In order to get the pointer to a structure member, `getelementptr`
typically requires two indices: one to indicate the structure itself,
and another to specify the member's position. We are missing the former
in `GPULaunchKernelConversion`, so generated code may cause stack
corruption. This PR corrects the indices of a structure used as a kernel
launch temp.
For the call to _FortranACUFLaunchKernel, we store the pointer to a
member of a temporary structure in a parameter array. However, when we
obtain an element pointer from the parameter array, its address is
calculated based on the type of the structure. This PR properly treats
the parameter array as an array of pointers.
Example:
```mlir
%30 = llvm.load %29 : !llvm.ptr -> i32
%31 = llvm.mlir.constant(1 : i32) : i32
%32 = llvm.alloca %31 x !llvm.struct<(i64, i64, i32, ptr)> : (i32) -> !llvm.ptr
%33 = llvm.mlir.constant(4 : i32) : i32
%34 = llvm.alloca %33 x !llvm.ptr : (i32) -> !llvm.ptr
%35 = llvm.mlir.constant(0 : i32) : i32
%36 = llvm.getelementptr %32[%35] : (!llvm.ptr, i32) -> !llvm.ptr, !llvm.struct<(i64, i64, i32, ptr)>
llvm.store %8, %36 : i64, !llvm.ptr
%37 = llvm.getelementptr %34[%35] : (!llvm.ptr, i32) -> !llvm.ptr, !llvm.struct<(i64, i64, i32, ptr)>
llvm.store %36, %37 : !llvm.ptr, !llvm.ptr
...
llvm.call @_FortranACUFLaunchKernel(%47, %8, %8, %8, %2, %8, %8, %7, %34, %48) : (!llvm.ptr, i64, i64, i64, i64, i64, i64, i32, !llvm.ptr, !llvm.ptr) -> ()
```
In this example, `%37 = llvm.getelementptr %34[%35] : (!llvm.ptr, i32)
-> !llvm.ptr, !llvm.struct<(i64, i64, i32, ptr)>` will be `%37 =
llvm.getelementptr %34[%35] : (!llvm.ptr, i32) -> !llvm.ptr, !llvm.ptr`.
Use `pm.nest` to schedule the pass on nested `func.func` and `gpu.func`
in the `gpu.module`.
AbstractResult pass is not meant to run on the whole gpu.module at once.
1. In `CufOpConversion` `isDeviceGlobal` was renamed
`isRegisteredGlobal` and moved to the common file. `isRegisteredGlobal`
excludes constant `fir.global` operation from registration. This is to
avoid calls to `_FortranACUFGetDeviceAddress` on globals which do not
have any symbols in the runtime. This was done for
`_FortranACUFRegisterVariable` in #118582, but also needs to be done
here after #118591
2. `CufDeviceGlobal` no longer adds the `#cuf.cuda<constant>` attribute
to the constant global. As discussed in #118582 a module variable with
the #cuf.cuda<constant> attribute is not a compile time constant. Yet,
the compile time constant also needs to be copied into the GPU module.
The candidates for copy to the GPU modules are
- the globals needing regsitrations regardless of their uses in device
code (they can be referred to in host code as well)
- the compile time constant when used in device code
3. The registration of "constant" module device variables (
#cuf.cuda<constant>) can be restored in `CufAddConstructor`
Add pattern that update fir.declare memref when it comes from a device
global and is not a descriptor. In that case, we recover the device
address that needs to be used in ops like `fir.array_coor` and so on.
Global constants have no symbols in library files. They are replaced
with literal constants during lowering before kernels are moved into a
GPU module. Do not register them because they will result in unresolved
symbols.
in CUDA Fortran, device function are converted to `gpu.func` inside the
`gpu.module` operation. Update the AbstractResult pass to be able to run
on `func.func` and `gpu.func` operations inside the `gpu.module`.
Materialize the box when the src comes from a embox or rebox operation.
This was done in the case of transfer to a descriptor but not when
transferring from a descriptor.
fir.call side effects are hard to describe in a useful way using
`MemoryEffectOpInterface` because it is impossible to list which memory
location a user procedure read/write without doing a data flow analysis
of its body (even PURE procedures may read from any module variable,
Fortran SIMPLE procedure from F2023 will allow that, but they are far
from common at that point).
Fortran language specifications allow the compiler to deduce
that a procedure call cannot access a variable in many cases
This patch leverages this to extend `fir::AliasAnalysis::getModRef` to
deal with fir.call.
This will allow implementing "array = array_function()" optimization in
a future patch.
- Update the runtime entry points to accept a stream information
- Update the conversion of `cuf.allocate` to pass correctly the stream
information when present.
Note that the stream is not currently used in the runtime. This will be
done in a separate patch as a design/solution needs to be down together
with the allocators.
When the src of the data transfer is a constant, it needs to be
materialized in memory to be able to perform a data transfer.
```
subroutine sub1()
real, device :: a(10)
integer :: I
do i = 5, 10
a(i) = -4.0
end do
end
```
Update the implicit global detection by looking for them in the CUF
kernel and also update to a walk so nested `fir.address_of` in nested
statement are also accounted for.
This PR adds the handling of `ClassType`. It is treated as pointer to
the underlying type. Note that `ClassType` when passed to the function
have double indirection so it is represented as pointer to type
(compared to other types which may have a single indirection).
If `ClassType` wraps a pointer or allocatable then we take care to
generate it as PTR -> type (and not PTR -> PTR -> type).
This is how it looks like in the debugger.
```
subroutine test_proc (this)
class(test_type), intent (inout) :: this
allocate (this%b (3, 2))
call fill_array_2d (this%b)
print *, this%a
end
```
```
(gdb) p this
$6 = (PTR TO -> ( Type test_type )) 0x2052a0
(gdb) p this%a
$7 = 0
(gdb) p this%b
$8 = ((1, 2, 3) (4, 5, 6))
```
The runtime Assign function is not meant to initialize an array from a
scalar. For that we need to use DoAssignFromSource. Update the data
transfer from scalar to descriptor to use a new entry point that use
this function underneath.
When an array is declared with a non default lower bound, the declare op
`getShape` will return a `ShapeShiftOp`. This result is used in data
transfer operation to compute the number of bytes to transfer. Update
the op to support `ShapeShiftOp`.
Number of bytes to allocate was not computed when using `cuf.alloc` with
a derived type. Update the conversion to compute the number of bytes and
emit an error when type is not supported.
Data transfer from a variable with a descriptor to a pointer. We create
a descriptor for the pointer so we can use the flang runtime to perform
the transfer. The Assign function handles all corner cases. We add a new
entry points `CUFDataTransferDescDescNoRealloc` to avoid reallocation
since the variable on the LHS is not an allocatable.
The assumed-rank array are represented by DIGenericSubrange in debug
metadata. We have to provide 2 things.
1. Expression to get rank value at the runtime from descriptor.
2. Assuming the dimension number for which we want the array information
has been put on the DWARF expression stack, expressions which will
extract the lowerBound, count and stride information from the descriptor
for the said dimension.
With this patch in place, this is how I see an assumed_rank variable
being evaluated by GDB.
```
function mean(x) result(y)
integer, intent(in) :: x(..)
...
end
program main
use mod
implicit none
integer :: x1,xvec(3),xmat(3,3),xtens(3,3,3)
x1 = 5
xvec = 6
xmat = 7
xtens = 8
print *,mean(xvec), mean(xmat), mean(xtens), mean(x1)
end program main
(gdb) p x
$1 = (6, 6, 6)
(gdb) p x
$2 = ((7, 7, 7) (7, 7, 7) (7, 7, 7))
(gdb) p x
$3 = (((8, 8, 8) (8, 8, 8) (8, 8, 8)) ((8, 8, 8) (8, 8, 8) (8, 8, 8)) ((8, 8, 8) (8, 8, 8) (8, 8, 8)))
(gdb) p x
$4 = 5
```
When source is a pointer to an array or a scalar, embox it and use the
`CUFDataTransferDescDesc` or `CUFDataTransferGlobalDescDesc` entry
points. The runtime is already able to deal with all the corner cases
like non contiguous arrays and so on so we exploit this.
Memset might still be used for simple case where we want to initialize
to 0 for example. This will come in a follow up patch.
When the destination of the data transfer is a global we might need to
sync the descriptor after the data transfer is done. This is the case
when the data transfer is from host/device to device as reallocation
might have happened and the descriptor on the device needs to take the
new values written on the host.
A new entry point is added `CUFDataTransferGlobalDescDesc` with the sync
when needed.
Passing a descriptor as a `const Descriptor &` or a `const Descriptor *`
generates a FIR signature where the box is passed by value.
This is an issue, as it requires a load of the box to be passed. But
since, ultimately, all boxes are passed by reference a temporary is
generated in LLVM and the reference to the temporary is passed.
The boxes addresses are registered with the CUDA runtime but the
temporaries are not, thus preventing the runtime to properly map a host
side address to its device side counterpart.
To address this issue, this PR changes the signatures to the transfer
functions to pass a descriptor as a `Descriptor *`, which will in turn
generate a FIR signature with that takes a box reference as an argument.
Handling is similar to RecordType with following differences:
1. No check for cyclic references
2. No extra processing for lower bounds of array members.
3. No line information as TupleType is a lowering artefact and does not
really represent an entity in the code.
