Landing: 006150ddc408
Project / Subsystem
gcc / gcc/optimization
Date
2026-07-08
Author
Konstantinos Eleftheriou
Commit
006150ddc40844105eb99bc6514267314715f6dc
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc/optimization
- patch_id
- —
- commit_hash
- 006150ddc40844105eb99bc6514267314715f6dc
- source_type
- github
- headline
- forwprop: Add long-multiply low-plus variant
- tldr
- Enhances long-multiply optimization by recognizing and folding a 'low-plus' variant involving cross-product and shifted low parts.
- author
- Konstantinos Eleftheriou
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • gcc
- • optimization
- • forwprop
- • long-multiply
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-08T00:00:00.000Z
This commit extends the forwprop optimization pass to recognize a ‘low-plus’ variant of long multiplication. This variant involves the cross-product of high and low parts of the operands, combined with a shifted low partial product. The optimization now correctly folds this pattern, especially when it’s part of a two-carry long multiplication, deferring the fold if conditional comparisons still require intermediate values. This improves code generation for specific multiplication scenarios.