[dxbc] Use SSBOs for dynamically indexed constant buffers if needed

SSBOs are tightly bound-checked on all Nvidia GPUs, so this allows for
a more accurate workaround for games relying on OOB access behaviour.

src/d3d11/d3d11_buffer.cpp

@@ -34,7 +34,8 @@ namespace dxvk {
     }
     
     if (pDesc->BindFlags & D3D11_BIND_CONSTANT_BUFFER) {
-      info.usage  |= VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT;
+      info.usage  |= VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT
+                  |  VK_BUFFER_USAGE_STORAGE_BUFFER_BIT;
       info.stages |= m_device->GetEnabledShaderStages();
       info.access |= VK_ACCESS_UNIFORM_READ_BIT;
     }

src/dxbc/dxbc_compiler.cpp

@@ -755,16 +755,20 @@ namespace dxvk {
     //    (1) Number of constants in the buffer
     const uint32_t bufferId     = ins.dst[0].idx[0].offset;
     const uint32_t elementCount = ins.dst[0].idx[1].offset;
+
+    bool asSsbo = m_moduleInfo.options.dynamicIndexedConstantBufferAsSsbo
+      && ins.controls.accessType() == DxbcConstantBufferAccessType::DynamicallyIndexed;
     
     this->emitDclConstantBufferVar(bufferId, elementCount,
-      str::format("cb", bufferId).c_str());
+      str::format("cb", bufferId).c_str(), asSsbo);
   }
   
   
   void DxbcCompiler::emitDclConstantBufferVar(
           uint32_t                regIdx,
           uint32_t                numConstants,
-    const char*                   name) {
+    const char*                   name,
+          bool                    asSsbo) {
     // Uniform buffer data is stored as a fixed-size array
     // of 4x32-bit vectors. SPIR-V requires explicit strides.
     const uint32_t arrayType = m_module.defArrayTypeUnique(
@@ -776,7 +780,9 @@ namespace dxvk {
     // struct and decorate that struct as a block.
     const uint32_t structType = m_module.defStructTypeUnique(1, &arrayType);
     
-    m_module.decorateBlock       (structType);
+    m_module.decorate(structType, asSsbo
+      ? spv::DecorationBufferBlock
+      : spv::DecorationBlock);
     m_module.memberDecorateOffset(structType, 0, 0);
     
     m_module.setDebugName        (structType, str::format(name, "_t").c_str());
@@ -796,7 +802,10 @@ namespace dxvk {
     
     m_module.decorateDescriptorSet(varId, 0);
     m_module.decorateBinding(varId, bindingId);
-    
+
+    if (asSsbo)
+      m_module.decorate(varId, spv::DecorationNonWritable);
+
     // Declare a specialization constant which will
     // store whether or not the resource is bound.
     const uint32_t specConstId = m_module.specConstBool(true);
@@ -813,7 +822,9 @@ namespace dxvk {
     // Store descriptor info for the shader interface
     DxvkResourceSlot resource;
     resource.slot = bindingId;
-    resource.type = VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER;
+    resource.type = asSsbo
+      ? VK_DESCRIPTOR_TYPE_STORAGE_BUFFER
+      : VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER;
     resource.view = VK_IMAGE_VIEW_TYPE_MAX_ENUM;
     resource.access = VK_ACCESS_UNIFORM_READ_BIT;
     m_resourceSlots.push_back(resource);
@@ -1505,7 +1516,8 @@ namespace dxvk {
   void DxbcCompiler::emitDclImmediateConstantBufferUbo(
           uint32_t                dwordCount,
     const uint32_t*               dwordArray) {
-    this->emitDclConstantBufferVar(Icb_BindingSlotId, dwordCount / 4, "icb");
+    this->emitDclConstantBufferVar(Icb_BindingSlotId, dwordCount / 4, "icb",
+      m_moduleInfo.options.dynamicIndexedConstantBufferAsSsbo);
     m_immConstData = DxvkShaderConstData(dwordCount, dwordArray);
   }
 

src/dxbc/dxbc_compiler.h

@@ -575,7 +575,8 @@ namespace dxvk {
     void emitDclConstantBufferVar(
             uint32_t                regIdx,
             uint32_t                numConstants,
-      const char*                   name);
+      const char*                   name,
+            bool                    asSsbo);
     
     void emitDclSampler(
       const DxbcShaderInstruction&  ins);

src/dxbc/dxbc_options.cpp

@@ -41,7 +41,7 @@ namespace dxvk {
     zeroInitWorkgroupMemory  = options.zeroInitWorkgroupMemory;
 
     if (DxvkGpuVendor(devInfo.core.properties.vendorID) != DxvkGpuVendor::Amd)
-      constantBufferRangeCheck = options.constantBufferRangeCheck;
+      dynamicIndexedConstantBufferAsSsbo = options.constantBufferRangeCheck;
     
     // Disable early discard on RADV (with LLVM) due to GPU hangs
     // Disable early discard on Nvidia because it may hurt performance

src/dxbc/dxbc_options.h

@@ -39,6 +39,10 @@ namespace dxvk {
     // Fixes issues in some games, breaks others.
     bool constantBufferRangeCheck = false;
 
+    /// Implement dynamically indexed uniform buffers
+    /// with storage buffers for tight bounds checking
+    bool dynamicIndexedConstantBufferAsSsbo = false;
+
     /// Clear thread-group shared memory to zero
     bool zeroInitWorkgroupMemory = false;