diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index 79fa38784932..100910f1e391 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -5410,7 +5410,7 @@ def AtomicCmpXchg : CIR_Op<"atomic.cmp_xchg",
 }
 
 def MemScope_SingleThread : I32EnumAttrCase<"MemScope_SingleThread",
-                                            0, "single_thread">;
+                                            0, "singlethread">;
 def MemScope_System       : I32EnumAttrCase<"MemScope_System",
                                             1, "system">;
 
@@ -5435,7 +5435,8 @@ def AtomicFence : CIR_Op<"atomic.fence"> {
       - `__c11_atomic_signal_fence`
 
     Example:
-
+    cir.atomic.fence(sync_scope = system, ordering = seq_cst)
+    cir.atomic.fence(sync_scope = singlethread, ordering = seq_cst)
 
   }];
   let results = (outs);
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index 455f8d859533..e58da6d86b5c 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -19,6 +19,7 @@
 #include "mlir/Dialect/DLTI/DLTI.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/Dialect/LLVMIR/Transforms/Passes.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/Builders.h"
@@ -3189,9 +3190,10 @@ mlir::LLVM::AtomicOrdering getLLVMAtomicOrder(cir::MemOrder memo) {
   llvm_unreachable("shouldn't get here");
 }
 
-// mlir::LLVM::AtomicSyncScope getLLVMSyncScope(cir::MemScopeKind syncScope) {
-//
-// }
+llvm::StringRef getLLVMSyncScope(cir::MemScopeKind syncScope) {
+  return syncScope == cir::MemScopeKind::MemScope_SingleThread ? "singlethread"
+                                                               : "";
+}
 
 mlir::LogicalResult CIRToLLVMAtomicCmpXchgLowering::matchAndRewrite(
     cir::AtomicCmpXchg op, OpAdaptor adaptor,
@@ -3360,11 +3362,17 @@ mlir::LogicalResult CIRToLLVMAtomicFetchLowering::matchAndRewrite(
   return mlir::success();
 }
 
-// mlir::LogicalResult CIRToLLVMAtomicFenceLowering::matchAndRewrite(
-//     cir::AtomicFence op, OpAdaptor adaptor,
-//     mlir::ConversionPatternRewriter &rewriter) const {
-//   return mlir::success();
-// }
+mlir::LogicalResult CIRToLLVMAtomicFenceLowering::matchAndRewrite(
+    cir::AtomicFence op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  auto llvmOrder = getLLVMAtomicOrder(adaptor.getOrdering());
+  auto llvmSyncScope = getLLVMSyncScope(adaptor.getSyncScope());
+
+  rewriter.replaceOpWithNewOp<mlir::LLVM::FenceOp>(op, llvmOrder,
+                                                   llvmSyncScope);
+
+  return mlir::success();
+}
 
 mlir::LogicalResult CIRToLLVMByteswapOpLowering::matchAndRewrite(
     cir::ByteswapOp op, OpAdaptor adaptor,
@@ -4129,6 +4137,7 @@ void populateCIRToLLVMConversionPatterns(
       CIRToLLVMAtomicCmpXchgLowering,
       CIRToLLVMAtomicFetchLowering,
       CIRToLLVMAtomicXchgLowering,
+      CIRToLLVMAtomicFenceLowering,
       CIRToLLVMBaseClassAddrOpLowering,
       CIRToLLVMBinOpLowering,
       CIRToLLVMBinOpOverflowOpLowering,
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h
index da57785012d4..8fc736cfac81 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h
@@ -822,15 +822,15 @@ class CIRToLLVMAtomicFetchLowering
                   mlir::ConversionPatternRewriter &) const override;
 };
 
-// class CIRToLLVMAtomicFenceLowering
-//     : public mlir::OpConversionPattern<cir::AtomicFence> {
-// public:
-//   using mlir::OpConversionPattern<cir::AtomicFence>::OpConversionPattern;
-//
-//   mlir::LogicalResult
-//   matchAndRewrite(cir::AtomicFence op, OpAdaptor,
-//                   mlir::ConversionPatternRewriter &) const override;
-// };
+class CIRToLLVMAtomicFenceLowering
+    : public mlir::OpConversionPattern<cir::AtomicFence> {
+public:
+  using mlir::OpConversionPattern<cir::AtomicFence>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::AtomicFence op, OpAdaptor,
+                  mlir::ConversionPatternRewriter &) const override;
+};
 
 class CIRToLLVMByteswapOpLowering
     : public mlir::OpConversionPattern<cir::ByteswapOp> {
diff --git a/clang/test/CIR/CodeGen/atomic-thread-fence.c b/clang/test/CIR/CodeGen/atomic-thread-fence.c
index cd97e3ecb93a..67164ab80432 100644
--- a/clang/test/CIR/CodeGen/atomic-thread-fence.c
+++ b/clang/test/CIR/CodeGen/atomic-thread-fence.c
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -triple aarch64-none-linux-android21 -fclangir -emit-cir %s -o %t.cir
 // RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
-// UN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll
-// UN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
 
 
 struct Data {
@@ -12,7 +12,7 @@ struct Data {
 typedef struct Data *DataPtr;
 
 void applyThreadFence() {
-  __atomic_thread_fence(5);
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
 }
 
 // CIR-LABEL: cir.func no_proto @applyThreadFence
@@ -20,80 +20,130 @@ void applyThreadFence() {
 // CIR:   cir.atomic.fence(sync_scope = system, ordering = seq_cst)
 // CIR:   cir.return
 
+// LLVM-LABEL: @applyThreadFence
+// LLVM:    fence seq_cst
+// LLVM:    ret void
+
 void applySignalFence() {
-  __atomic_signal_fence(5);
+  __atomic_signal_fence(__ATOMIC_SEQ_CST);
 }
 // CIR-LABEL: cir.func no_proto @applySignalFence
 // CIR:    %0 = cir.const #cir.int<5> : !s32i
-// CIR:    cir.atomic.fence(sync_scope = single_thread, ordering = seq_cst)
+// CIR:    cir.atomic.fence(sync_scope = singlethread, ordering = seq_cst)
 // CIR:    cir.return
 
+// LLVM-LABEL: @applySignalFence
+// LLVM:    fence syncscope("singlethread") seq_cst
+// LLVM:    ret void
+
 void modifyWithThreadFence(DataPtr d) {
-  __atomic_thread_fence(5);
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
   d->value = 42;
 }
 // CIR-LABEL: cir.func @modifyWithThreadFence
-// CIR:    %0 = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
-// CIR:    cir.store %arg0, %0 : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
+// CIR:    %[[DATA:.*]] = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
+// CIR:    cir.store %arg0, %[[DATA]] : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
 // CIR:    %1 = cir.const #cir.int<5> : !s32i
 // CIR:    cir.atomic.fence(sync_scope = system, ordering = seq_cst)
-// CIR:    %2 = cir.const #cir.int<42> : !s32i
-// CIR:    %3 = cir.load %0 : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
-// CIR:    %4 = cir.get_member %3[0] {name = "value"} : !cir.ptr<!ty_Data> -> !cir.ptr<!s32i>
-// CIR:    cir.store %2, %4 : !s32i, !cir.ptr<!s32i>
+// CIR:    %[[VAL_42:.*]] = cir.const #cir.int<42> : !s32i
+// CIR:    %[[LOAD_DATA:.*]] = cir.load %[[DATA]] : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
+// CIR:    %[[DATA_VALUE:.*]] = cir.get_member %[[LOAD_DATA]][0] {name = "value"} : !cir.ptr<!ty_Data> -> !cir.ptr<!s32i>
+// CIR:    cir.store %[[VAL_42]], %[[DATA_VALUE]] : !s32i, !cir.ptr<!s32i>
 // CIR:    cir.return
 
+// LLVM-LABEL: @modifyWithThreadFence
+// LLVM:    %[[DATA:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    store ptr %0, ptr %[[DATA]], align 8
+// LLVM:    fence seq_cst
+// LLVM:    %[[DATA_PTR:.*]] = load ptr, ptr %[[DATA]], align 8
+// LLVM:    %[[DATA_VALUE:.*]] = getelementptr %struct.Data, ptr %[[DATA_PTR]], i32 0, i32 0
+// LLVM:    store i32 42, ptr %[[DATA_VALUE]], align 4
+// LLVM:    ret void
+
 void modifyWithSignalFence(DataPtr d) {
-  __atomic_signal_fence(5);
+  __atomic_signal_fence(__ATOMIC_SEQ_CST);
   d->value = 24;
 }
 // CIR-LABEL: cir.func @modifyWithSignalFence
-// CIR:    %0 = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
-// CIR:    cir.store %arg0, %0 : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
+// CIR:    %[[DATA:.*]] = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
+// CIR:    cir.store %arg0, %[[DATA]] : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
 // CIR:    %1 = cir.const #cir.int<5> : !s32i
-// CIR:    cir.atomic.fence(sync_scope = single_thread, ordering = seq_cst)
-// CIR:    %2 = cir.const #cir.int<24> : !s32i
-// CIR:    %3 = cir.load %0 : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
-// CIR:    %4 = cir.get_member %3[0] {name = "value"} : !cir.ptr<!ty_Data> -> !cir.ptr<!s32i>
-// CIR:    cir.store %2, %4 : !s32i, !cir.ptr<!s32i>
+// CIR:    cir.atomic.fence(sync_scope = singlethread, ordering = seq_cst)
+// CIR:    %[[VAL_42:.*]] = cir.const #cir.int<24> : !s32i
+// CIR:    %[[LOAD_DATA:.*]] = cir.load %[[DATA]] : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
+// CIR:    %[[DATA_VALUE:.*]] = cir.get_member %[[LOAD_DATA]][0] {name = "value"} : !cir.ptr<!ty_Data> -> !cir.ptr<!s32i>
+// CIR:    cir.store %[[VAL_42]], %[[DATA_VALUE]] : !s32i, !cir.ptr<!s32i>
 // CIR:    cir.return
 
+// LLVM-LABEL: @modifyWithSignalFence
+// LLVM:    %[[DATA:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    store ptr %0, ptr %[[DATA]], align 8
+// LLVM:    fence syncscope("singlethread") seq_cst
+// LLVM:    %[[DATA_PTR:.*]] = load ptr, ptr %[[DATA]], align 8
+// LLVM:    %[[DATA_VALUE:.*]] = getelementptr %struct.Data, ptr %[[DATA_PTR]], i32 0, i32 0
+// LLVM:    store i32 24, ptr %[[DATA_VALUE]], align 4
+// LLVM:    ret void
+
 void loadWithThreadFence(DataPtr d) {
-  __atomic_thread_fence(5);
-  __atomic_load_n(&d->ptr, 5);
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+  __atomic_load_n(&d->ptr, __ATOMIC_SEQ_CST);
 }
 // CIR-LABEL: cir.func @loadWithThreadFence
-// CIR:    %0 = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
-// CIR:    %1 = cir.alloca !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>, ["atomic-temp"] {alignment = 8 : i64}
-// CIR:    cir.store %arg0, %0 : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
+// CIR:    %[[DATA:.*]] = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
+// CIR:    %[[ATOMIC_TEMP:.*]] = cir.alloca !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>, ["atomic-temp"] {alignment = 8 : i64}
+// CIR:    cir.store %arg0, %[[DATA]] : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
 // CIR:    %2 = cir.const #cir.int<5> : !s32i
 // CIR:    cir.atomic.fence(sync_scope = system, ordering = seq_cst)
-// CIR:    %3 = cir.load %0 : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
-// CIR:    %4 = cir.get_member %3[1] {name = "ptr"} : !cir.ptr<!ty_Data> -> !cir.ptr<!cir.ptr<!void>>
+// CIR:    %[[LOAD_DATA:.*]] = cir.load %[[DATA]] : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
+// CIR:    %[[DATA_VALUE:.*]] = cir.get_member %[[LOAD_DATA]][1] {name = "ptr"} : !cir.ptr<!ty_Data> -> !cir.ptr<!cir.ptr<!void>>
 // CIR:    %5 = cir.const #cir.int<5> : !s32i
-// CIR:    %6 = cir.cast(bitcast, %4 : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
-// CIR:    %7 = cir.load atomic(seq_cst) %6 : !cir.ptr<!u64i>, !u64i
-// CIR:    %8 = cir.cast(bitcast, %1 : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
-// CIR:    cir.store %7, %8 : !u64i, !cir.ptr<!u64i>
-// CIR:    %9 = cir.load %1 : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
+// CIR:    %[[CASTED_DATA_VALUE:.*]] = cir.cast(bitcast, %[[DATA_VALUE]] : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
+// CIR:    %[[ATOMIC_LOAD:.*]] = cir.load atomic(seq_cst) %[[CASTED_DATA_VALUE]] : !cir.ptr<!u64i>, !u64i
+// CIR:    %[[CASTED_ATOMIC_TEMP:.*]] = cir.cast(bitcast, %[[ATOMIC_TEMP]] : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
+// CIR:    cir.store %[[ATOMIC_LOAD]], %[[CASTED_ATOMIC_TEMP]] : !u64i, !cir.ptr<!u64i>
+// CIR:    %[[ATOMIC_LOAD_PTR:.*]] = cir.load %[[ATOMIC_TEMP]] : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
 // CIR:    cir.return
 
+// LLVM-LABEL: @loadWithThreadFence
+// LLVM:    %[[DATA:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    %[[DATA_TEMP:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    store ptr %0, ptr %[[DATA]], align 8
+// LLVM:    fence seq_cst
+// LLVM:    %[[DATA_PTR:.*]] = load ptr, ptr %2, align 8
+// LLVM:    %[[DATA_VALUE:.*]] = getelementptr %struct.Data, ptr %[[DATA_PTR]], i32 0, i32 1
+// LLVM:    %[[ATOMIC_LOAD:.*]] = load atomic i64, ptr %[[DATA_VALUE]] seq_cst, align 8
+// LLVM:    store i64 %[[ATOMIC_LOAD]], ptr %[[DATA_TEMP]], align 8
+// LLVM:    %[[DATA_TEMP_LOAD:.*]] = load ptr, ptr %[[DATA_TEMP]], align 8
+// LLVM:    ret void
+
 void loadWithSignalFence(DataPtr d) {
-  __atomic_signal_fence(5);
-  __atomic_load_n(&d->ptr, 5);
+  __atomic_signal_fence(__ATOMIC_SEQ_CST);
+  __atomic_load_n(&d->ptr, __ATOMIC_SEQ_CST);
 }
 // CIR-LABEL: cir.func @loadWithSignalFence
-// CIR:    %0 = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
-// CIR:    %1 = cir.alloca !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>, ["atomic-temp"] {alignment = 8 : i64}
-// CIR:    cir.store %arg0, %0 : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
+// CIR:    %[[DATA:.*]] = cir.alloca !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>, ["d", init] {alignment = 8 : i64}
+// CIR:    %[[ATOMIC_TEMP:.*]] = cir.alloca !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>, ["atomic-temp"] {alignment = 8 : i64}
+// CIR:    cir.store %arg0, %[[DATA]] : !cir.ptr<!ty_Data>, !cir.ptr<!cir.ptr<!ty_Data>>
 // CIR:    %2 = cir.const #cir.int<5> : !s32i
-// CIR:    cir.atomic.fence(sync_scope = single_thread, ordering = seq_cst)
-// CIR:    %3 = cir.load %0 : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
-// CIR:    %4 = cir.get_member %3[1] {name = "ptr"} : !cir.ptr<!ty_Data> -> !cir.ptr<!cir.ptr<!void>>
+// CIR:    cir.atomic.fence(sync_scope = singlethread, ordering = seq_cst)
+// CIR:    %[[LOAD_DATA:.*]] = cir.load %[[DATA]] : !cir.ptr<!cir.ptr<!ty_Data>>, !cir.ptr<!ty_Data>
+// CIR:    %[[DATA_PTR:.*]] = cir.get_member %[[LOAD_DATA]][1] {name = "ptr"} : !cir.ptr<!ty_Data> -> !cir.ptr<!cir.ptr<!void>>
 // CIR:    %5 = cir.const #cir.int<5> : !s32i
-// CIR:    %6 = cir.cast(bitcast, %4 : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
-// CIR:    %7 = cir.load atomic(seq_cst) %6 : !cir.ptr<!u64i>, !u64i
-// CIR:    %8 = cir.cast(bitcast, %1 : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
-// CIR:    cir.store %7, %8 : !u64i, !cir.ptr<!u64i>
-// CIR:    %9 = cir.load %1 : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
+// CIR:    %[[CASTED_DATA_PTR:.*]] = cir.cast(bitcast, %[[DATA_PTR]] : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
+// CIR:    %[[ATOMIC_LOAD:.*]] = cir.load atomic(seq_cst) %[[CASTED_DATA_PTR]] : !cir.ptr<!u64i>, !u64i
+// CIR:    %[[CASTED_ATOMIC_TEMP:.*]] = cir.cast(bitcast, %[[ATOMIC_TEMP]] : !cir.ptr<!cir.ptr<!void>>), !cir.ptr<!u64i>
+// CIR:    cir.store %[[ATOMIC_LOAD]], %[[CASTED_ATOMIC_TEMP]] : !u64i, !cir.ptr<!u64i>
+// CIR:    %[[LOAD_ATOMIC_TEMP:.*]] = cir.load %[[ATOMIC_TEMP]] : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
 // CIR:    cir.return
+
+// LLVM-LABEL: @loadWithSignalFence
+// LLVM:    %[[DATA:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    %[[DATA_TEMP:.*]] = alloca ptr, i64 1, align 8
+// LLVM:    store ptr %0, ptr %[[DATA]], align 8
+// LLVM:    fence syncscope("singlethread") seq_cst
+// LLVM:    %[[DATA_PTR:.*]] = load ptr, ptr %[[DATA]], align 8
+// LLVM:    %[[DATA_VALUE:.*]] = getelementptr %struct.Data, ptr %[[DATA_PTR]], i32 0, i32 1
+// LLVM:    %[[ATOMIC_LOAD:.*]] = load atomic i64, ptr %[[DATA_VALUE]] seq_cst, align 8
+// LLVM:    store i64 %[[ATOMIC_LOAD]], ptr %[[DATA_TEMP]], align 8
+// LLVM:    %[[DATA_TEMP_LOAD]] = load ptr, ptr %[[DATA_TEMP]], align 8
+// LLVM:    ret void