Compiler Optimizations (Deep)

Purpose

Explain optimization phases beyond flags: mid-level IR opts, register allocation, instruction selection/scheduling, vectorization boundaries, PGO, and post-link BOLT — bridging skills/compilers/pgo and LLVM/GCC internals.

When to Use

• -O3 did not vectorize a hot loop
• Teaching why register pressure causes spills
• Planning PGO or BOLT deployment
• Understanding pass interaction (e.g., LICM before vectorize)

Workflow

1. Compiler pipeline map