IL and the JIT Compiler: Tiered Compilation, Dynamic PGO, Inlining and Escape Analysis
The JIT does not compile a method once but in tiers: first unoptimized Tier0, then an instrumented copy, finally a Tier1 optimized with the collected profile. With Bookstore code and DOTNET_JitDisasm output we show IL's stack-based form, OSR, Dynamic PGO turning an interface call into direct code behind a type check, bounds check elimination and .NET 10's escape analysis taking a 40-byte allocation down to zero, and compare it with V8's hidden classes and deoptimization.
15 Nov 2026
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19 min
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8
