[PATCH] D74144: [OPENMP50]Add basic support for array-shaping operation.

[Alexey Bataev via Phabricator via cfe-commits]

ABataev added a comment.



In D74144#2307454 <https://reviews.llvm.org/D74144#2307454>, @cchen wrote:

> @ABataev, the below test is extracted from Sollve test suite and Clang now emit:
>
>   test.c:17:35: error: subscripted value is not an array or pointer
>       #pragma omp target update to( (([N][N])foo)[1:M] )
>                                     ^~~~~~~~~~~~~
>   test.c:17:5: error: expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'
>       #pragma omp target update to( (([N][N])foo)[1:M] )
>
> This error message came from the `ActOnOMPArraySectionExpr` which is called inside `ParsePostfixExpressionSuffix`. The issue is that the base expression in `ActOnOMPArraySectionExpr` looks like:
>
>   ParenExpr 0x122859be0 '<OpenMP array shaping type>' lvalue
>   `-OMPArrayShapingExpr 0x122859b98 '<OpenMP array shaping type>' lvalue
>     |-IntegerLiteral 0x122859b38 'int' 5
>     |-IntegerLiteral 0x122859b58 'int' 5
>     `-DeclRefExpr 0x122859b78 'int *' lvalue Var 0x1228599d0 'foo' 'int *'
>
> which is not a base that we would expect in an array section expr. I've tried relaxing the base type check in `ActOnOMPArraySectionExpr` but not sure it's the way to go. (or should I just extract the DeclReExpr from ArrayShapingExpr before calling `ActOnOMPArraySectionExpr`?)
>
>   #define N 5
>   #define M 3
>   
>   int main(void) {
>       int tmp[N][N];
>       for(int i=0; i<N; i++)
>           for(int j=0; j<N; j++)
>               tmp[i][j] = N*i + j;
>   
>       int *foo = &tmp[0][0];
>   
>       // This compiles just fine
>       //#pragma omp target update to( ([N][N])foo )
>   
>       // This is rejected by the compiler
>       #pragma omp target update to( (([N][N])foo)[1:M] )
>   }

I don't think it is allowed by the standard.

According to the standard, The shape-operator can appear only in clauses where it is explicitly allowed.
In this case, array shaping is used as a base expression of array section (or subscript) expression, which does not meet the standard. Tje array sjaping operation is not used in clause, instead it is used as a base subexpression of another expression.


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https://reviews.llvm.org/D74144