cmd/compile: internal compiler error: panic during rewrite tern with GOEXPERIMENT=simd [1.26 backport]

[gopherbot]

@dr2chase requested issue #77582 to be considered for backport to the next 1.26 minor release.

@gopherbot please open a backport issue to 1.26.

This is not a regression because it is a new feature (and an experiment), but we want people to try it out.

[gopherbot]

Change https://go.dev/cl/748540 mentions this issue: [release-branch.go1.26] cmd/compile: avoid panic in ternary rewrite on checked instructions

[dmitshur]

@dr2chase This backport issue is still open but without CherryPickApproved nor CherryPickCandidate label. Should this go back to approved but with CL 749241 as the new CL to backport? Or back to candidate so to be reviewed again next time?

[dr2chase]

I am happy to have it approved and the new CL as the one to backport, but given that it was my CL it seemed inappropriate for me to unilaterally make that decision, plus I was backed up with all the other, earlier and higher-visibility backported bugs. So, next dot release is fine with me.

[gopherbot]

Change https://go.dev/cl/750860 mentions this issue: [release-branch.go1.26] cmd/compile: ternary rewrite of rewrite should skip, not panic