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[Flang][Doc] NFC: Minor fix for headings #147077

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Jul 7, 2025
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[Flang][Doc] NFC: Minor fix for headings #147077

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20 changes: 14 additions & 6 deletions flang/docs/OpenMP-declare-target.md
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Expand Up @@ -7,7 +7,15 @@

-->

# Introduction to Declare Target
# OpenMP Declare Target

```{contents}
---
local:
---
```

## Introduction to Declare Target

In OpenMP `declare target` is a directive that can be applied to a function or
variable (primarily global) to notate to the compiler that it should be
Expand Down Expand Up @@ -55,7 +63,7 @@ in this case, leave off the `declare target` from the function and it
would be implicitly marked `declare target any` (for both host and device),
as it's been utilised within a target region.

# Declare Target as represented in the OpenMP Dialect
## Declare Target as represented in the OpenMP Dialect

In the OpenMP Dialect `declare target` is not represented by a specific
`operation`. Instead, it's an OpenMP dialect specific `attribute` that can be
Expand Down Expand Up @@ -89,7 +97,7 @@ llvm::dyn_cast<mlir::omp::DeclareTargetInterface>(Op.getOperation());
declareTargetGlobal.isDeclareTarget();
```

# Declare Target Fortran OpenMP Lowering
## Declare Target Fortran OpenMP Lowering

The initial lowering of `declare target` to MLIR for both use-cases is done
inside of the usual OpenMP lowering in flang/lib/Lower/OpenMP.cpp. However,
Expand Down Expand Up @@ -145,7 +153,7 @@ to the way `threadprivate` handles these cases, we raise and initialize the
variable as an internal `GlobalOp` and apply the attribute. This occurs in the
flang/lib/Lower/OpenMP.cpp function `genDeclareTargetIntGlobal`.

# Declare Target Transformation Passes for Flang
## Declare Target Transformation Passes for Flang

There are currently two passes within Flang that are related to the processing
of `declare target`:
Expand Down Expand Up @@ -173,7 +181,7 @@ While this infrastructure could be generally applicable to more than just Flang,
it is only utilised in the Flang frontend, so it resides there rather than in
the OpenMP dialect codebase.

# Declare Target OpenMP Dialect To LLVM-IR Lowering
## Declare Target OpenMP Dialect To LLVM-IR Lowering

The OpenMP dialect lowering of `declare target` is done through the
`amendOperation` flow, as it's not an `operation` but rather an
Expand Down Expand Up @@ -228,7 +236,7 @@ place. It may be possible to store this information in the OMPIRBuilder and
then perform this cleanup process on finalization, but this is open for
discussion and implementation still.

# Current Support
## Current Support

For the moment, `declare target` should work for:
* Marking functions/subroutines and function/subroutine interfaces for
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11 changes: 9 additions & 2 deletions flang/docs/OpenMP-descriptor-management.md
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-->

# OpenMP dialect: Fortran descriptor type mapping for offload
# Fortran descriptor type mapping for OpenMP offload
```{contents}
---
local:
---
```


## Details
The initial method for mapping Fortran types tied to descriptors for OpenMP offloading is to treat these types
as a special case of OpenMP record type (C/C++ structure/class, Fortran derived type etc.) mapping as far as the
runtime is concerned. Where the box (descriptor information) is the holding container and the underlying
Expand Down Expand Up @@ -103,7 +110,7 @@ it is a little rigid in how the descriptor mappings are handled as there is no s
to specialise the mappings for possible edge cases without polluting the dialect or lowering with further
knowledge of Fortran and the FIR dialect.

# OpenMP dialect differences from OpenACC dialect
## Differences from OpenACC

The descriptor mapping for OpenMP currently works differently to the planned direction for OpenACC, however,
it is possible and would likely be ideal to align the method with OpenACC in the future.
Expand Down
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