Landing: e90e0f66051d

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Project / Subsystem

gcc / tree-optimization

Date

2026-09-07

Author

Shivam Gupta

Commit

e90e0f66051d338c1950d2cc9e36967552d75c3a

Source

github

Perf win

Yes

Breaking

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All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: e90e0f66051d338c1950d2cc9e36967552d75c3a
source_type: github
headline: tree-optimization: Recognize CLZ loop for signed non-negative values.
tldr: Compiler now recognizes CLZ (count leading zeros) optimization for loops involving signed non-negative values.
author: Shivam Gupta
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• loop-optimization
• signed-arithmetic
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/e90e0f66051d338c1950d2cc9e36967552d75c3a
date: 2026-09-07T00:00:00.000Z

The compiler’s loop iteration counting has been improved to recognize Count Leading Zeros (CLZ) optimizations for loops that use signed arithmetic right shifts on non-negative values. Previously, a strict unsigned type check prevented this optimization. The change modifies the is_rshift_by_1 function and adds non-negativity checks to loop iteration counting, enabling more efficient code generation for these cases.