It is fairly easy to reuse the placement of block RAM macros and DSP macros. Reusing this placement helps to reduce the variability in results from one netlist revision to the next. These primitives generally have stable names. The placement is usually easy to maintain. Some placement directives result in better block RAM and DSP macro placement than others. You can try applying this improved macro placement from one placer run to others using different placer directives to improve QoR. Following is a simple Tcl script that saves block RAM placement into an XDC file.
set_property IS_LOC_FIXED 1 \
[get_cells -hier -filter {PRIMITIVE_TYPE =~ BLOCKRAM.*.*}]
write_xdc bram_loc.xdc -exclude_timing
You can edit the bram_loc.xdc file to only keep block RAM location constraints and apply it for your consecutive runs.