[MDEV-26720] Suboptimal translation of single-bit std::atomic::fetch_or() and fetch_and() - Jira

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Details

Type: Bug
Status: Closed (View Workflow)
Priority: Major
Resolution: Fixed
Affects Version/s: 10.5, 10.6
Fix Version/s: 10.5.13, 10.6.5
Component/s: Storage Engine - InnoDB
Labels:
- performance
Environment:
IA-32, AMD64, GCC, clang (and derivatives such as Xcode, icc), Microsoft C compiler

Description

This is actually a compiler bug. The Intel 80386 processor introduced some bit operations that would be the perfect translation for atomic single-bit read-modify-and-write operations. Alas, even the latest compilers as of today (GCC, clang, Microsoft C compiler) would generate a loop around LOCK CMPXCHG instead of emitting the instructions LOCK BTS (fetch_or()), LOCK BTR (fetch_and()), LOCK BTC (fetch_xor()).

We have several single-bit fetch_and() and fetch_or() operations that can be optimized to LOCK BTS or LOCK BTR, similar to (this fix of ~~MDEV-26467~~).

Attachments

Issue Links

causes

MDEV-27402 Error "'asm goto' constructs are not supported yet" on macOS with Xcode 9.4.1

Closed

relates to

MDEV-27667 Fix MDEV-26720 on 64-bit Microsoft Windows

Closed

MDEV-26467 Unnecessary compare-and-swap loop in futex-based synchronization

Closed

Activity

People

Assignee:: Marko Mäkelä

Reporter:: Marko Mäkelä

Votes:: 0 Vote for this issue

Watchers:: 1 Start watching this issue

Dates

Created:: 2021-09-29 16:17

Updated:: 2022-01-28 14:42

Resolved:: 2021-10-03 12:09

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