cmd/compile: schedule values with no in-block uses later
When scheduling a block, deprioritize values whose results aren't used
until subsequent blocks.
For #58166, this has the effect of pushing the induction variable increment
to the end of the block, past all the other uses of the pre-incremented value.
Do this only with optimizations on. Debuggers have a preference for values
in source code order, which this CL can degrade.
Fixes #58166
Fixes #57976
Change-Id: I40d5885c661b142443c6d4702294c8abe8026c4f
Reviewed-on: https://go-review.googlesource.com/c/go/+/463751
Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>