CellPerformance
All things related to getting the best performance from your Cell Broadband Engine™ (CBE) processor.
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Articles
Cross-compiling for PS3 Linux
n this article, I will detail the basic steps I used to get started building on a host PC and running on the PS3.

Unaligned scalar load and store on the SPU
An example of unaligned loads and stores on the SPU. The solution to this problem is to remember that the SPU does not have a scalar instruction set or access local memory in anything except 16 bytes quadwords.

atan2 on SPU
A branch-free implementation of atan2 vector floats for the SPU.

Branch-free implementation of half-precision (16 bit) floating point
The goal of this project is serve as an example of developing some relatively complex operations completely without branches - a software implementation of half-precision floating point numbers.

Better Performance Through Branch Elimination
An introduction to branch penalties: Why it's a good idea to avoid branchy code.

Box Overlap
A look at a function to test for overlap between 3D boxes, and how to optimize it for the CBE.

A 4x4 Matrix Inverse
Study case about how to convert scalar code indo SIMD code for PPU and SPU using the matrix inverse as example.

Avoiding Microcoded Instructions On The PPU
Executing instructions from microcode can wreck havok on inner loop performance. Find out which instructions are microcoded and how to avoid them.

Choosing to Avoid Branches: A Small Altivec Example
An example of why less instructions doesn't always equal faster code.

More Techniques for Eliminating Branches
Some additional examples for eliminating integer and floating-point branches.

Programming with Branches, Patterns and Tips
GCC follows some straightforward rules that are useful to know when programming with branches.

Benefits to Branch Elimination
The fundamental principal behind branch elimination is that expressing a value as a simple function of its inputs (a single basic block) is often more efficient than selecting a result through a change in control flow (branching).

Background on Branching
A background in understanding how branches operate on the PPU and SPU.

Links
No Insider Info!
Although discussions on applying the Cell processor to game development are welcome here, do not ask for insider information related to Sony's Playstation 3.

The details of the hardware and development are covered by a non-disclosure agreement and under no conditions will confidential information be permitted on this site.

Playstation 3 developers are welcome to participate in the discussions but be aware that this is a publicly accessable site and information not available to the general public may not be disclosed.

Keep it clean so that we can continue to build on the community of Cell developers both inside and outside video game development.

Thank you for your cooperation,
Mike.
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VEC_ALL_GE
Mike Acton
April 26, 2006
Description
int vec_all_ge( arg1, arg2 )
The value 1 (ONE) is returned if every element of arg1 are greater than or equal to the corresponding element in arg2. Otherwise the value 0 (ZERO) is returned.
Header Files
On the PPU:
#include <altivec.h>
On the SPU:
#include <vmx2spu.h>
PPU Instruction Mapping
The intrinsic is mapped to the following instructions depending on the type of arg1 and arg2:
vector unsigned char | vcmpgtub. vector signed char | vcmpgtsb. vector unsigned short | vcmpgtuh. vector signed short | vcmpgtsh. vector unsigned int | vcmpgtuw. vector signed int | vcmpgtsw. vector float | vcmpgtfp.
The Condition Register (CR) is modified. Note that a penalty may be incurred due to CR dependencies.

Note that the return value will be retrieved into a fixed point register. Example Instruction Sequence:
unsigned short vec_all_gt( unsigned short a, unsigned short b ); vcmpgtuh. 2,3,2 mfcr 3 rlwinm 3,3,27,1
SPU Instruction Mapping
The intrinsic is mapped to the following instructions depending on the type of arg1 and arg2:
vector unsigned char | clgtb vector signed char | cgtb vector unsigned short | clgth vector signed short | cgth vector unsigned int | clgt vector signed int | clg vector float | fclg
Example Instruction Sequence:
unsigned short vec_all_gt( unsigned short a, unsigned short b ); clgth $5,$4,$3 gbh $2,$5 ceqi $3,$2,0 sfi $3,$3,0