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

[Erich Keane via cfe-commits]

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@@ -321,9 +325,20 @@ void CIRGenFunction::emitStoreOfScalar(mlir::Value value, Address addr,
 
 mlir::Value CIRGenFunction::emitStoreThroughBitfieldLValue(RValue src,
                                                            LValue dst) {
-  assert(!cir::MissingFeatures::bitfields());
-  cgm.errorNYI("bitfields");
-  return {};
+
+  assert(!cir::MissingFeatures::armComputeVolatileBitfields());
+
+  const CIRGenBitFieldInfo &info = dst.getBitFieldInfo();
+  mlir::Type resLTy = convertTypeForMem(dst.getType());
+  Address ptr = dst.getBitFieldAddress();
+
+  const bool useVolatile = false;
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erichkeane wrote:

Can weput the MissingFeatures assert right next to this?

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