Landing: b0a84b610038

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Project / Subsystem

gcc / tree-optimization

Date

2026-06-04

Author

Zhou Xuhang

Commit

b0a84b6100389c5b24658743252a7ff259ba0816

Source

github

Perf win

Yes

Breaking

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All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: b0a84b6100389c5b24658743252a7ff259ba0816
source_type: github
headline: tree-optimization: Recognize widened unsigned multiply overflow checks
tldr: GCC now recognizes and optimizes widened unsigned multiply overflow checks, canonicalizing them to a specific overflow detection pattern.
author: Zhou Xuhang
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• tree-optimization
• arithmetic
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/b0a84b6100389c5b24658743252a7ff259ba0816
date: 2026-06-04T00:00:00.000Z

GCC’s tree optimization pass can now recognize and optimize overflow checks involving widened unsigned multiplications. The compiler canonicalizes patterns where a multiplication result is shifted and compared against the maximum value of the narrow type into a widened comparison form. This form is then further simplified to IFN_MUL_OVERFLOW when the target architecture supports direct unsigned multiply-overflow instructions, enabling more efficient code generation.