[flang-commits] [flang] [mlir] [flang][OpenMP] Support for "atomic compare capture" (PR #202315)

[Tom Eccles via flang-commits]

================
@@ -617,6 +646,17 @@ void Fortran::lower::omp::lowerAtomic(
       expectedVal = builder.createConvert(loc, elemTypeOfX, expectedVal);
     }
 
+    // If this is a compare+capture, generate the read op first.
+    if (construct.IsCapture()) {
+      assert(get(analysis.op0.assign) && (analysis.op0.what & analysis.Read) &&
+             "Expected a read operation for compare capture");
----------------
tblah wrote:

This assert is reachable e.g.
```
subroutine s_prefix(x, e, d, v)
  integer :: x, e, d, v
  !$omp atomic compare capture
  if (x .eq. e) x = d
  v = x
  !$omp end atomic
end subroutine
```

https://github.com/llvm/llvm-project/pull/202315