[llvm-branch-commits] [flang] [llvm] [flang][OpenMP] Don't treat different runtime conditions as subsets (PR #233493)

[via llvm-branch-commits]

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@@ -2579,6 +2585,24 @@ std::optional<MetadirectiveCandidateSet> BuildMetadirectiveCandidateSet(
     return spec.DirId() == llvm::omp::Directive::OMPD_nothing ? nullptr : &spec;
   };
 
+  // Identify each distinct runtime condition, so that different conditions
+  // are not strict subsets of each other.
+  llvm::SmallVector<SomeExpr, 4> runtimeConditions;
+  auto getConditionKey = [&](const DynamicUserCondition &condition) {
+    const SomeExpr *expr{GetExpr(context, *condition.expr)};
+    if (!expr ||
+        evaluate::IsActuallyConstant(
----------------
MattPD wrote:

Could `EvaluateUserCondition` and `getConditionKey` share the truth-value classification of folded logical constants? `EvaluateUserCondition` returns `nullopt` for `.false._8`, while `getConditionKey` recognizes it as constant. In this reproducer, [the base](https://github.com/llvm/llvm-project/commit/6278453680db4f0058ca12663f87b84c1b914ea4) emits unconditional TASKYIELD, but the reviewed head emits TASKWAIT when `b` is true.

You can reproduce this by saving the following as `repro.f90` and running `flang -fopenmp -fopenmp-version=52 -S -emit-llvm repro.f90 -o -`:

```fortran
subroutine false_constant(b)
  logical, intent(in) :: b
  !$omp metadirective &
  !$omp& when(device={kind(host)}, implementation={vendor(score(3): llvm)}: taskyield) &
  !$omp& when(user={condition(b)}, implementation={vendor(score(4): llvm)}: taskwait) &
  !$omp& when(user={condition(.false._8)}, device={kind(host)}, &
  !$omp& implementation={vendor(score(3): llvm)}: barrier)
end subroutine
```

Replacing `.false._8` with the default-kind literal `.false.` produces the same selection change under `-fdefault-integer-8`.

https://github.com/llvm/llvm-project/pull/233493