[clang] [CIR] Upstream Exception ThrowOp with subexpr (PR #161818)

[Andy Kaylor via cfe-commits]

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@@ -1544,6 +1545,60 @@ void CIRGenItaniumCXXABI::emitRethrow(CIRGenFunction &cgf, bool isNoReturn) {
   }
 }
 
+void CIRGenItaniumCXXABI::emitThrow(CIRGenFunction &cgf,
+                                    const CXXThrowExpr *e) {
+  // This differs a bit from LLVM codegen, CIR has native operations for some
+  // cxa functions, and defers allocation size computation, always pass the dtor
+  // symbol, etc. CIRGen also does not use getAllocateExceptionFn / getThrowFn.
+
+  // Now allocate the exception object.
+  CIRGenBuilderTy &builder = cgf.getBuilder();
+  QualType clangThrowType = e->getSubExpr()->getType();
+  cir::PointerType throwTy =
+      builder.getPointerTo(cgf.convertType(clangThrowType));
+  uint64_t typeSize =
+      cgf.getContext().getTypeSizeInChars(clangThrowType).getQuantity();
+  mlir::Location subExprLoc = cgf.getLoc(e->getSubExpr()->getSourceRange());
+
+  // Defer computing allocation size to some later lowering pass.
+  mlir::TypedValue<cir::PointerType> exceptionPtr =
+      cir::AllocExceptionOp::create(builder, subExprLoc, throwTy,
+                                    builder.getI64IntegerAttr(typeSize))
+          .getAddr();
+
+  // Build expression and store its result into exceptionPtr.
+  CharUnits exnAlign = cgf.getContext().getExnObjectAlignment();
+  cgf.emitAnyExprToExn(e->getSubExpr(), Address(exceptionPtr, exnAlign));
+
+  // Get the RTTI symbol address.
+  auto typeInfo = mlir::dyn_cast_if_present<cir::GlobalViewAttr>(
+      cgm.getAddrOfRTTIDescriptor(subExprLoc, clangThrowType,
+                                  /*forEH=*/true));
+  assert(typeInfo && "expected GlobalViewAttr typeinfo");
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andykaylor wrote:

Would changing `mlir::dyn_cast_if_present` to `mlir::cast` have the same effect as this assert?

https://github.com/llvm/llvm-project/pull/161818