What optimization to turn off in g++ -O1 so that there is no [optimized out]?

Question

MinGW

Building G++ in -O1 is faster than in -O0: compilation of one file and full linking takes 11 seconds instead of 18. However, the debugger writes <optimized out> for many variables
Which of the optimizations to disable (and whether it can be done at all) so that these < optimized out> was not, but to keep a fast build?

Answer 1

-fno-tree-* (generally, anything that starts with tree and goes into O1).
It is pointless to single out further, each of them does something small.
But don't include -fno-tree-copy-prop, it outputs a hell of a bunch of false alarms.
UPD. Currently, it's better to use the LLD linker, period. The project has grown, and the linking takes “whole” TWO seconds.