/x64: Fix loop realignment. Date: Wed, 18 Jan 2023 23:16:56 +0300 [thread overview] Message-ID: <673614b0d270047c096b156f5a886211770c4ac1.1674068996.git.skaplun@tarantool.org> (raw) In-Reply-To: <cover.1674068996.git.skaplun@tarantool.org> From: Mike Pall <mike> (cherry picked from commit 522d2073da4be2af79db4728cbb375db0fbdfc48) `asm_intarith()` function may try to drop `test r, r` instruction before the Jcc instruction. However, in case when Jcc instruction is "Jump short if ..." instruction (i.e. has no 0F opcode prefix like "Jump near if ..."), the `test` instruction is dropped when shouldn't be, due to memory miss. As the result, the loop can't be realigned later in `asm_loop_fixup` due to target to jump isn't aligned and the assertion fails. This patch adds the additional check for 0F opcode in `asm_intarith()`. Sergey Kaplun: * added the description and the test for the problem Part of tarantool/tarantool#8069 --- src/lj_asm_x86.h | 5 +++-- .../lj-556-fix-loop-realignment.test.lua | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+), 2 deletions(-) create mode 100644 test/tarantool-tests/lj-556-fix-loop-realignment.test.lua diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h index 8efda8e5..e6c42c6d 100644 --- a/src/lj_asm_x86.h +++ b/src/lj_asm_x86.h @@ -2068,8 +2068,9 @@ static void asm_intarith(ASMState *as, IRIns *ir, x86Arith xa) int32_t k = 0; if (as->flagmcp == as->mcp) { /* Drop test r,r instruction. */ MCode *p = as->mcp + ((LJ_64 && *as->mcp < XI_TESTb) ? 3 : 2); - if ((p[1] & 15) < 14) { - if ((p[1] & 15) >= 12) p[1] -= 4; /* L <->S, NL <-> NS */ + MCode *q = p[0] == 0x0f ? p+1 : p; + if ((*q & 15) < 14) { + if ((*q & 15) >= 12) *q -= 4; /* L <->S, NL <-> NS */ as->flagmcp = NULL; as->mcp = p; } /* else: cannot transform LE/NLE to cc without use of OF. */ diff --git a/test/tarantool-tests/lj-556-fix-loop-realignment.test.lua b/test/tarantool-tests/lj-556-fix-loop-realignment.test.lua new file mode 100644 index 00000000..9a8e6098 --- /dev/null +++ b/test/tarantool-tests/lj-556-fix-loop-realignment.test.lua @@ -0,0 +1,18 @@ +local tap = require('tap') + +local test = tap.test('lj-505-fold-icorrect-behavior') +test:plan(1) + +-- Test file to demonstrate JIT misbehaviour for loop realignment +-- in LUAJIT_NUMMODE=2. See also +-- https://github.com/LuaJIT/LuaJIT/issues/556. + +jit.opt.start('hotloop=1') + +local s = 4 +while s > 0 do + s = s - 1 +end + +test:ok(true, 'loop is compiled and ran successfully') +os.exit(test:check() and 0 or 1) -- 2.34.1
next prev parent reply other threads:[~2023-01-18 20:21 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-01-18 20:19 [Tarantool-patches] [PATCH luajit 0/3] Dualnumber mode fixes Sergey Kaplun via Tarantool-patches 2023-01-18 20:16 ` [Tarantool-patches] [PATCH luajit 1/3] sysprof: fix interval parsing in dual-number mode Sergey Kaplun via Tarantool-patches 2023-01-24 14:16 ` Maxim Kokryashkin via Tarantool-patches 2023-01-26 15:55 ` sergos via Tarantool-patches 2023-01-30 9:39 ` Sergey Kaplun via Tarantool-patches 2023-01-18 20:16 ` [Tarantool-patches] [PATCH luajit 2/3] ci: introduce workflow for exotic builds Sergey Kaplun via Tarantool-patches 2023-01-24 14:20 ` Maxim Kokryashkin via Tarantool-patches 2023-01-26 21:12 ` sergos via Tarantool-patches 2023-01-30 9:51 ` Sergey Kaplun via Tarantool-patches 2023-02-01 8:27 ` Igor Munkin via Tarantool-patches 2023-02-01 8:52 ` Sergey Kaplun via Tarantool-patches 2023-02-02 8:54 ` sergos via Tarantool-patches 2023-01-18 20:16 ` Sergey Kaplun via Tarantool-patches [this message] 2023-01-19 10:17 ` [Tarantool-patches] [PATCH luajit 3/3] x86/x64: Fix loop realignment Sergey Kaplun via Tarantool-patches 2023-01-24 15:13 ` Maxim Kokryashkin via Tarantool-patches 2023-01-26 7:06 ` Sergey Kaplun via Tarantool-patches 2023-01-26 14:45 ` Maxim Kokryashkin via Tarantool-patches 2023-01-26 21:22 ` sergos via Tarantool-patches 2023-02-20 9:56 ` [Tarantool-patches] [PATCH luajit 0/3] Dualnumber mode fixes Igor Munkin via Tarantool-patches
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