Eliminate more comparisons on the H8 port
This patch fixes a minor code quality issue I found while testing LRA on the
H8. Specifically we have a peephole which converts a comparison of a memory
location against zero into a load + comparison which is actually more
efficient. This triggers when there are registers available at the right
point during peephole2.
If the load is not a mode dependent address we can actually do better by
realizing the load itself sets the proper flags and eliminate the comparison.
I may have expected this to happen when I wrote the original peephole2,
but cmpelim runs before peephole2, so clearly if we want to eliminate the
comparison we have to do it manually.
gcc/
* config/h8300/testcompare.md: Add peephole2 which uses a memory
load to set flags, thus eliminating a compare against zero.