search for: lsr'd

> > I realize this is a micro-op saving a single cycle. But this reduces the instruction count, one less > instr to decode in a potentially hot path. If this all makes sense, and seems like a reasonable addition > to llvm, would it make sense to implement this as a supplemental LSR formula, or as a separate pass? This seems reasonable to me so long as rbx has no other uses that would complicate the problem; I’m not sure how much this occurs in hot code (a loop with an induction variable that isn’t used in the loop), but if it does, I don’t see why not. As a side note, in a...

...ing to implement a minor loop strength reduction optimization for targets that support compare and jump fusion, specifically TTI::canMacroFuseCmp(). My approach might be wrong; however, I am soliciting the idea for feedback, so that I can implement this correctly. My plan is to add a Supplemental LSR formula to LoopStrengthReduce.cpp that optimizes the following case, but perhaps this should stand alone as its own pass: // Example which can be optimized via cmp/jmp fusion. // clang -O3 -S test.c extern void g(int); void f(int *p, long long n) { do { g(*p++); } while (--n); }...