[flang] [llvm] [mlir] [flang][llvm][OpenMP][OpenACC] Add implicit casts to omp.atomic and acc.atomic (PR #131603)

[Tom Eccles via llvm-commits]

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@@ -0,0 +1,57 @@
+! REQUIRES : openmp_runtime
+
+! RUN: %flang_fc1 -emit-hlfir %openmp_flags %s -o - | FileCheck %s
+
+! CHECK: func.func @_QPatomic_implicit_cast_read() {
+subroutine atomic_implicit_cast_read
+! CHECK: %[[ALLOCA3:.*]] = fir.alloca complex<f64>
+! CHECK: %[[ALLOCA2:.*]] = fir.alloca i32
+! CHECK: %[[ALLOCA1:.*]] = fir.alloca f64
+! CHECK: %[[ALLOCA0:.*]] = fir.alloca i32
+
+
+! CHECK: %[[M:.*]] = fir.alloca complex<f64> {bindc_name = "m", uniq_name = "_QFatomic_implicit_cast_readEm"}
+! CHECK: %[[M_DECL:.*]]:2 = hlfir.declare %[[M]] {uniq_name = "_QFatomic_implicit_cast_readEm"} : (!fir.ref<complex<f64>>) -> (!fir.ref<complex<f64>>, !fir.ref<complex<f64>>)
+! CHECK: %[[W:.*]] = fir.alloca complex<f32> {bindc_name = "w", uniq_name = "_QFatomic_implicit_cast_readEw"}
+! CHECK: %[[W_DECL:.*]]:2 = hlfir.declare %[[W]] {uniq_name = "_QFatomic_implicit_cast_readEw"} : (!fir.ref<complex<f32>>) -> (!fir.ref<complex<f32>>, !fir.ref<complex<f32>>)
+! CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFatomic_implicit_cast_readEx"}
+! CHECK: %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFatomic_implicit_cast_readEx"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[Y:.*]] = fir.alloca f32 {bindc_name = "y", uniq_name = "_QFatomic_implicit_cast_readEy"}
+! CHECK: %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFatomic_implicit_cast_readEy"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
+! CHECK: %[[Z:.*]] = fir.alloca f64 {bindc_name = "z", uniq_name = "_QFatomic_implicit_cast_readEz"}
+! CHECK: %[[Z_DECL:.*]]:2 = hlfir.declare %[[Z]] {uniq_name = "_QFatomic_implicit_cast_readEz"} : (!fir.ref<f64>) -> (!fir.ref<f64>, !fir.ref<f64>)
+    integer :: x
+    real :: y
+    double precision :: z
+    complex :: w
+    complex(8) :: m
+
+! CHECK: %[[LOAD:.*]] = fir.load %[[Y_DECL]]#0 : !fir.ref<f32>
+! CHECK: %[[CVT:.*]] = fir.convert %[[LOAD]] : (f32) -> i32
+! CHECK: fir.store %[[CVT]] to %[[ALLOCA0]] : !fir.ref<i32>
+! CHECK: omp.atomic.read %[[X_DECL]]#0 = %[[ALLOCA0]] : !fir.ref<i32>, !fir.ref<i32>, i32
+    !$omp atomic read
+        x = y
----------------
tblah wrote:

I think this is still the wrong way around. In this code `y` is read from non-atomically (`fir.load`), then stored in a temporary of the right type and it is that temporary which is read from atomically.

The correct code sequence for an atomic *read* would be something like
```
%x_tmp = fir.alloca f32
omp.atomic read %x_tmp = %y : !fir.ref<f32>, !fir.ref<f32>, f32
%f32_val = fir.load %x_tmp
%i32_val = fir.convert %f32_val : (f32) -> i32
fir.store %i32_val to %x
```

Of course for an atomic write things would be the other way around.

https://github.com/llvm/llvm-project/pull/131603