[llvm] [GlobalISel] Rewrite binop_left_to_zero using MIR Patterns (PR #177924)

[Matt Arsenault via llvm-commits]

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@@ -17,3 +17,122 @@ body:             |
     $x10 = COPY %3(s64)
     PseudoRET implicit $x10
 ...
+
+---
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arsenm wrote:

I would hope these already had test coverage 

https://github.com/llvm/llvm-project/pull/177924