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*# We can explicitly include SIMD instructions in a C program by using [[Inline Assembly Language|Inline Assembler]]. This is obviously architecture-specific, so it is important to use C preprocessor directives to include/exclude this code, and to use a generic C implementation on any platform for which you are not providing an inline assembler version.
*# ''C Intrinsics'' are function-like capabilities built into the C compiler. There is a group of intrinsics which provide access to SIMD instructions. However, the benefit of using these over inline assembler is debatable. SIMD intrinsics are not portable, and should be included with C preprocessor directives like inline assembler.
* [[Inline Assembly Language]]
* C Intrinsics
** C Intrinsics are function-like extensions to the C language. Although they look like functions, they are compiled inline, and they are used to provide access to features which are not provided by the C language itself. See the Resources section below for additional detail.
=== Week 5 - Class II ===
* [[SPO600 SIMD Lab]] (Lab 5)
=== Week 5 Resources ===
==== Auto-vectorization ====
* [https://gcc.gnu.org/projects/tree-ssa/vectorization.html Auto-Vectorization in GCC] - Main project page for the GCC auto-vectorizer.
* [http://locklessinc.com/articles/vectorize/ Auto-vectorization with gcc 4.7] - An excellent discussion of the capabilities and limitations of the GCC auto-vectorizer, intrinsics for providing hints to GCC, and other code pattern changes that can improve results. Note that there has been some improvement in the auto-vectorizer since this article was written. '''This article is strongly recommended.'''
* [https://software.intel.com/sites/default/files/8c/a9/CompilerAutovectorizationGuide.pdf Intel (Auto)Vectorization Tutorial] - this deals with the Intel compiler (ICC) but the general technical discussion is valid for other compilers such as gcc and llvm
==== Inline Assembly Language ====
* [[Inline Assembly Language]]
* [http://developer.arm.com ARM Developer Information Centre]
** [https://developer.arm.com/products/architecture/a-profile/docs/den0024/a ARM Cortex-A Series Programmer’s Guide for ARMv8-A]
* The ''short'' guide to the ARMv8 instruction set: [https://www.element14.com/community/servlet/JiveServlet/previewBody/41836-102-1-229511/ARM.Reference_Manual.pdf ARMv8 Instruction Set Overview] ("ARM ISA Overview")
* The ''long'' guide to the ARMv8 instruction set: [https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile ARM Architecture Reference Manual ARMv8, for ARMv8-A architecture profile] ("ARM ARM")
==== C Intrinsics - AArch64 SIMD ====
* [https://developer.arm.com/architectures/instruction-sets/simd-isas/neon/intrinsics ARM NEON Intrinsics Reference]
* [https://gcc.gnu.org/onlinedocs/gcc/ARM-C-Language-Extensions-_0028ACLE_0029.html GCC ARM C Language Extensions]
=== Week 5 Deliverables ===