Landing: 4765a2e39807

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Project / Subsystem

gcc / tree-optimization

Date

2026-04-27

Author

Netanel Komm

Commit

4765a2e3980749c9eebd313b53d5be5aecf855be

Source

github

Perf win

Yes

Breaking

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project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: 4765a2e3980749c9eebd313b53d5be5aecf855be
source_type: github
headline: Tree-optimization Lowers mempcpy to memcpy When Result is Unused.
tldr: The compiler now optimizes `mempcpy` calls to `memcpy` when the return value is ignored, potentially improving performance.
author: Netanel Komm
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • tree-optimization
• memcpy
• mempcpy
• gimple
• performance
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/4765a2e3980749c9eebd313b53d5be5aecf855be
date: 2026-04-27T00:00:00.000Z

The GIMPLE folding pass now transforms __builtin_mempcpy into __builtin_memcpy when the return value of mempcpy is unused. Since many targets have highly optimized memcpy implementations, this transformation can improve code generation. New tests were added to ensure both the unfolded and folded mempcpy are properly handled.