Landing: f6971e28e71e

← All landings

Project / Subsystem

gcc / gcc

Date

2026-05-28

Author

Roger Sayle

Commit

f6971e28e71eda7f8a1d1247f57ee7f16828864d

Source

github

Perf win

Yes

Breaking

View on GitHub →

All attributes

project: gcc
subsystem: gcc
patch_id: —
commit_hash: f6971e28e71eda7f8a1d1247f57ee7f16828864d
source_type: github
headline: x86_64: Improve SSE Code Generation for 128-bit Integer Comparisons
tldr: Enables scalar-to-vector transformation for 128-bit integer comparisons on x86_64 with SSE, resulting in more efficient code.
author: Roger Sayle
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • x86_64
• sse
• optimization
• code generation
• vectorization
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/f6971e28e71eda7f8a1d1247f57ee7f16828864d
date: 2026-05-28T00:00:00.000Z

The i386 STV pass has been enhanced to handle SUBREG conversions for TImode values, which allows scalar-to-vector transformation of 128-bit integer comparisons when compiling for x86_64 with SSE. This optimization avoids transferring 128-bit vectors to the scalar unit for equality testing, resulting in significantly more efficient code. For example, comparing two __m128i vectors for equality now uses pxor and ptest instructions, avoiding several move and logical operations.