forked from OSchip/llvm-project
73026a4fbf
Array-value-copy fails to generate a temporary array for case like this:
subroutine bug(b)
real, allocatable :: b(:)
b = b(2:1:-1)
end subroutine
Since LHS may need to be reallocated, lowering produces the following FIR:
%rhs_load = fir.array_load %b %slice
%lhs_mem = fir.if %b_is_allocated_with_right_shape {
fir.result %b
} else {
%new_storage = fir.allocmem %rhs_shape
fir.result %new_storage
}
%lhs = fir.array_load %lhs_mem
%loop = fir.do_loop {
....
}
fir.array_merge_store %lhs, %loop to %lhs_mem
// deallocate old storage if reallocation occured,
// and update b descriptor if needed.
Since %b in array_load and %lhs_mem in array_merge_store are not the same SSA
values, array-value-copy does not detect the conflict and does not produce
a temporary array. This causes incorrect result in runtime.
The suggested change in lowering is to generate this:
%rhs_load = fir.array_load %b %slice
%lhs_mem = fir.if %b_is_allocated_with_right_shape {
%lhs = fir.array_load %b
%loop = fir.do_loop {
....
}
fir.array_merge_store %lhs, %loop to %b
fir.result %b
} else {
%new_storage = fir.allocmem %rhs_shape
%lhs = fir.array_load %new_storage
%loop = fir.do_loop {
....
}
fir.array_merge_store %lhs, %loop to %new_storage
fir.result %new_storage
}
// deallocate old storage if reallocation occured,
// and update b descriptor if needed.
Note that there are actually 3 branches in FIR, so the assignment loops
are currently produced in three copies, which is a code-size issue.
It is possible to generate just two branches with two copies of the loops,
but it is not addressed in this change-set.
Differential Revision: https://reviews.llvm.org/D129314
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| .. | ||
| Common | ||
| Decimal | ||
| Evaluate | ||
| Frontend | ||
| FrontendTool | ||
| Lower | ||
| Optimizer | ||
| Parser | ||
| Semantics | ||
| CMakeLists.txt | ||