[llvm] [LLVM][TableGen] Support type casts of nodes with multiple results (PR #109728)

[Matt Arsenault via llvm-commits]

================
@@ -2896,6 +2896,35 @@ TreePatternNodePtr TreePattern::ParseTreePattern(Init *TheInit,
     error("Pattern has unexpected init kind!");
     return nullptr;
   }
+
+  auto ParseCastOperand = [this](DagInit *Dag, StringRef OpName) {
+    if (Dag->getNumArgs() != 1)
+      error("Type cast only takes one operand!");
+
+    if (!OpName.empty())
+      error("Type cast should not have a name!");
+
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arsenm wrote:

Can you add tests for these error conditions? 

https://github.com/llvm/llvm-project/pull/109728