cmd/compile: use zero constants in comparisons where possible
Some integer comparisons with 1 and -1 can be rewritten as comparisons
with 0. For example, x < 1 is equivalent to x <= 0. This is an
advantageous transformation on riscv64 because comparisons with zero
do not require a constant to be loaded into a register. Other
architectures will likely benefit too and the transformation is
relatively benign on architectures that do not benefit.
Change-Id: I2ce9821dd7605a660eb71d76e83a61f9bae1bf25
Reviewed-on: https://go-review.googlesource.com/c/go/+/350831 Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Munday <mike.munday@lowrisc.org>
TryBot-Result: Gopher Robot <gobot@golang.org>