4 ms·

I dunno, I see the same issue in GCC, even at -Og. Both compilers will aggressively mark variables dead and reuse their (memory, registers) as soon as possible

• loeg 6y ago
  Yes, scope and liveness are not exactly the same. No, that does not mean the scoped value cannot be restored cheaply. DWARF can express the value of a variable in terms of expressions that do computations on other registers and/or access memory; it does not have to be as simplistic as "this value lives in this register for some period of time." Clang (and to a lesser extent, GCC) fail to do that for non-live, in-scope registers much of the time. Clang in particular just loses that metadata in many optimization passes.