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[video,buffer] rewrite storagebufferbinding size() lambda to be full data driven instead of cbuf_index based (#4041)

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fixes an yxzx era bug where eden assumed NVN-style packed SSBO descriptors (u64 gpu_addr followed by size) only happen in cbuf_index == 0.

Mega Man Star Force Collection proves that assumption is false. It has an unbiased/global-memory SSBO descriptor in cbuf_index == 3, offsets 0x100/0x300, but the descriptor still appears to be { address, size }.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4041
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: crueter <crueter@eden-emu.dev>
This commit is contained in:
xbzk 2026-06-02 03:31:59 +02:00 • committed by crueter
parent 8fac95dcc0
commit 8e5419209c
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1 changed files with 9 additions and 15 deletions
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24
src/video_core/buffer_cache/buffer_cache.h
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@ -1893,23 +1893,17 @@ Binding BufferCache<P>::StorageBufferBinding(GPUVAddr ssbo_addr, u32 cbuf_index,
return NULL_BINDING;
}
// xbzk: New size logic. Fixes MCI.
// If ever the * comment below prove wrong, the 'if' block may be removed.
const auto size = [&]() {
const bool is_nvn_cbuf = cbuf_index == 0;
if (is_nvn_cbuf) {
// * The NVN driver buffer (index 0) is known to pack the SSBO address followed by its size.
const u64 next_qword = gpu_memory->Read<u64>(ssbo_addr + 8);
const u32 upper_32 = static_cast<u32>(next_qword >> 32);
// Hardware-based detection: GPU addresses have non-zero upper bits
if (upper_32 == 0) {
// This is a size field, not a GPU address
return static_cast<u32>(next_qword); // Return lower_32
}
const u32 memory_layout_size =
static_cast<u32>(gpu_memory->GetMemoryLayoutSize(gpu_addr));
const u64 next_qword = gpu_memory->Read<u64>(ssbo_addr + 8);
const u32 packed_size = static_cast<u32>(next_qword);
const bool next_qword_is_size = static_cast<u32>(next_qword >> 32) == 0 &&
packed_size != 0 &&
packed_size <= memory_layout_size;
if (next_qword_is_size) {
return packed_size;
}
// Fall through: either not NVN cbuf (Doom Eternal & +), or NVN but ssbo_addr+8 is a GPU address (MCI)
const u32 memory_layout_size = static_cast<u32>(gpu_memory->GetMemoryLayoutSize(gpu_addr));
// Cap at 8MB to prevent allocator overflow from misinterpreted addresses
return (std::min)(memory_layout_size, static_cast<u32>(8_MiB));
}();