On 05/01/18 16:41, Martok wrote:
is it possible that the register allocation on x86_64 is a bit inefficient? No matter the optimization settings, I can never get FPC to use more than the rax and rdx registers. Especially $Optimization REGVAR does nothing (not even for loop variables). Instead, two nested loops are enough to get FPC to constantly do memory load/stores on the loop variables. If an assembler block is marked as using ['rdx', 'rax'] (i.e.: rdtsc), instead of using some other general-purpose registers, FPC stores them to memory before and reloads after the block. That doesn't seem very efficient...
regvars have always been disabled for routines that contain assembler blocks (on all architectures). Sometimes the compiler temporarily uses registers for other purposes over a longer period, which is why marking the used registers is still required.
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