Module optimize 

Peephole optimizations for instruction encoding. Peephole optimizations for x86/x86-64 instructions.

These optimizations transform instructions into shorter or more efficient encodings without changing observable behavior. They are applied when OptLevel::Size is active (the default).

Optimizations

• Zero-idiom: mov reg, 0 → xor reg, reg (saves 3–5 bytes, faster on modern CPUs)
• REX elimination: op r64, imm where imm fits i32 and result is zero-extended from 32-bit
• NOP elimination: mov reg, reg with same register → nop or removed
• Test conversion: and reg, reg → test reg, reg (identical flags, does not write reg)
• Short AL/AX/EAX/RAX forms: Uses accumulator-specific short encodings
• Sign-extended immediate: mov r64, imm where imm fits i32 → mov r32, imm32

Functions

optimize_instruction

Apply peephole optimizations to an instruction (mutates in place).