Adding white space/newlines outside the function also affect the length of assembly.
On Tue, Feb 14, 2023 at 5:09 PM Owen Cook <owenthegame...@gmail.com> wrote: > Within "unrollOptimizations.c" compiled on a Ryzen 5 2600 using x86-64 gcc > 12.2 "-O2 -march=native" gives vastly different assembler results given > some scope things I have found. If the for loop iterator name is both int i > in each loop, gcc seemingly spreads arrayA and arrayB into one single XMM > register, name them differently and you get usages over XMM and YMM. > Additionally, white space seems to be a variable to this as well. you can > have the for loops one newline away from each other and this results in XMM > YMM, but put them together and you get XMM. Changing float* a to float* > const a (same goes for float* b) also changes these values. > > Godbolt equivalent for simplicity > https://godbolt.org/z/4xWrGoPaE >
