[llvm] [GlobalISel] Combine G_MERGE_VALUES of x and undef (PR #113616)

[Amara Emerson via llvm-commits]

Thorsten =?utf-8?q?Schütt?= <schuett at gmail.com>,
Thorsten =?utf-8?q?Schütt?= <schuett at gmail.com>
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In-Reply-To: <llvm.org/llvm/llvm-project/pull/113616 at github.com>


aemerson wrote:

> All the wins are gone. Maybe, we are exploiting Zext and the known zero upper bits better.

That suggests we're solving the wrong problem. It's usually better to find a particular example you're trying to optimize and work backwards, to see what things are missing. 

https://github.com/llvm/llvm-project/pull/113616