GCC for Embedded Systems Ayal Zaks IBM Haifa Research Lab [email protected] http://www.haifa.il.ibm.com/dept/svt/code_compiler.html

IBM Haifa Research Lab

IBM Haifa Research Lab

GCC for Embedded Systems – Talk Goals


GCC for Embedded Systems – why GCC?
What (R&D) are we doing in GCC?
Where can you learn more?

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IBM Haifa Research Lab

GCC for Embedded Systems - Talk Layout 1. GCC – development: open community product of FSF 2. GCC – recent contributions from IBM Haifa  Vectorization (GCC 4.0)  Modulo scheduling (GCC 4.0)  Inter-Procedural constant propagation (GCC 4.1)  Data-layout optimizations (GCC 4.3) 3. GCC – performance for embedded: EEMBC 4. GCC – research: HiPEAC

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IBM Haifa Research Lab

GCC development – Mission Statement (from http://gcc.gnu.org/gccmission.html)

GCC development is a part of the GNU Project, aiming to improve the compiler used in the GNU system including the GNU/Linux® variant. The GCC development effort uses an open development environment and supports many other platforms in order to foster a world-class optimizing compiler, to attract a larger team of developers, to ensure that GCC and the GNU system work on multiple architectures and diverse environments, and to more thoroughly test and extend the features of GCC.

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IBM Haifa Research Lab

GNU Compiler Collection Advantages
Consistent across large number of targets (target is architecture plus operating system)
Very good warnings aid porting to new targets
Free software project:  licenses protect GCC as free software while allowing users to build proprietary software  doesn't depend on any one organization  developers have deep commitment to GCC  many choices for commercial support
Continuous improvement

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IBM Haifa Research Lab

Computer Architectures
Aspects of support  instructions, registers, memory  CPU tuning parameters
Architectures GCC supports 68HC11 68HC12 Alpha ARM AVR Blackfin C4x D30V FR-30 IA-32 IPF (IA-64) IQ2000 M68000 M88000 MCORE MN10300 PA-RISC PowerPC® S/390® SH SPARC V850 VAX Xscale Cell 6

AMD64 ARC CRIS CRX FR-V H8/300 M32C M32R MIPS MMIX PowerPC64 ROMP SPARC-V9 Stormy16 Xtensa z/Architecture™

IBM Haifa Research Lab

GCC – GNU Compiler Collection
Free Software Foundation (FSF)
2.3 million lines of code, 20 years of development (since 1987)
Multiple programming languages  C, C++, Objective-C, Ada, Java, Fortran
Multiplatform: Multiple target processors and operating systems  IBM eServers, RISC, embedded, ... (over 30 architectures!)  Linux, Unix, Windows, OS/X, embedded, ...
GCC is de-facto standard in the Linux eco-system

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IBM Haifa Research Lab

GCC – Development Process
Legal Issues Copyright held by the FSF (assignments required!) Licensed under the GPL


Who’s involved Volunteers Academia Linux distros RedHat, Novell/SUSE

IBM IBM LTC Haifa Lab IBM Research Vendors: CodeSourcery, ARM, AdaCore, more 8

IBM Haifa Research Lab

GCC for Embedded Systems - Talk Layout 1. GCC – development: product of Free Software Foundation community 2. GCC – recent contributions from IBM Haifa  Vectorization (GCC 4.0)  Modulo scheduling (GCC 4.0)  Inter-Procedural constant propagation (GCC 4.1)  Data-layout optimizations (GCC 4.3) 3. GCC – performance for embedded: EEMBC 4. GCC – research: HiPEAC

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IBM Haifa Research Lab

(http://www.gccsummit.org/2004/speakers.php) 10

IBM Haifa Research Lab

Programming for Vector Machines
Proliferation of SIMD (Single Instruction Multiple Data) model  MMX/SSE, Altivec
Communications, Video, Gaming
Fortran90 a[0:N] = b[0:N] + c[0:N];
Intrinsics vector float vb = vec_load (0, ptr_b); vector float vc = vec_load (0, ptr_c); vector float va = vec_add (vb, vc); vec_store (va, 0, ptr_a);
Autovectorization: Automatically transform serial code to vector code by the compiler. 11

IBM Haifa Research Lab

Vectorization


original serial loop: for(i=0; i>8 ); }


SPEC gzip – 9% improvement for (n = 0; n < SIZE; n++) { m = head[n]; head[n] = (m >= WSIZE ? m-WSIZE : 0); }

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lvx v0,r3,r2 vsubuhs v0,v0,v1 stvx v0,r3,r2 addi r2,r2,16 bdnz L2

IBM Haifa Research Lab

GCC Developers’ Summit 2005 (http://www.gccsummit.org/2005/speakers.php)

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IBM Haifa Research Lab

GCC Developers’ Summit 2006 (http://www.gccsummit.org/2006/speakers.php)

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IBM Haifa Research Lab

GCC for Embedded Systems - Talk Layout 1. GCC – development: product of Free Software Foundation community 2. GCC – recent contributions from IBM Haifa  Vectorization (GCC 4.0)  Modulo scheduling (GCC 4.0)  Inter-Procedural constant propagation (GCC 4.1)  Data-layout optimizations (GCC 4.3) 3. GCC – performance for embedded: EEMBC 4. GCC – research: HiPEAC

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IBM Haifa Research Lab

EEMBC Reports Record-Breaking Telecom Benchmark Scores for IBM PowerPC 970FX 2-GHz Processor “EL DORADO HILLS, Calif.—Aug. 21, 2006—The Embedded Microprocessor Benchmark Consortium today

announced certified EEMBC benchmark scores for the IBM PowerPC 970FX which set a new record for embedded processors tested against the consortium’s TeleBench™ telecommunications benchmark suite.

The IBM PowerPC 970FX, clocked at 2 GHz and using the GCC auto-vectorization compiler, with full-fury optimizations for Vector/SIMD Multimedia Extension Technology, achieved a score of 1058.7 Telemarks. In outof-the-box tests, the PowerPC 970FX achieved a score of 141.8 Telemarks, a 182% improvement over a previous record-setting score for the same device obtained with a different compiler. ... "High-end processors are being used in more embedded products than ever, and OEMs are looking for benchmark scores that offer a more application-specific indication of performance than traditional server benchmarks," said Markus Levy, EEMBC president. "By publishing these TeleBench scores for its PowerPC 970FX, IBM is showing its commitment to providing customers with valuable, trustworthy information on processor performance. Beyond delivering a realistic picture of how its device will perform in communications applications, the scores also represent a convincing indication of the performance advantages provided by vector processing in general.“ For this new round of PowerPC 970FX benchmark tests, and in accordance with EEMBC rules for optimization, IBM Research improved the GCC auto-vectorization compiler and IBM's Power Architecture Performance Team modified the EEMBC benchmark source code to use the VMX instructions documented in the PowerPC Microprocessor Family: Vector/SIMD Multimedia Extension Technology Programming Environments Manual. … Detailed score reports for the PowerPC 970FX are available free on the EEMBC web site at www.eembc.org.” (taken from: http://www.eembc.org/Press/PressRelease/060821.htm)

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IBM Haifa Research Lab

EEMBC: The Embedded Microprocessor Benchmark Consortium (http://www.eembc.org)

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IBM Haifa Research Lab

GCC for Embedded Systems - Talk Layout 1. GCC – development: product of Free Software Foundation community 2. GCC – recent contributions from IBM Haifa  Vectorization (GCC 4.0)  Modulo scheduling (GCC 4.0)  Inter-Procedural constant propagation (GCC 4.1)  Data-layout optimizations (GCC 4.3) 3. GCC – performance for embedded: EEMBC 4. GCC – research: HiPEAC

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IBM Haifa Research Lab

HiPEAC (www.hipeac.net)

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IBM Haifa Research Lab

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IBM Haifa Research Lab

References
GCC on the Free Software Foundation website: gcc.gnu.org (plus wiki)
www.gccsummit.org (including paper proceedings)
HiPEAC GCC Tutorials: http://www.hipeac.net/gcc-tutorial

Recent Academic Papers
"Auto-Vectorization of Interleaved Data for SIMD", Dorit Nuzman, Ira Rosen, and Ayal Zaks, PLDI, June 12-14, 2006, Ottawa, Canada
"Multi-platform Auto-vectorization", Dorit Nuzman and Richard Henderson, CGO4, March 26-29, 2006, Manhattan, New York
Thread-level speculation: PPoPP’06 [Liu et al.] and ICS’05 [Renau et al.]
Induction variable recognition: HiPEAC’05 [Pop et al.]
LLVM - life-long adaptive optimization: CGO’04 [Lattner and Adve]
Generic programming (template metaprogramming and concepts): PoPL’06 [Dos Reis and Stroustrup]
“Contributions to the GNU Compiler Collection GCC”, IBM’s Systems Journal, issue on Open Source, volume 44, number 2, 2005

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IBM Haifa Research Lab

GCC for Embedded Systems – Talk Goals


GCC for Embedded Systems – why GCC?
What (R&D) are we doing in GCC?
Where can you learn more?

thanks !

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