On 04/05/2021 17:22, Eric Botcazou wrote:
A quick look through the code suggests it's being used for thumb1 code
gen to try to reproduce the traditional CC0 type behaviour of
eliminating redundant compare operations when you have sequences such as
cmp a, b
b<cond1> d1
cmp a, b
b<cond2> d2
The second compare operation can be eliminated.
It might be possible to eliminate this another way by reworking the
thumb1 codegen to expose the condition codes after register allocation
has completed (much like x86 does these days), but that would be quite a
lot of work right now. I don't know if such splitting would directly
lead to the ability to remove the redundant compares - it might need a
new pass to spot them.
Do you mean in addition to the existing pass_compare_elim_after_reload?
No, sounds like that would do the job. :)
R.
