Landing: 5b40e9d181bf

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Project / Subsystem

gcc / forwprop

Date

2026-07-30

Author

Daniel Barboza

Commit

5b40e9d181bfe268ee9922c6af525bc5dab2604c

Source

github

Perf win

Yes

Breaking

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All attributes

project: gcc
subsystem: forwprop
patch_id: —
commit_hash: 5b40e9d181bfe268ee9922c6af525bc5dab2604c
source_type: github
headline: Simplifies division and modulo by powers of two in PHI nodes.
tldr: New forward propagation pass simplifies DIV/MOD by powers of two into RSHIFT/BIT_AND within PHI nodes.
author: Daniel Barboza
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• SSA
• integer arithmetic
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/5b40e9d181bfe268ee9922c6af525bc5dab2604c
date: 2026-07-30T00:00:00.000Z

A new forward propagation pass, simplify_phi_result_movdiv, is introduced to simplify division and modulo operations where the divisor is a power of two within PHI nodes. It transforms DIV into RSHIFT and MOD into BIT_AND, provided certain conditions on the operands are met. This change resolves most use cases for PR101179 by enabling these simplifications for positive power-of-two divisors and specific conditions on the PHI node’s arguments.