Eric is right, but not for the right reasons. For starters, Apple's money is not the main driver of LLVM (In fact, publicly, Apple is not the #1 contributor anymore). Second, "but merely the fact that compiler technology has advanced significantly in ways that GCC is not well positioned to exploit. " is simply false In fact, that's exactly the problem for GCC: Compiler technology has not advanced roughly at all . GCC…
There are still plenty of open problems in compilers. For instance, writing a program to effectively use all four of my CPU cores is pretty tedious. It would be awfully nice if my compiler could automatically parallelize operations, do effective register allocation across cores, distribute data for best use of L1 cache, etc. Certainly researchers who are working on this sort of thing today are doing it in LLVM or som…
The rest (effective cache/register/op usage) is all subsumed by cost models for polyhedral loop transforms. See PLUTO (http://www.ece.lsu.edu/jxr/pluto/) and PLUTO+ (http://dl.acm.org/citation.cfm?id=2688512)