[Mlir-commits] [flang] [mlir] [Flang] [OpenMP] atomic compare (PR #184761)

[llvmlistbot at llvm.org]

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@@ -2452,6 +2452,95 @@ llvm.func @omp_atomic_capture_misc(
 
 // -----
 
+// CHECK-LABEL: @omp_atomic_compare
+// CHECK-SAME: (ptr %[[X:.*]], i32 %[[E:.*]], i32 %[[D:.*]], ptr %[[XF:.*]], float %[[EF:.*]], float %[[DF:.*]], ptr %[[XC:.*]], { float, float } %[[EC:.*]], { float, float } %[[DC:.*]])
+llvm.func @omp_atomic_compare(
+  %x : !llvm.ptr, %e : i32, %d : i32,
+  %xf : !llvm.ptr, %ef : f32, %df : f32,
+  %xc : !llvm.ptr, %ec : !llvm.struct<(f32, f32)>, %dc : !llvm.struct<(f32, f32)>) {
+
+  // Integer equality  →  cmpxchg
+  // CHECK: cmpxchg ptr %[[X]], i32 %[[E]], i32 %[[D]] monotonic monotonic
+  omp.atomic.compare %x : !llvm.ptr {
+  ^bb0(%xval : i32):
+    %cmp0 = llvm.icmp "eq" %xval, %e : i32
+    %sel0 = llvm.select %cmp0, %d, %xval : i1, i32
+    omp.yield(%sel0 : i32)
+  }
+
+  // Float equality  →  bitcast + cmpxchg
+  // CHECK: %[[EBC:.*]] = bitcast float %[[EF]] to i32
+  // CHECK: %[[DBC:.*]] = bitcast float %[[DF]] to i32
+  // CHECK: cmpxchg ptr %[[XF]], i32 %[[EBC]], i32 %[[DBC]] monotonic monotonic
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SunilKuravinakop wrote:

CAS loops i.e. `load,` `fcmp oeq`, `compxchg` (on successfull fcmp) has to be done for this. This is not an atomic instruction. Do you know of any alternative where it can done as an atomic instruction?

https://github.com/llvm/llvm-project/pull/184761