Go: Compiler Speed Gains, and Two Reverts Worth Remembering
The compiler team landed real performance wins in division and cryptographic code, but two aggressive optimizations from earlier releases got pulled after breaking builds and benchmarks in production. A quiet security fix in the reverse proxy also closed off an unexpected request-smuggling path.
Duration: PT2M26S
Episode overview
This episode is a short developer briefing from Go.
It explains recent repository work in plain language.
- Show: Go
- Published: 2026-07-18T13:06:03Z
- Audio duration: PT2M26S
Transcript excerpt
This excerpt keeps the crawler page concise. Listen to the episode or use the RSS feed for the full update.
Good day. It's July 18, 2026, and this is Go.
The headline today is a tale of two kinds of performance work: the kind that shipped clean, and the kind that had to be walked back.
On the win side, Michael Matloob landed a fused multiply-subtract rewrite for AMD64's v3 instruction set, tightening up floating point codegen. MITSUNARI Shigeo contributed a clever optimization for 32-bit unsigned division, using a pre-shifted magic constant to cut division time by up to 38 percent on modern 64-bit…
But two other optimizations didn't survive contact with reality. Jake Bailey reverted a change that optimized how the runtime loads type flags, after it broke a build tool called relui. And Michael Pratt reverted a change meant to speed up compiling large synthetic init functions, after it caused map initialization…
On the security and correctness front, Damien Neil closed a subtle issue in the HTTP reverse proxy: it was forwarding "Upgrade: h2c" headers, which could let a client's request bypass the proxy's own handlers entirely if the backend supported that deprecated protocol switch. That's now blocked by default.
Smaller but useful: testing panics for parallel test conflicts now name the…
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- The Great Doc Cleanup
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