Nick Desaulniers nickdesaulniers

This document explains how I would implement an SSA-based compiler if I was writing one today.

This document is intentionally opinionated. It just tells you how I would do it. This document is intended for anyone who has read about SSA and understands the concept, but is confused about how exactly to put it into practice. If you're that person, then I'm here to show you a way to do it that works well for me. If you're looking for a review of other ways to do it, I recommend this post.

My approach works well when implementing the compiler in any language that easily permits cyclic mutable data structures. I know from experience that it'll work great in C++, C#, or Java. The memory management of this approach is simple (and I'll explain it), so you won't have to stress about use after frees.

I like my approach because it leads to an ergonomic API by minimizing the amount of special cases you have to worry about. Most of the compiler is analyses and transformations ov

Here's a much more complete description of how I do SSA, beyond just how I do Phis.

This describes how I do SSA form, which avoids the need to have any coupling between CFG data structures and SSA data structures.

Let's first define a syntax for SSA and some terminology. Here's an example SSA node:

A = Add(B, C)

In reality, this will be a single object in your in-memory representation, and the names are really addresses of those objects. So, this node has an "implicit variable" called A; it's the variable that is implicitly assigned to when you execute the node. If you then do:

The semantics of inline are one of the areas where C and C++ are pretty different. This post is about the C++ semantics, but the history is interesting, so here's a short summary of it.

The meaning of "inline" is intuitively easy to understand: It gives the compiler a hint that it'd be nice if a function could be inlined. It gets a bit complicated because of two issues:

If the function ends up not being inlined, where should the definition of the function be emitted?
If the inline function contains a static local variable, should that be inlined? Should there be several copies of the static local, or just one?

Dumping games with Godmode9

Dumping games is the act of taking a game from your system or gamecart and copying it into a readable format onto your SD card. Dumping is perfectly legal if you keep the dumps to yourself, however sharing these dumps is piracy and is illegal.

This guide will tell you how to dump games from various formats and for various purposes. Dumping 3DS cartriges as .cia files is good if you want to install them to your system. Dumping them as .3ds files is good for emulators. Installed titles cannot be dumped as .3ds files. NDS cartiges can only be dumped as .nds files and cannot be installed (however, you can play them with emulators or flashcarts).

Dumping the RomFS of a game is primarily for romhacking purposess.

What is the Strict Aliasing Rule and Why do we care?

(OR Type Punning, Undefined Behavior and Alignment, Oh My!)

What is strict aliasing? First we will describe what is aliasing and then we can learn what being strict about it means.

In C and C++ aliasing has to do with what expression types we are allowed to access stored values through. In both C and C++ the standard specifies which expression types are allowed to alias which types. The compiler and optimizer are allowed to assume we follow the aliasing rules strictly, hence the term strict aliasing rule. If we attempt to access a value using a type not allowed it is classified as undefined behavior(UB). Once we have undefined behavior all bets are off, the results of our program are no longer reliable.

Unfortunately with strict aliasing violations, we will often obtain the results we expect, leaving the possibility the a future version of a compiler with a new optimization will break code we th

Hello software developers,

Please check your code to ensure you're not making one of the following mistakes related to cryptography.

I. General Mistakes

Writing your own home-grown cryptography primitives (For example: Mifare Classic)
- Exception: For the sake of learning, but don't deploy it in production.
Using a fast hash function (e.g. MD5, SHA256) for storing passwords. Use bcrypt instead.
Not using a cryptographically secure random number generator

	pushd /image/usr/src/linux-5.13.12
	make ARCH=x86_64 mrproper
	make ARCH=x86_64 INSTALL_HDR_PATH=/image/usr headers_install
	popd

	mkdir -p /image/var/tmp/build/compiler-rt-12.0.1
	pushd /image/var/tmp/build/compiler-rt-12.0.1
	cmake -D CMAKE_BUILD_TYPE=Release \
	-D CMAKE_C_COMPILER=clang \
	-D CMAKE_C_COMPILER_TARGET=x86_64-unknown-linux-musl \

	BR2_aarch64=y
	BR2_cortex_a57=y
	BR2_OPTIMIZE_3=y
	BR2_TOOLCHAIN_EXTERNAL=y
	BR2_TARGET_GENERIC_ROOT_PASSWD="root"
	BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
	BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
	BR2_PACKAGE_BASH=y
	BR2_PACKAGE_HTOP=y
	BR2_PACKAGE_VIM=y

	Why do compilers even bother with exploiting undefinedness signed overflow? And what are those
	mysterious cases where it helps?

	A lot of people (myself included) are against transforms that aggressively exploit undefined behavior, but
	I think it's useful to know what compiler writers are accomplishing by this.

	TL;DR: C doesn't work very well if int!=register width, but (for backwards compat) int is 32-bit on all
	major 64-bit targets, and this causes quite hairy problems for code generation and optimization in some
	fairly common cases. The signed overflow UB exploitation is an attempt to work around this.

	#include <iostream>

	#define _USE_MATH_DEFINES
	#include <cmath>

	#include <SDL2/SDL.h>
	#include <SDL2/SDL_opengl.h>

	constexpr int SCREEN_WIDTH = 800;
	constexpr int SCREEN_HEIGHT = 600;