IDEA: trace scheduling

• Compiler technique that schedules across several branches
• Packs operations from most-likely path (``trace'') into minimum no of inst words
• Using static branch prediction based on execution profiles
• In effect, compile-time speculative execution
• Misprediction penalty still large (though could speculate on both branches...)

Nasty practical problem:

• Instructions executed speculatively (moved across a branch) might cause page faults or FP exceptions

(Software pipelining is essentially the same idea applied to loops; see tutorial exercise) (H&P pp.296)