For the interested, LLVM-MCA says this Iterations: 10000 Instructions: 100000 Total Cycles: 25011 Total uOps: 100000

For the interested, LLVM-MCA says this Iterations: 10000 Instructions: 100000 Total Cycles: 25011 Total uOps: 100000 Dispatch Width: 4 uOps Per Cycle: 4.00 IPC: 4.00 Block RThroughput: 2.5 No resource or data dependency bottlenecks discovered. , which to me seems like 2.5 cycles per iteration (on Zen3). Tigerlake is a bit worse, at about 3 cycles per iteration, due to running more uOPs per iteration, by the looks of it. For the following loop core (extracted from `clang -O3 -march=znver3`, using trunk (5a8d5a2859d9bb056083b343588a2d87622e76a2)): .LBB5_2: # =>This Inner Loop Header: Depth=1 mov rdx, r11 add r11, r8 mulx rdx, rax, r9 xor rdx, rax mulx rdx, rax, r10 xor rdx, rax mov qword ptr [rdi + 8*rcx], rdx add rcx, 2 cmp rcx, rsi jb .LBB5_2