With -O0, the attached code prints:

> /usr/local/ghc/ghc-8.4.1.0/bin/ghc -O0 src/foo.hs; and ./src/foo
[1 of 1] Compiling Main             ( src/foo.hs, src/foo.o ) [Optimisation flags changed]
Linking src/foo ...
("exec",0)
("depth",0)
("exec",1)
("depth",0)

But with -O1, it prints:

> /usr/local/ghc/ghc-8.4.1.0/bin/ghc -O1 src/foo.hs; and ./src/foo
[1 of 1] Compiling Main             ( src/foo.hs, src/foo.o )
Linking src/foo ...
("depth",0)
("depth",0)

Reproduced with 8.4.1 and 8.6.2. Doesn't seem to happen under 8.2.0