Landing: 9edd8aa65a3c

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Project / Subsystem

gcc / vect

Date

2026-09-28

Author

Dominic P

Commit

9edd8aa65a3c2fb813412971c00981d6d466ab0f

Source

github

Perf win

Yes

Breaking

No

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project: gcc
subsystem: vect
patch_id: —
commit_hash: 9edd8aa65a3c2fb813412971c00981d6d466ab0f
source_type: github
headline: vect: Widen loop-invariant operands using their narrowest valid range
tldr: Vectorizer now uses narrow ranges of loop-invariant operands to enable more widening operations.
author: Dominic P
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • vectorization
• optimization
• performance
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/9edd8aa65a3c2fb813412971c00981d6d466ab0f
date: 2026-09-28T00:00:00.000Z

The GCC vectorizer can sometimes widen operands to match the result type, improving instruction efficiency. Previously, this widening was blocked if a loop-invariant operand had a range that didn’t fit within the result’s type, even if the operand’s actual range was much narrower. This change modifies the vectorizer to query the precise range of loop-invariant operands and use the narrowest type that can hold that range. This allows widening to occur more often, as seen in an x265 optimization that reduced instruction count.