[all-commits] [llvm/llvm-project] a2d74b: [flang][OpenMP] Implement the error directive (#20...

[Caroline Newcombe via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a2d74bfe386695ee1a17ba3b60367fb79c3bfdfe
      https://github.com/llvm/llvm-project/commit/a2d74bfe386695ee1a17ba3b60367fb79c3bfdfe
  Author: Caroline Newcombe <caroline.newcombe at hpe.com>
  Date:   2026-07-24 (Fri, 24 Jul 2026)

  Changed paths:
    M flang/include/flang/Semantics/openmp-utils.h
    M flang/lib/Lower/OpenMP/OpenMP.cpp
    M flang/lib/Semantics/check-omp-structure.cpp
    M flang/lib/Semantics/check-omp-structure.h
    M flang/lib/Semantics/openmp-utils.cpp
    R flang/test/Lower/OpenMP/Todo/error.f90
    A flang/test/Lower/OpenMP/error.f90
    M flang/test/Parser/OpenMP/error-unparse.f90
    M flang/test/Semantics/OpenMP/error.f90
    M llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h
    M llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
    M mlir/include/mlir/Dialect/OpenMP/OpenMPEnums.td
    M mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td
    M mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
    M mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
    M mlir/test/Dialect/OpenMP/invalid.mlir
    M mlir/test/Dialect/OpenMP/ops.mlir
    M mlir/test/Target/LLVMIR/openmp-llvm.mlir

  Log Message:
  -----------
  [flang][OpenMP] Implement the error directive (#206175)

## [flang][OpenMP] Implement the `error` directive

### Summary

Implements the OpenMP `error` directive (OpenMP 5.1, 2.5.4) in Flang.
The directive prints a message and, with `severity(fatal)`, stops.
Handling depends on the `at` clause:

- **`at(compilation)`** (the default): handled in semantics. Emits a
compile-time warning or error and produces no IR.
- **`at(execution)`**: lowered to a new `omp.error` op, which becomes a
call to `__kmpc_error`.

Before this patch the directive was unimplemented and hit a `not yet
implemented: OmpErrorDirective` error during lowering.

Fixes #204240.

### Details

Changes go through the compiler pipeline.

**Flang semantics**
- `Enter(OmpErrorDirective)` emits the compile-time diagnostic for the
`at(compilation)` form, using the directive's severity and the `MESSAGE`
text when present.
- `Enter(OmpClause::Message)` checks that the `MESSAGE` expression is a
scalar, default-kind `CHARACTER`, which is required to pass it to the
runtime as a `const char*`.

**Flang lowering**
- `genErrorDirective` lowers the `at(execution)` form only.
- A constant message is stored in the `message` attribute. A
non-constant message is copied to a null-terminated buffer
(`genNullTerminatedString`) and passed as the `message_expr` operand,
because `__kmpc_error` expects a NUL-terminated string.

**New `omp.error` op (MLIR OpenMP dialect)**
- Adds a `ClauseSeverity` enum (`warning = 1`, `fatal = 2`, matching the
`__kmpc_error` argument) and `ClauseSeverityAttr`.
- `omp.error` takes a required `severity` attribute and an optional
message, given either as:
  - `message` — a constant string attribute, or
  - `message_expr` — a pointer to a null-terminated string.
- A verifier rejects providing both `message` and `message_expr`.

**MLIR → LLVM IR translation**
- Translates `omp.error` to `__kmpc_error(ident_t *, i32 severity, ptr
message)`.

**OMPIRBuilder**
- Adds `OpenMPIRBuilder::createError(...)`, which builds the call, maps
`fatal`→`2` and `warning`→`1`, and passes a null pointer when there is
no message.

### Tests

- **Parser** (`error-unparse.f90`): unparse and parse-tree output.
`at(compilation) severity(fatal)` cases that would stop compilation were
moved to `at(execution)`.
- **Semantics** (`Semantics/OpenMP/error.f90`): compilation
warning/error/default-severity cases, plus the new `MESSAGE` type, rank,
and kind errors.
- **Lowering** (`Lower/OpenMP/error.f90`): constant message, no message,
empty message, runtime `message_expr`, and `at(compilation)` cases that
must not produce `omp.error`. The old `Lower/OpenMP/Todo/error.f90` test
is removed.
- **MLIR** (`ops.mlir`, `invalid.mlir`): round-trip of each `omp.error`
form and the both-messages verifier error.
- **LLVM IR** (`openmp-llvm.mlir`): `__kmpc_error` calls for warning and
fatal, constant and runtime messages, and the null-message cases.

Assisted-by: Github Copilot



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