Re: gcc spectre stuff for netbsd-8

[maya%netbsd.org@localhost]

sorry for being terse, I'm not very knowledgeable about GCC/x86 but
applied it to our copy of GCC.

what it should be adding

Add -mindirect-branch-register to force indirect branch via register.
This is implemented by disabling patterns of indirect branch via memory,
similar to TARGET_X32.
https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00427.html

Add -mindirect-branch= option to convert indirect call and jump to call
and return thunks.  The default is 'keep', which keeps indirect call and
jump unmodified.  'thunk' converts indirect call and jump to call and
return thunk.  'thunk-inline' converts indirect call and jump to inlined
call and return thunk.  'thunk-extern' converts indirect call and jump to
external call and return thunk provided in a separate object file.  You
can control this behavior for a specific function by using the function
attribute indirect_branch.
https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00424.html

Add -mfunction-return= option to convert function return to call and
return thunks.  The default is 'keep', which keeps function return
unmodified.  'thunk' converts function return to call and return thunk.
'thunk-inline' converts function return to inlined call and return thunk.  'thunk-extern' converts function return to external call and return
thunk provided in a separate object file.  You can control this behavior
for a specific function by using the function attribute function_return.
https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00426.html