Blueprint 05 Compiler

Source: docs/blueprint/05-compiler.md in the main repository.

Layer 5 — Compiler Exploitation & Language Modernity

Force the compiler to emit the machine code you mean — then keep that code small.

Tooling deep-dive (ARM vs Intel, cross-compilation, flags):
docs/tutorials/modern-cpp-tooling-arm-intel.md.

Checklist

Topic	Status
C++26 as project default	SHIPPED
constexpr / consteval	DOC + encourage in modules
CRTP / static polymorphism	ll::StaticInterface
[[likely]] / [[unlikely]]	LL_LIKELY / LL_UNLIKELY
LTO / PGO / ISA flags	DOC (portable defaults in CMake)
i-cache discipline	DOC (critical)

Compile-time work

constexpr double tick_size = 0.01;
consteval int scale() { return 100; }

Push parsing of static config, hash tables of constants, and protocol tags to compile time when possible.

Polymorphism without vtables

struct Feed : ll::StaticInterface<Feed> {
  void on_tick() { /* ... */ }
};
// call feed.self().on_tick() — resolved statically, no vptr

Prefer std::variant + std::visit for closed sets of message types.

Branch hints

if (LL_UNLIKELY(error)) {
  handle_cold_path();
}

Cold error paths should not pollute the i-cache working set of the hot loop.

Recommended flags (profile-dependent)

Goal	Flags
Portable release	-O3 -flto (optional)
Local max performance	-O3 -flto -march=native (not for portable artifacts)
PGO	build + train + rebuild with profile data

This repo avoids hard-coding -march=native in shared CMake so CI and laptops stay portable; document native builds for production images.

i-cache

Instruction cache misses from huge binaries often hurt more than one extra data load.

Practices:

• Split diagnostics / logging from hot TUs
• Avoid heavy templates on the absolute critical path
• Prefer few, predictable branches
• Profile with perf (icache, iTLB)

Module

#include "ll/branch.hpp"