[llvm] [GlobalIsel] Add G_SCMP and G_UCMP instructions (PR #98894)

[Michael Maitland via llvm-commits]

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@@ -1273,6 +1273,34 @@ class MachineIRBuilder {
                                 const SrcOp &Op0, const SrcOp &Op1,
                                 std::optional<unsigned> Flags = std::nullopt);
 
+  /// Build and insert a \p Res = G_SCMP \p Op0, \p Op1
+  ///
+  /// \pre setBasicBlock or setMI must have been called.
+
+  /// \pre \p Res must be a generic virtual register with scalar or
+  ///      vector type. Typically this starts as s2 or <N x s2>.
+  /// \pre \p Op0 and Op1 must be generic virtual registers with the
+  ///      same number of elements as \p Res. If \p Res is a scalar,
+  ///      \p Op0 must be a scalar.
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michaelmaitland wrote:

If Res is a scalar, does Op0 and Op1 need to have the same bitwidth?

https://github.com/llvm/llvm-project/pull/98894