Deep

Conditional branches have traditionally been a performance bottleneck for most processors. The high frequency of branches in code coupled with expensive pipeline flushes on mispredictions make branches expensive instructions worth optimizing. Conditional branches have historically inhibited compilers from applying optimizations across basic block boundaries due to the forks in control flow that they introduce. This thesis describes a systematic way of generating paths (traces) of branch-free code at compile time by decomposing branching and verification operations to eliminate the dependence of a branch on its preceding compare instruction. This explicit decomposition allows us to move comparison instructions past branches and to merge pre and post branch code. These paths generated at compile time can potentially provide additional opportunities for conventional optimizations such as common subexpression elimination, dead assignment elimination and instruction selection. Moreover, this thesis describes a way of coalescing multiple branch instructions within innermost loops to produce longer basic blocks to provide additional optimization opportunities.