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diff --git a/docs/HistoricalNotes/2001-04-16-DynamicCompilation.txt b/docs/HistoricalNotes/2001-04-16-DynamicCompilation.txt deleted file mode 100644 index 5f7843a..0000000 --- a/docs/HistoricalNotes/2001-04-16-DynamicCompilation.txt +++ /dev/null @@ -1,49 +0,0 @@ -By Chris: - -LLVM has been designed with two primary goals in mind. First we strive to -enable the best possible division of labor between static and dynamic -compilers, and second, we need a flexible and powerful interface -between these two complementary stages of compilation. We feel that -providing a solution to these two goals will yield an excellent solution -to the performance problem faced by modern architectures and programming -languages. - -A key insight into current compiler and runtime systems is that a -compiler may fall in anywhere in a "continuum of compilation" to do its -job. On one side, scripting languages statically compile nothing and -dynamically compile (or equivalently, interpret) everything. On the far -other side, traditional static compilers process everything statically and -nothing dynamically. These approaches have typically been seen as a -tradeoff between performance and portability. On a deeper level, however, -there are two reasons that optimal system performance may be obtained by a -system somewhere in between these two extremes: Dynamic application -behavior and social constraints. - -From a technical perspective, pure static compilation cannot ever give -optimal performance in all cases, because applications have varying dynamic -behavior that the static compiler cannot take into consideration. Even -compilers that support profile guided optimization generate poor code in -the real world, because using such optimization tunes that application -to one particular usage pattern, whereas real programs (as opposed to -benchmarks) often have several different usage patterns. - -On a social level, static compilation is a very shortsighted solution to -the performance problem. Instruction set architectures (ISAs) continuously -evolve, and each implementation of an ISA (a processor) must choose a set -of tradeoffs that make sense in the market context that it is designed for. -With every new processor introduced, the vendor faces two fundamental -problems: First, there is a lag time between when a processor is introduced -to when compilers generate quality code for the architecture. Secondly, -even when compilers catch up to the new architecture there is often a large -body of legacy code that was compiled for previous generations and will -not or can not be upgraded. Thus a large percentage of code running on a -processor may be compiled quite sub-optimally for the current -characteristics of the dynamic execution environment. - -For these reasons, LLVM has been designed from the beginning as a long-term -solution to these problems. Its design allows the large body of platform -independent, static, program optimizations currently in compilers to be -reused unchanged in their current form. It also provides important static -type information to enable powerful dynamic and link time optimizations -to be performed quickly and efficiently. This combination enables an -increase in effective system performance for real world environments. |