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

[Tom Eccles via llvm-commits]

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@@ -386,6 +442,7 @@ void genOmpAccAtomicRead(Fortran::lower::AbstractConverter &converter,
       fir::getBase(converter.genExprAddr(fromExpr, stmtCtx));
   mlir::Value toAddress = fir::getBase(converter.genExprAddr(
       *Fortran::semantics::GetExpr(assignmentStmtVariable), stmtCtx));
+  emitImplicitCast(converter, loc, fromAddress, toAddress, elementType);
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tblah wrote:

I'm worried that this helper creates a non-atomic read. If I am reading the changes correctly, you're loading and converting into the alloca non-atomically, and then doing an atomic load from the alloca.

The load from the original memory address needs to be atomic. I think you need to load atomically in the original datatype, and then convert the result of that.

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