Landing: 91cca3ac45e7
Project / Subsystem
gcc / gcc/optimization
Date
2026-07-08
Author
Konstantinos Eleftheriou
Commit
91cca3ac45e7f286e770536030da982d65615d4f
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc/optimization
- patch_id
- —
- commit_hash
- 91cca3ac45e7f286e770536030da982d65615d4f
- source_type
- github
- headline
- forwprop: Add long-multiply ladder variants
- tldr
- Extends long-multiply optimization to recognize and fold 'ladder' variants involving shifted intermediate sums.
- author
- Konstantinos Eleftheriou
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • gcc
- • optimization
- • forwprop
- • long-multiply
- • ladder
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-08T00:00:00.000Z
This commit enhances the forwprop optimization pass by adding support for ‘ladder’ variants of long multiplication. These variants propagate carries through a series of mask, shift, and add operations on intermediate sums. The optimization now recognizes patterns like mul_ladder_sum1, mul_ladder_sum2, and mul_ladder_sum3, allowing the compiler to fold these complex multiplication sequences into more efficient code. This improves optimization for targets supporting these patterns and addresses a reported issue (PR tree-optimization/107090).