Zen 4 and 5 receive up to 12% performance boost thanks to new GCC compiler patch

AMD has published a new patch for the GNU Compiler Collection (GCC) surrounding Zen 5 and Zen 4 CPUs' branch predictors, helping boost the performance of Zen 5 CPUs by 12% and 9% for Zen 4. Reported by Phoronix, the new patch features just two lines, bumping the branch misprediction scale by three in the cost tables for both architectures.

The aforementioned performance results were taken from benchmarks using SPEC, or Standard Performance Evaluation Corporation's CPU benchmark. Not every app will gain an exact 9% or 12% performance improvement, but the SPEC benchmark shows what the average performance uplift could be on average across a variety of workloads.

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The GNU Compiler Collection (GCC) is a collection of compilers that support various programming languages, hardware, and operating systems. In the case of CPUs, AMD uses GCC to program its CPUs on how they should run instructions on the chip, including the way the chip operates its branch predictor.

Phoronix reports that the new patch is expected to debut next year as part of GCC 17, however, the outlet also suggested the patch could be "back-ported" to the GCC 16.3 release. If true, we could see the patch drop this year rather than next year.

Frequently Asked Questions

Open a question for an answer from TweakTown's coverage of this news, or ask your own below.

Question #1

How were the 12% (Zen 5) and 9% (Zen 4) performance numbers measured and which benchmark was used?

Phoronix reported the performance gains after testing with the SPEC benchmark, the Standard Performance Evaluation Corporation CPU benchmark. The 12% uplift for Zen 5 and 9% for Zen 4 come from those SPEC results and represent an average performance uplift across a variety of workloads.

Question #2

Will the GCC patch be included in GCC 17 or is it likely to be back-ported to GCC 16.3 this year?

Answer question

Question #3

Which types of workloads are most likely to benefit from the branch predictor improvements reported in the article?

The article says the reported gains come from SPEC CPU benchmarks, so workloads represented in the SPEC suite are most likely to see the improvement. It also notes a similar 2024 branch prediction update produced roughly a 10% performance improvement for gaming and productivity workloads, indicating those types may particularly benefit.

Question #4

Can end users expect the same percentage gains in real-world applications and games as shown by the SPEC benchmark?

Not necessarily. The article says not every app will gain an exact 9% or 12% improvement; SPEC shows what the average performance uplift could be across a variety of workloads. It also notes a prior update that delivered roughly a 10% improvement for gaming and productivity workloads, suggesting some real-world gains are possible but not guaranteed.

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The results of this patch mimic similar behavior that we saw back in 2024, when AMD published branch prediction improvements for Zen 3, Zen 4, and Zen 5 for Windows 11 23H2. The improvements in that update provided roughly a 10% performance improvement for gaming and productivity workloads.