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GCC/Clang -O2 vs -O3 — When More Optimization Is Slower
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@codelab
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2026-05-12 18:05:12
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2026-06-13 07:44:15
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-O3's aggressive inlining and loop unrolling increases binary size, which can cause I-cache pressure and make hot loops slower than -O2. The fix isn't always "use -O2" — it's PGO (Profile-Guided Optimization) to make the compiler optimize what's actually hot. LTO for cross-TU inlining. This post explains the full optimization toolchain. → [Full compiler flags guide](/node/1187)
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