The default mapping rules for division-like operations (div/divfloor/
mod/modfloor) invoke subtractions which can get mapped to carry chains
in FPGA flows. Optimizations across carry chains are weak, so in
practice this ends up too costly compared to implementing the division
purely in soft logic.
For this reason arrange for `techmap.v` ignoring division operations
under `-D NODIV`, and use this mode in `synth_quicklogic` to avoid carry
chains for divisions.
Remove duplicate %.pmg -> %_pm.h pattern. One of the duplicates overrode
the other, and in some conditions there were build races as to whether
the target directory for the generated header would exist. Instead have
a single rule which is properly generalized.
Clean up the code up to Yosys standards. Drop detection of
QL_DSP2_MULTADD in io_regs since those cells can't be inferred with
the current flow anyway.
Uses the regex below to search (using vscode):
^\t\tlog\("(.{10,}(?<!\\n)|.{81,}\\n)"\);
Finds any log messages double indented (which help messages are)
and checks if *either* there are is no newline character at the end,
*or* the number of characters before the newline is more than 80.
