[clang] [clang][Interp] Implement integral->complex casts (PR #75590)

[Aaron Ballman via cfe-commits]

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@@ -283,6 +283,28 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
   case CK_ToVoid:
     return discard(SubExpr);
 
+  case CK_IntegralRealToComplex:
+  case CK_FloatingRealToComplex: {
+    // We're creating a complex value here, so we need to
+    // allocate storage for it.
+    if (!Initializing) {
+      std::optional<unsigned> LocalIndex =
+          allocateLocal(CE, /*IsExtended=*/true);
+      if (!LocalIndex)
+        return false;
+      if (!this->emitGetPtrLocal(*LocalIndex, CE))
+        return false;
+    }
+
+    if (!this->visitArrayElemInit(0, SubExpr))
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AaronBallman wrote:

Might as well add a comment as to why we zero init.

https://github.com/llvm/llvm-project/pull/75590