[llvm] [GlobalISel] Add G_CONCAT_VECTOR handling in computeNumSignBits (PR #142355)

[David Green via llvm-commits]

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@@ -1958,6 +1958,27 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
     }
     break;
   }
+  case TargetOpcode::G_CONCAT_VECTORS: {
+    if (MRI.getType(MI.getOperand(0).getReg()).isScalableVector())
+      break;
+    FirstAnswer = std::numeric_limits<unsigned>::max();
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davemgreen wrote:

I think this can use `FirstAnswer = TyBits;`

https://github.com/llvm/llvm-project/pull/142355