Hi, +(simplify + (convert + (rshift + (mult
> is the outer convert really necessary? That is, if we change > the simplification result to Indeed that should be "convert?" to make it optional. > Is the Hamming weight popcount > faster than the libgcc table-based approach? I wonder if we really > need to restrict this conversion to the case where the target > has an expander. Well libgcc uses the exact same sequence (not a table): objdump -d ./aarch64-unknown-linux-gnu/libgcc/_popcountsi2.o 0000000000000000 <__popcountdi2>: 0: d341fc01 lsr x1, x0, #1 4: b200c3e3 mov x3, #0x101010101010101 // #72340172838076673 8: 9200f021 and x1, x1, #0x5555555555555555 c: cb010001 sub x1, x0, x1 10: 9200e422 and x2, x1, #0x3333333333333333 14: d342fc21 lsr x1, x1, #2 18: 9200e421 and x1, x1, #0x3333333333333333 1c: 8b010041 add x1, x2, x1 20: 8b411021 add x1, x1, x1, lsr #4 24: 9200cc20 and x0, x1, #0xf0f0f0f0f0f0f0f 28: 9b037c00 mul x0, x0, x3 2c: d378fc00 lsr x0, x0, #56 30: d65f03c0 ret So if you don't check for an expander you get an endless loop in libgcc since the makefile doesn't appear to use -fno-builtin anywhere... Wilco
