[clang] [CIR] Add cir.atomic.xchg to target lowering (PR #180744)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clangir

Author: Sirui Mu (Lancern)

<details>
<summary>Changes</summary>

This patch adds the `cir.atomic.xchg` operation to the TargetLowering pass. The synchronization scope attached to the operation will be canonicalized there.

---
Full diff: https://github.com/llvm/llvm-project/pull/180744.diff


2 Files Affected:

- (modified) clang/lib/CIR/Dialect/Transforms/TargetLowering.cpp (+1-1) 
- (modified) clang/test/CIR/CodeGen/atomic-scoped.c (+6-2) 


``````````diff
diff --git a/clang/lib/CIR/Dialect/Transforms/TargetLowering.cpp b/clang/lib/CIR/Dialect/Transforms/TargetLowering.cpp
index 656f29dab4e92..b542753072697 100644
--- a/clang/lib/CIR/Dialect/Transforms/TargetLowering.cpp
+++ b/clang/lib/CIR/Dialect/Transforms/TargetLowering.cpp
@@ -58,7 +58,7 @@ void TargetLoweringPass::runOnOperation() {
   }
 
   mod->walk([&](mlir::Operation *op) {
-    if (mlir::isa<cir::LoadOp, cir::StoreOp>(op))
+    if (mlir::isa<cir::LoadOp, cir::StoreOp, cir::AtomicXchgOp>(op))
       convertSyncScopeIfPresent(op, *lowerModule);
   });
 }
diff --git a/clang/test/CIR/CodeGen/atomic-scoped.c b/clang/test/CIR/CodeGen/atomic-scoped.c
index d34b95b9a305a..9caab232154af 100644
--- a/clang/test/CIR/CodeGen/atomic-scoped.c
+++ b/clang/test/CIR/CodeGen/atomic-scoped.c
@@ -87,11 +87,13 @@ void scoped_atomic_exchange(int *ptr, int *value, int *old) {
   // OGCG-LABEL: @scoped_atomic_exchange
 
   __scoped_atomic_exchange(ptr, value, old, __ATOMIC_RELAXED, __MEMORY_SCOPE_SINGLE);
-  // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(single_thread) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
+  // CIR-BEFORE-TL: cir.atomic.xchg relaxed syncscope(single_thread) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
+  // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // LLVM: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
   // OGCG: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
 
   __scoped_atomic_exchange(ptr, value, old, __ATOMIC_RELAXED, __MEMORY_SCOPE_SYSTEM);
+  // CIR-BEFORE-TL: cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // LLVM: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
   // OGCG: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
@@ -103,11 +105,13 @@ void scoped_atomic_exchange_n(int *ptr, int value) {
   // OGCG-LABEL: @scoped_atomic_exchange_n
 
   __scoped_atomic_exchange_n(ptr, value, __ATOMIC_RELAXED, __MEMORY_SCOPE_SINGLE);
-  // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(single_thread) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
+  // CIR-BEFORE-TL: cir.atomic.xchg relaxed syncscope(single_thread) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
+  // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // LLVM: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
   // OGCG: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
 
   __scoped_atomic_exchange_n(ptr, value, __ATOMIC_RELAXED, __MEMORY_SCOPE_SYSTEM);
+  // CIR-BEFORE-TL: cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // CIR: %{{.+}} = cir.atomic.xchg relaxed syncscope(system) %{{.+}}, %{{.+}} : (!cir.ptr<!s32i>, !s32i) -> !s32i
   // LLVM: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4
   // OGCG: %{{.+}} = atomicrmw xchg ptr %{{.+}}, i32 %{{.+}} monotonic, align 4

``````````

</details>


https://github.com/llvm/llvm-project/pull/180744