[llvm] [GlobalISel] Support fixed vectors in constant-fold combines. (PR #220876)

[Yaxun Liu via llvm-commits]

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@@ -408,3 +408,127 @@ body:             |
     RET_ReallyLR implicit $s0
 
 ...
+---
+name:            add_vector
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yxsamliu wrote:

Could we add one negative vector test where a lane cannot be folded, such as division by zero or an undef lane? This would make sure the combine leaves the whole operation unchanged instead of partially folding it.

https://github.com/llvm/llvm-project/pull/220876