[llvm] Two DWARF variant part improvements (PR #138953)

[David Blaikie via llvm-commits]

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@@ -961,6 +961,43 @@ void DwarfUnit::addAnnotation(DIE &Buffer, DINodeArray Annotations) {
   }
 }
 
+void DwarfUnit::addDiscriminant(DIE &Variant, Constant *Discriminant,
+                                bool IsUnsigned) {
+  if (const auto *CI = dyn_cast_or_null<ConstantInt>(Discriminant)) {
+    addInt(Variant, dwarf::DW_AT_discr_value, CI->getValue(), IsUnsigned);
+  } else if (const auto *CA =
+                 dyn_cast_or_null<ConstantDataArray>(Discriminant)) {
+    // Must have an even number of operands.
+    unsigned NElems = CA->getNumElements();
+    if (NElems % 2 != 0) {
+      return;
+    }
+
+    DIEBlock *Block = new (DIEValueAllocator) DIEBlock;
+
+    const auto AddInt = [&](const APInt &Val) {
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dwblaikie wrote:

LLVM doesn't generally use top level `const` on locals. (distinct from const on references (locals or otherwise) which is recommended) - mostly I find it problematic because it's rarely, if ever, applied consistently (eg: `NElems` and `Block` are also not mutated in this scope, but aren't marked const, etc) & so makes it more confusing to read by raising questions about what the significance of some things being const and some not is.

(similarly with the APInts below)

https://github.com/llvm/llvm-project/pull/138953