| Vex is a minimalistic markup language with the motto "form without meaning". | |
| This is going to @italic=really hurt. | |
| // @author: Per Vognsen | |
| // @version: 1.3 | |
| The weather forecast for @date is @weather. | |
| @list{ |
| Suppose you are writing a simple one-pass compiler in the Wirth style, and you want to | |
| target non-RISC architectures like the x86 where conditional operations use shared condition state. | |
| Case 1: | |
| if (x <= y) z = w | |
| CMP x, y | |
| JGT skip | |
| MOV z, w | |
| skip: |
| #include "mu.h" | |
| #define _CRT_SECURE_NO_WARNINGS | |
| #include <malloc.h> | |
| #define _USE_MATH_DEFINES | |
| #include <math.h> | |
| #define _NO_CRT_STDIO_INLINE | |
| #include <stdio.h> | |
| #include <stdarg.h> | |
| #define NO_STRICT |
| /* ======================================================================== | |
| $File: tools/ctime/ctime.c $ | |
| $Date: 2016/05/08 04:16:55PM $ | |
| $Revision: 7 $ | |
| $Creator: Casey Muratori $ | |
| $Notice: | |
| The author of this software MAKES NO WARRANTY as to the RELIABILITY, | |
| SUITABILITY, or USABILITY of this software. USE IT AT YOUR OWN RISK. |
| 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. |
This is my little Christmas-break experiment trying to (among other things) reduce the amount of generated code for containers.
THIS CODE WILL CONTAIN BUGS AND IS ONLY PRESENTED AS AN EXAMPLE.
The C++ STL is still an undesirable library for many reasons I have extolled in the past. But it's also a good library. Demons lie in this here debate and I have no interest in revisiting it right now.
The goals that I have achieved with this approach are:
| // quick hack job by @mmalex | |
| // thanks to libhid author and @johndrinkwater and https://github.com/chrippa/ds4drv | |
| #include <stdio.h> | |
| #include "hidapi.h" // using http://www.signal11.us/oss/hidapi/ | |
| typedef unsigned char u8; | |
| typedef unsigned short u16; | |
| typedef unsigned int u32; | |
| #pragma pack(push, 1) |
Memory Optimization (Christer Ericson, GDC 2003)
http://realtimecollisiondetection.net/pubs/GDC03_Ericson_Memory_Optimization.ppt
Cache coherency primer (Fabian Giesen)
https://fgiesen.wordpress.com/2014/07/07/cache-coherency/
Code Clinic 2015: How to Write Code the Compiler Can Actually Optimize (Mike Acton)
http://gdcvault.com/play/1021866/Code-Clinic-2015-How-to
| ; This code is hereby released by its author (Per Vognsen) into the public domain. | |
| ; It's mostly a proof of concept though it was surprisingly usable for how simple it was to code. | |
| ; If you want to use it as a starting point for a more polished package, go right ahead. | |
| (require 'cl) | |
| (defstruct wm-window buffer (point 0) (start 0) (hscroll 0) dedicated) | |
| (defvar wm-windows) | |
| (defvar wm-windows-alist) |
| // The original author of this software is David M. Gay. | |
| // RAD modifications from here down to the copyright notice | |
| // Actual RAD version of this includes rrCore.h which does | |
| // (among other things) endianness detection - you'll have to | |
| // do that yourself. | |
| #include "dtoa.h" | |
| // Again, we normally use our own assert macros here. |