Optimization Levels

Porffor supports multiple optimization levels controlled by the -O flag, similar to traditional compilers like GCC and Clang.

Optimization Levels

-O0: No Optimization

-O0

flag

Disable all optimizations.

porf -O0 script.js

When -O0 is set, the optimizer immediately returns without performing any transformations.Use cases:

Debugging compiled output
Fastest compilation times
Testing unoptimized code paths

Source reference: source/compiler/opt.js:8

-O1: Basic Optimization (Default)

-O1

flag

default:"true"

Enable basic optimizations. This is the default optimization level.

porf -O1 script.js
# or simply
porf script.js

Optimizations performed:

Peephole optimizations (local.get/local.set consolidation)
Constant folding
Dead code elimination (unused blocks)
Redundant conversion removal (i32→f64→i32, etc.)
Type conversion optimization
Instruction combining (local.set + local.get → local.tee)

Examples:

# Before optimization
local.set 0
local.get 0

# After -O1
local.tee 0

# Before optimization
local.get 0
drop

# After -O1
# (removed)

# Before optimization
i32.const 0
i32.eq

# After -O1
i32.eqz

Source reference: source/compiler/opt.js:1-248

-O2: Advanced Optimization

-O2

flag

Enable advanced optimizations. May be unstable.

porf -O2 script.js

Includes all -O1 optimizations plus:

Cyclone optimizer (partial constant evaluation)
More aggressive transformations

When -O2 is enabled, the Cyclone optimizer is automatically activated unless explicitly disabled.

-O2 enables experimental optimizations that may be unstable. Use with caution in production.

Source reference: source/compiler/index.js:88-91

-O3: Maximum Optimization

-O3

flag

Enable maximum optimizations (experimental).

porf -O3 script.js

Currently has similar behavior to -O2. Additional optimizations may be added in the future.Source reference: source/runtime/index.js:47

Cyclone Optimizer

The Cyclone optimizer is Porffor’s partial constant evaluator - it’s fast and powerful (hence the name “cyclone”).

--cyclone

flag

Explicitly enable or disable the Cyclone optimizer.

# Enable Cyclone (automatically enabled with -O2)
porf --cyclone script.js

# Disable Cyclone even with -O2
porf -O2 --no-cyclone script.js

Cyclone performs:

Constant propagation and folding
Dead local elimination
Stack-based partial evaluation
Control flow simplification
Type-based optimizations

Source reference: source/compiler/cyclone.js:1-4

--cyclone-log

flag

Log Cyclone optimizer performance and results.

porf --cyclone --cyclone-log script.js

Displays:

Per-function optimization results (ops before → after)
Total optimization time
Size difference in bytes

Source reference: source/compiler/index.js:132-147

Profile-Guided Optimization

--pgo

flag

Enable profile-guided optimization.

porf --pgo script.js

PGO runs the code to collect runtime profiling data, then uses that data to guide optimizations.Source reference: source/compiler/index.js:93

--pgo-log

flag

Log PGO performance and results.

porf --pgo --pgo-log script.js

Source reference: source/compiler/index.js:114-124

Optimization Configuration

Wasm Optimization Runs

--opt-wasm-runs

number

default:"2"

Number of optimization passes to run on each function.

porf --opt-wasm-runs=5 script.js

More runs can catch additional optimization opportunities but increase compilation time.Source reference: source/compiler/opt.js:21

Optimization Logging

--opt-log

flag

Log individual optimizations as they’re applied.

porf --opt-log script.js

Useful for debugging optimizer behavior and understanding what transformations are applied.Source reference: source/compiler/opt.js:55

Specific Optimizations

Unused Code Elimination

--opt-unused

boolean

default:"true"

Remove unused code and variables.

porf --no-opt-unused script.js

Fast Length

--fast-length

flag

Non-compliant optimization to make .length property access faster.

porf --fast-length script.js

This assumes .length always returns a number without runtime type checking. This breaks spec compliance but can provide performance benefits.Source reference: source/compiler/codegen.js:1887

Type Optimizations

--opt-types

boolean

default:"true"

Optimize based on type information.

porf --no-opt-types script.js

Enables type-guided optimizations throughout the compiler.

--rm-unused-types

boolean

default:"true"

Remove unused type checking code.

porf --no-rm-unused-types script.js

Comparison Table

Feature	-O0	-O1 (default)	-O2	-O3
Peephole optimizations	❌	✅	✅	✅
Constant folding	❌	✅	✅	✅
Dead code elimination	❌	✅	✅	✅
Cyclone optimizer	❌	❌	✅	✅
Compile time	Fastest	Fast	Slower	Slower
Output size	Largest	Smaller	Smallest	Smallest
Stability	Stable	Stable	Experimental	Experimental

Examples

Debug build (fast compilation)

porf -O0 -d script.js

Production build (balanced)

porf -O1 script.js output.wasm

Aggressive optimization

porf -O2 --pgo --wasm-opt script.js output.wasm

Maximum optimization with logging

porf -O2 --cyclone-log --pgo-log --opt-log script.js

Get Started

Core Concepts

CLI Commands

Configuration

Advanced Features

Guides

Optimization Levels