[clang] [CIR] Upstream new SetBitfieldOp for handling C and C++ struct bitfields (PR #147609)

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -2384,6 +2385,82 @@ mlir::LogicalResult CIRToLLVMComplexImagOpLowering::matchAndRewrite(
   return mlir::success();
 }
 
+mlir::LogicalResult CIRToLLVMSetBitfieldOpLowering::matchAndRewrite(
+    cir::SetBitfieldOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  mlir::OpBuilder::InsertionGuard guard(rewriter);
+  rewriter.setInsertionPoint(op);
+
+  cir::BitfieldInfoAttr info = op.getBitfieldInfo();
+  uint64_t size = info.getSize();
+  uint64_t offset = info.getOffset();
+  mlir::Type storageType = info.getStorageType();
+  mlir::MLIRContext *context = storageType.getContext();
+
+  unsigned storageSize = 0;
+
+  mlir::IntegerType intType =
----------------
bcardosolopes wrote:

This pattern happened in a recent PR, is it worth having a shared helper for getting this integer type?

https://github.com/llvm/llvm-project/pull/147609