1. Retargeting Open64 to A RISC processor -- A Student’s Perspective Author: Huimin Cui Xiaobing Feng 2009.03 1

2. Motivation Retarget is of significance for Open64 –Good retarget-ability brings more targets –more targets support brings more user. But there is no detailed manual –To show how to retarget step by step, to let even a green-hand can do the porting. –To give an overview of the performance just after retarget done. 2

3. Retarget Procedure Summarized a detailed procedure for future retarget –File creation order –Building order –Listed all the files that require modification –How to fix up some critical files 3

4. Retarget Procedure —our methodology(1) 1st step –Verify basic compiler issues, C Front-end IR transformation Code generation Simple Library Function Call –Naïve HelloWorld 4

5. Retarget Procedure —our methodology(2) 2nd step –Verify ABI/CFlow –Variations of HelloWorld Change Data types of parameters Add control-flow: branch & loop 3rd step –Verify optimization FRAMEWORK –-O0, -O2, -O3

6. Retarget Procedure —our methodology(3) 4th step –Further verify CG/optimizations/multiple procedures –Stanford benchmark, -O0 to –O3 5th step –Verify c++ FE/loop optimizations –Abstraction penalty benchmark, -O0 to –O3 6

7. Retarget Procedure—some points In most cases, it’s easier to tailor the files from existing ones Make the compiler work, then make it perform Use debugging tools of isolation/tracing/ dumping 7

8. Discussion—Easy of Retarget Took a student 2 months Dealt with –ISA –ABI –Code Generation –Some machine-dependent functions Passed the benchmarks, (-O0 to –O3) –Stanford Benchmark –Abstraction Penalty Benchmark –Some applications from CPU2000, bzip2 & mcf 8

9. Discussion—Performance (1) NO machine-dependent performance tuning after retarget. –competitive or better performance compared to a matured GCC-Mips compiler –obvious performance improvement from –O2 to – O3, especially for C++ programs with higher abstraction levels. 9

10. Discussion—Performance(2) Performance of abstraction penalty, -O2 and –O3 The higher, the better 10

11. Discussion—Performance(3) Performance of Stanford Benchmark The lower, the better 11

12. Discussion—Performance(4) Performance of bzip2 & mcf 12

13. Suggestions Can the flags distributed in multiple files be merged into one file? –Eg. Endianness Can some graphic tools be developed for view IR, flow, etc? 13

14. Summary A detailed retarget procedure (derived from Fred Chow’s document) –Shared our methodology Discussed two retargeting issues –Ease of retarget –Performance Some suggestions

15. Questions & Comments? please mail to: huimin.cui@gmail.comhuimin.cui@gmail.com 15