[clang] [CIR] Upstream Cast kinds for ComplexType (PR #149717)

[Henrich Lauko via cfe-commits]

================
@@ -24,11 +25,118 @@ struct LoweringPreparePass : public LoweringPrepareBase<LoweringPreparePass> {
   void runOnOperation() override;
 
   void runOnOp(mlir::Operation *op);
+  void lowerCastOp(cir::CastOp op);
   void lowerUnaryOp(cir::UnaryOp op);
 };
 
 } // namespace
 
+static mlir::Value lowerScalarToComplexCast(MLIRContext &ctx, CastOp op) {
+  CIRBaseBuilderTy builder(ctx);
+  builder.setInsertionPoint(op);
+
+  mlir::Value src = op.getSrc();
+  mlir::Value imag = builder.getNullValue(src.getType(), op.getLoc());
+  return builder.createComplexCreate(op.getLoc(), src, imag);
+}
+
+static mlir::Value lowerComplexToScalarCast(MLIRContext &ctx, CastOp op) {
+  CIRBaseBuilderTy builder(ctx);
+  builder.setInsertionPoint(op);
+
+  mlir::Value src = op.getSrc();
+  if (!mlir::isa<cir::BoolType>(op.getType()))
+    return builder.createComplexReal(op.getLoc(), src);
+
+  // Complex cast to bool: (bool)(a+bi) => (bool)a || (bool)b
+  mlir::Value srcReal = builder.createComplexReal(op.getLoc(), src);
+  mlir::Value srcImag = builder.createComplexImag(op.getLoc(), src);
+
+  cir::CastKind elemToBoolKind;
+  if (op.getKind() == cir::CastKind::float_complex_to_bool)
+    elemToBoolKind = cir::CastKind::float_to_bool;
+  else if (op.getKind() == cir::CastKind::int_complex_to_bool)
+    elemToBoolKind = cir::CastKind::int_to_bool;
+  else
+    llvm_unreachable("invalid complex to bool cast kind");
----------------
xlauko wrote:

Same here, this does not even cover everything as switch where `lowerComplexToScalarCast` is used, i.e.:
`float_complex_to_real` and `int_complex_to_real`.

https://github.com/llvm/llvm-project/pull/149717