Luke McCarthy ljmccarthy

GCC compiler optimization for ARM-based systems

2017-03-03 fm4dd

The gcc compiler can optimize code by taking advantage of CPU specific features. Especially for ARM CPU's, this can have impact on application performance. ARM CPU's, even under the same architecture, could be implemented with different versions of floating point units (FPU). Utilizing full FPU potential improves performance of heavier operating systems such as full Linux distributions.

-mcpu, -march: Defining the CPU type and architecture

These flags can both be used to set the CPU type. Setting one or the other is sufficient.

	#!/usr/bin/python
	# fix_date.py - corrects the received date in IMAP folders.

	# Description:
	# When moving mail between IMAP servers, the received date can become
	# reset to the date when the message was added to the new server. This
	# script attempts to fix this by setting the received date to the date the
	# message was sent.

	# Usage:

	# source:http://geocities.com/SiliconValley/heights/7052/opcode.txt
	From: [email protected] (Mark Hopkins)
	Newsgroups: alt.lang.asm
	Subject: A Summary of the 80486 Opcodes and Instructions

	(1) The 80x86 is an Octal Machine
	This is a follow-up and revision of an article posted in alt.lang.asm on
	7-5-92 concerning the 80x86 instruction encoding.

	The only proper way to understand 80x86 coding is to realize that ALL 80x86

	meaning cmp A, B sign flags
	------------------------------- ------- --------------- --------------- -------------------
	equal eq A == B - Z == 1
	not equal ne A != B - Z == 0

	carry set cs,hs A >= B unsigned C == 1
	carry clear cc,lo A < B unsigned C == 0
	higher hi A > B unsigned C == 1 && Z == 0
	lower or same ls A <= B unsigned !(C == 1 && Z == 0)

	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8">
	<title>Full-screen Canvas</title>
	</head>
	<body style="background:black">
	<canvas id="canvas" style="position:fixed;background:green;">
	Sorry, your browser does not appear to support HTML5 Canvas element.
	</canvas>

	git clean -xfd
	git submodule foreach --recursive git clean -xfd
	git reset --hard
	git submodule foreach --recursive git reset --hard
	git submodule update --init --recursive

	#define _XOPEN_SOURCE 700
	#include <signal.h>
	#include <unistd.h>

	int main()
	{
	sigset_t set;
	int status;

	if (getpid() != 1) return 1;

	! urxvt
	URxvt*buffered: true
	URxvt*cursorBlink: true
	URxvt*underlineColor: yellow
	URxvt*font: xft:inconsolata:size=10:antialias=true
	URxvt*depth: 32
	URxvt*borderless: 1
	URxvt*scrollBar: false
	URxvt*loginShell: true
	Urxvt*secondaryScroll: true # Enable Shift-PageUp/Down in screen