Flat scratch instructions (aka private) are the 3rd and final segment of
flat instructions in gfx9 (Vega) and beyond. These are used for things
like spills/fills and thread local storage. This commit enables two
forms of flat scratch instructions: (1) flat_load/flat_store
instructions where the memory address resolves to private memory and (2)
the new scratch_load/scratch_store instructions in Vega. The first are
similar to older generation ISAs where the aperture is unknown until
address translation. The second are instructions guaranteed to go to
private memory.
Since these are very similar to flat global instructions there are
minimal changes needed:
- Ensure a flat instruction is either regular flat, global, XOR scratch
- Rename the global op_encoding methods to GlobalScratch to indicate
they are for both and are intentionally used.
- Flat instructions in segment 1 output scratch_ in the disassembly
- Flat instruction executed as private use similar mem helpers as global
- Flat scratch cannot be an atomic
This was tested using a modified version of the 'square' application:
template <typename T>
__global__ void
scratch_square(T *C_d, T *A_d, size_t N)
{
size_t offset = (blockIdx.x * blockDim.x + threadIdx.x);
size_t stride = blockDim.x * gridDim.x ;
volatile int foo; // Volatile ensures scratch / unoptimized code
for (size_t i=offset; i<N; i+=stride) {
foo = A_d[i];
C_d[i] = foo * foo;
}
}
Change-Id: Icc91a7f67836fa3e759fefe7c1c3f6851528ae7d
60f071d09a