[Bug rtl-optimization/37571] Performance regression with -mtune=core2

2008-09-18 Thread hjl dot tools at gmail dot com
--- Comment #2 from hjl dot tools at gmail dot com 2008-09-18 16:10 --- (In reply to comment #1) > Root cause is that instruction length of fused jcc is set to 16, which prevent > the block from merging and copying. For some reason Core2 runs poorly with a > unmerged branch block under c

[Bug rtl-optimization/37571] Performance regression with -mtune=core2

2008-09-18 Thread Joey dot ye at intel dot com
--- Comment #1 from Joey dot ye at intel dot com 2008-09-18 16:01 --- Root cause is that instruction length of fused jcc is set to 16, which prevent the block from merging and copying. For some reason Core2 runs poorly with a unmerged branch block under certain circonstances. Following