The speculative optimization of Example 16.5 could in principle be statically performed. Explain why a dynamic compiler might be able to do it more effectively. Perhaps the most common form of...

The speculative optimization of Example 16.5 could in principle be statically performed. Explain why a dynamic compiler might be able to do it more effectively. Perhaps the most common form of run-time instrumentation counts the the number of times that each basic block is executed. Since basic blocks are short, adding a load-increment-store instruction sequence to each block can have a significant impact on run time. We can improve performance by noting that certain blocks imply the execution of other blocks. In an if... then ... else construct, for example, execution of either the then part or the else part implies execution of the conditional test. If we’re smart, we won’t actually have to instrument the test. Describe a general technique to minimize the number of blocks that must be instrumented to allow a post-processor to obtain an accurate count for each block. (This is a difficult problem. For hints, see the paper by Larus and Ball [BL92].)