video_core: Small readback optimization (#3941)

* pm4_cmds: Handle nop packet overflow

* liverpool: Detect DispatchDirect patches and promote to DispatchIndirect

* clang..

* log removed

---------

Co-authored-by: georgemoralis <giorgosmrls@gmail.com>

src/video_core/amdgpu/liverpool.cpp

@@ -830,7 +830,14 @@ Liverpool::Task Liverpool::ProcessCompute(std::span<const u32> acb, u32 vqid) {
     FIBER_ENTER(acb_task_name[vqid]);
     auto& queue = asc_queues[{vqid}];
 
+    struct IndirectPatch {
+        const PM4Header* header;
+        VAddr indirect_addr;
+    };
+    boost::container::small_vector<IndirectPatch, 4> indirect_patches;
+
     auto base_addr = reinterpret_cast<VAddr>(acb.data());
+    size_t acb_size = acb.size_bytes();
     while (!acb.empty()) {
         ProcessCommands();
 
@@ -919,8 +926,18 @@ Liverpool::Task Liverpool::ProcessCompute(std::span<const u32> acb, u32 vqid) {
                         dma_data->src_sel == DmaDataSrc::MemoryUsingL2) &&
                        (dma_data->dst_sel == DmaDataDst::Memory ||
                         dma_data->dst_sel == DmaDataDst::MemoryUsingL2)) {
-                rasterizer->CopyBuffer(dma_data->DstAddress<VAddr>(), dma_data->SrcAddress<VAddr>(),
+                const u32 num_bytes = dma_data->NumBytes();
-                                       dma_data->NumBytes(), false, false);
+                const VAddr src_addr = dma_data->SrcAddress<VAddr>();
+                const VAddr dst_addr = dma_data->DstAddress<VAddr>();
+                const PM4Header* header =
+                    reinterpret_cast<const PM4Header*>(dst_addr - sizeof(PM4Header));
+                if (dst_addr >= base_addr && dst_addr < base_addr + acb_size &&
+                    num_bytes == sizeof(PM4CmdDispatchIndirect::GroupDimensions) &&
+                    header->type == 3 && header->type3.opcode == PM4ItOpcode::DispatchDirect) {
+                    indirect_patches.emplace_back(header, src_addr);
+                } else {
+                    rasterizer->CopyBuffer(dst_addr, src_addr, num_bytes, false, false);
+                }
             } else {
                 UNREACHABLE_MSG("WriteData src_sel = {}, dst_sel = {}",
                                 u32(dma_data->src_sel.Value()), u32(dma_data->dst_sel.Value()));
@@ -964,6 +981,12 @@ Liverpool::Task Liverpool::ProcessCompute(std::span<const u32> acb, u32 vqid) {
         }
         case PM4ItOpcode::DispatchDirect: {
             const auto* dispatch_direct = reinterpret_cast<const PM4CmdDispatchDirect*>(header);
+            if (auto it = std::ranges::find(indirect_patches, header, &IndirectPatch::header);
+                it != indirect_patches.end()) {
+                const auto size = sizeof(PM4CmdDispatchIndirect::GroupDimensions);
+                rasterizer->DispatchIndirect(it->indirect_addr, 0, size);
+                break;
+            }
             auto& cs_program = GetCsRegs();
             cs_program.dim_x = dispatch_direct->dim_x;
             cs_program.dim_y = dispatch_direct->dim_y;

src/video_core/amdgpu/pm4_cmds.h

@@ -50,7 +50,7 @@ union PM4Type3Header {
     }
 
     u32 NumWords() const {
-        return count + 1;
+        return (count + 1) & 0x3fff;
     }
 
     u32 raw;