Re: [RFC] internal documentation for OMP_FOR

[Tobias Burnus <tobias@codesourcery.com>]

Hi Sandra,

https://gcc.gnu.org/pipermail/gcc-patches/2023-February/612298.html

On 19.02.23 06:21, Sandra Loosemore wrote:
> Here is a patch I put together for the internals manual; can other
> people familiar with this functionality review it for technical
> correctness?

Glancing at it,  it seems to be okay. (I have not cross checked by looking at the code.)


However, you may want to add something related to non-rectangular loops. For those, the
'N1' in OMP_FOR_INIT's @code{VAR = N1} and the
'N2' in OMP_FOR_COND's @code{VAR @{<,>,<=,>=@} N2}
have a special form; namely, the N1 and/or N2 are not normal expressions
but are TREE_VEC with three elements:
The outer loop variable (TREE_CODE_CLASS == tcc_declaration),
a multiplication factor,
and an offset.

Example: For the loop initialization 'i = j - 5', the result to be put into the
OMP_FOR_INIT vector is: 'MODIFY_EXPR (i, TREE_VEC<j, 1, -5>)'

You could then also mention that OMP_FOR_NON_RECTANGULAR is/must be set
on the OMP_FOR statement in that case. (This flag is currently not mentioned in the .texi.)


Additionally, the doc/generic.texi could also mention that not only OMP_FOR
takes those operands but also OMP_SIMD, OMP_DISTRIBUTE, OMP_TASKLOOP, OMP_LOOP,
and OACC_LOOP (cf. tree.def or the actual code using it).

Tobias

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