RFR: 8338158: Cleanup ShouldNotXXX uses in machnode.cpp

[Christian Hagedorn]

On Mon, 12 Aug 2024 07:23:57 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change to machnode.cpp to remove dead code following calls
> to ShouldNotReachHere() and ShouldNotCallThis().  This takes advantage of the
> availability and use of [[noreturn]] attributes on all supported platforms,
> and makes all uses of those functions in this file consistent in this respect.
> 
> As a side effect, this removes some -Wzero-as-null-pointer-constant warnings.
> 
> Testing: mach5 tier1

Looks good! Will you update `fatal()` uses separately?

There is, for example:
https://github.com/openjdk/jdk/blob/03204600c596214895ef86581eba9722f76d39b3/src/hotspot/share/ci/ciEnv.cpp#L851-L852

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20540#pullrequestreview-2232266040