Summary:
The AMDGPU backend uses the linker-provided INIT_ARRAY and FINI_ARRAY
sections to call all the global constructors in a single kernel.
Previously this mistakenly used the same iteration logic for both
arrays. The destructors stored in FINI_ARRAY are stored in the same
order as
the ones in the INIT_ARRAY section so we need to traverse it in reverse
order.
Relanding after the revert in fe7b5e2cfcf6848287010291081f85fa1f6bb2ef
using the IR builder interface instead of ConstantExpr.
Summary:
The AMDGPU backend uses the linker-provided INIT_ARRAY and FINI_ARRAY
sections to call all the global constructors in a single kernel.
Previously this mistakenly used the same iteration logic for both
arrays. The destructors stored in FINI_ARRAY are stored in the same
order as
the ones in the INIT_ARRAY section so we need to traverse it in reverse
order.
There are many tests that specify a target triple/CPU flags but no
DataLayout which can lead to IR being generated that has unusual
behaviour. This commit attempts to use the default DataLayout based
on the relevant flags if there is no explicit override on the command
line or in the IR file.
One thing that is not currently possible to differentiate from a missing
datalayout `target datalayout = ""` in the IR file since the current
APIs don't allow detecting this case. If it is considered useful to
support this case (instead of passing "-data-layout=" on the command
line), I can change IR parsers to track whether they have seen such a
directive and change the callback type.
Differential Revision: https://reviews.llvm.org/D141060
We only expect these ctor / dtor functions to be called with a single
thread. Add the appropriate attributes to indicate this to the backend.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D151153
Currently AMDGPU offers extra ctor / dtor lowering by emitting a kernel
that can be called. It's possible to handle ctors and dtors using the
standard method as shown in D149340's commit message. In which case we
on't need these extra kernels as they won't be called. This patch simply
adds a way to conditionally turn off this handling if we do not want to
get extra kernels in the output.
Unrelated, but we could convert this handling to an ODR function that simply
calls the code in D149340 constructed via LLVM-IR. That would handle priority
correctly and would then be correct if not run in LTO mode.
Reviewed By: yaxunl
Differential Revision: https://reviews.llvm.org/D150565
Currently, AMDGPU has special handling for constructors and destructors.
We manuall emit a kernel that calls the functoins listed in the global
constructor / destructor list. This currently has two main problems. The
first is that we do not repsect the priortiy and simply call them in any
order. The second is that we redefine the symbol unconditionally which
coulid have a different definition, meaning we cannot merge any code
with a constructor post-codegen. This patch changes the handling to
instead use the standard support for travering the `.init_array` and
`.fini_array` sections the compiler creates. This allows us to emit a
single kernel with `odr` semantics, so even if we emit this multiple
times they will be merged into a single kernel.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D150675
For the GPU, we emit external kernels that call the initializers and
constructors, however if we had a persistent kernel like in the `_start`
kernel for the `libc` project, we could initialize the standard way of
calling constructors. This patch adds new global variables containing
pointers to the constructors to be called. If these are placed in the
`.init_array` and `.fini_array` sections, then the backend will handle
them specially. The linker will then provide the `__init_array_` and
`__fini_array_` sections to traverse them. An implementation would look
like this.
```
extern uintptr_t __init_array_start[];
extern uintptr_t __init_array_end[];
extern uintptr_t __fini_array_start[];
extern uintptr_t __fini_array_end[];
using InitCallback = void(int, char **, char **);
using FiniCallback = void(void);
extern "C" [[gnu::visibility("protected"), clang::amdgpu_kernel]] void
_start(int argc, char **argv, char **envp) {
uint64_t init_array_size = __init_array_end - __init_array_start;
for (uint64_t i = 0; i < init_array_size; ++i)
reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
uint64_t fini_array_size = __fini_array_end - __fini_array_start;
for (uint64_t i = 0; i < fini_array_size; ++i)
reinterpret_cast<FiniCallback *>(__fini_array_start[i])();
}
```
Reviewed By: yaxunl
Differential Revision: https://reviews.llvm.org/D149340
We should be able to run the pass multiple times without breaking
anything. If we still need to track these for some reason, we could
replace with new entries for the kernels.
HSA runtime fails to find the symbols for Init and Fini kernels as
they mark with internal linkage, changing the linkage to external
to fix those errors.
Differential Revision: https://reviews.llvm.org/D110054
This patch introduces a new code object metadata field, ".kind"
which is used to add support for init and fini kernels.
HSAStreamer will use function attributes, "device-init" and
"device-fini" to distinguish between init and fini kernels from
the regular kernels and will emit metadata with ".kind" set to
"init" and "fini" respectively.
To reduce the number of init and fini kernels, the ctors and
dtors present in the llvm's global.ctors and global.dtors lists
are called from a single init and fini kernel respectively.
Reviewed by: yaxunl
Differential Revision: https://reviews.llvm.org/D105682
This patch introduces a new code object metadata field, ".kind"
which is used to add support for init and fini kernels.
HSAStreamer will use function attributes, "device-init" and
"device-fini" to distinguish between init and fini kernels from
the regular kernels and will emit metadata with ".kind" set to
"init" and "fini" respectively.
To reduce the number of init and fini kernels, the ctors and
dtors present in the llvm's global.ctors and global.dtors lists
are called from a single init and fini kernel respectively.
Reviewed by: yaxunl
Differential Revision: https://reviews.llvm.org/D105682
