Browsing by Author "Waterman, Todd"
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Item Adaptive compilation and inlining(2006) Waterman, Todd; Cooper, Keith D.Adaptive compilation uses a feedback-driven process to leverage additional compilation time into improved executable performance. Previous work on adaptive compilation has demonstrated its benefit at an inter-optimization level. This dissertation investigates the ability of adaptive techniques to improve the performance of individual compiler optimizations. We first examine the ability to use adaptive compilation with current commercial compilers. We use adaptive techniques to find good blocking sizes with the MIPSpro compiler. However, we also observe that current compilers are poorly parameterized for adaptive compilation. We then construct an adaptive inlining system that demonstrates the potential of adaptive compilation to improve individual optimizations. We design the inliner to accept condition strings that determine which call sites are inlined. We develop an adaptive controller for the inliner based on a detailed understanding of the search space that the condition strings provide. Our adaptive inlining system consistently finds good sets of inlining decisions and outperforms static techniques. In addition, we demonstrate the inability of static techniques to provide a universal inlining solution and the necessity of adaptive inlining. Adaptive inlining demonstrates the capacity of adaptive compilation to improve the performance of a single, carefully designed optimization.Item Building a Control-flow Graph from Scheduled Assembly Code(2002-02-01) Cooper, Keith D.; Harvey, Timothy J.; Waterman, ToddA variety of applications have arisen where it is worthwhile to apply code optimizations directly to the machine code (or assembly code) produced by a compiler. These include link-time whole-program analysis and optimization, code compression, binary- to-binary translation, and bit-transition reduction (for power). Many, if not most, optimizations assume the presence of a control-flow graph (cfg). Compiled, scheduled code has properties that can make cfg construction more complex than it is inside a typical compiler. In this paper, we examine the problems of scheduled code on architectures that have multiple delay slots. In particular, if branch delay slots contain other branches, the classic algorithms for building a cfg produce incorrect results. We explain the problem using two simple examples. We then present an algorithm for building correct cfgs from scheduled assembly code that includes branches in branch-delay slots. The algorithm works by building an approximate cfg and then refining it to reflect the actions of delayed branches. If all branches have explicit targets, the complexity of the refining step is linear with respect to the number of branches in the code. Analysis of the kind presented in this paper is a necessary first step for any system that analyzes or translates compiled, assembly-level code. We have implemented this algorithm in our power-consumption experiments based on the TMS320C6200 architecture from Texas Instruments. The development of our algorithm was motivated by the output of TI’s compiler.Item Building Adaptive Compilers(2005-01-29) Almagor, L.; Cooper, Keith D.; Grosul, Alexander; Harvey, Timothy J.; Reeves, Steven W.; Subramanian, Devika; Torczon, Linda; Waterman, ToddTraditional compilers treat all programs equally -that is, they apply the same set of techniques to every program that they compile. Compilers that adapt their behavior to fit specific input programs can produce better results. This paper describes out experience building and using adaptive compilers. It presents experimental evidence to show two problems for which adaptive behavior can lead to better results: choosing compilation orders and choosing block sizes. It present data from experimental characterizations of the search spaces in which these adaptive systems operate and describes search algorithms that successfully operate in these spaces. Building these systems has taught us a number of lessons about the construction of modular and reconfigurable compilers. The paper describes some of the problems that we encountered and the solutions that we adopted. It also outlines a number of fertile areas for future research in adaptive compilation.Item Compilation Order Matters: Exploring the Structure of the Space of Compilation Sequences Using Randomized Search Algorithms(2004-06-18) Almagor, L.; Cooper, Keith D.; Grosul, Alexander; Harvey, Timothy J.; Reeves, Steven W.; Subramanian, Devika; Torczon, Linda; Waterman, ToddMost modern compilers operate by applying a fixed sequence of code optimizations, called a compilation sequence, to all programs. Compiler writers determine a small set of good, general-purpose, compilation sequences by extensive hand-tuning over particular benchmarks. The compilation sequence makes a significant difference in the quality of the generated code; in particular, we know that a single universal compilation sequence does not produce the best results over all programs. Three questions arise in customizing compilation sequences: (1) What is the incremental benefit of using a customized sequence instead of a universal sequence? (2) What is the average computational cost of constructing a customized sequence? (3) When does the benefit exceed the cost? We present one of the first empirically derived cost-benefit tradeoff curves for custom compilation sequences. These curves are for two randomized sampling algorithms: descent with randomized restarts and genetic algorithms. They demonstrate the dominance of these two methods over simple random sampling in sequence spaces where the probability of finding a good sequence is very low. Further, these curves allow compilers to decide whether custom sequence generation is worthwhile, by explicitly relating the computational effort required to obtain a program-specific sequence to the incremental improvement in quality of code generated by that sequence.