Use a fast path for column width computation for ascii characters. Especially
relevant for llvm-objdump.
before:
% time ./bin/llvm-objdump -D -j .text /lib/libc.so.6 >/dev/null
./bin/llvm-objdump -D -j .text /lib/libc.so.6 > /dev/null 0.75s user 0.01s system 99% cpu 0.757 total
after:
% time ./bin/llvm-objdump -D -j .text /lib/libc.so.6 >/dev/null
./bin/llvm-objdump -D -j .text /lib/libc.so.6 > /dev/null 0.37s user 0.01s system 99% cpu 0.378 total
Differential Revision: https://reviews.llvm.org/D92180
8db0e1abee