[llvm] [GlobalISel][AArch64] AArch64O0PreLegalizerCombiner: Disable fixed-point iteration (PR #94291)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

For -O0, we use a special group of combines:
https://github.com/llvm/llvm-project/blob/e325e2e5928d4893bedee2d4bbb7d71cc855c67a/llvm/include/llvm/Target/GlobalISel/Combine.td#L1813

Is the one round vs fixed-point iteration issue limited to the -O0 combiner or is it a general issue of our combiners?

One advertisement of the Gisel combiner was that it could write a JSON file to the disk after a run. It would contain insights about which combines hit, which are nice to have, and compile time statistics.

https://github.com/llvm/llvm-project/pull/94291