2 files changed, 18 insertions, 0 deletions

diff --git a/src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp b/src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp
index 73b67f0af..e4802bf9e 100644
--- a/src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp
+++ b/src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp
@@ -339,6 +339,10 @@ Id EmitGetAttribute(EmitContext& ctx, IR::Attribute attr, Id vertex) {
             const Id base{ctx.OpLoad(ctx.U32[1], ctx.base_vertex)};
             return ctx.OpBitcast(ctx.F32[1], ctx.OpISub(ctx.U32[1], index, base));
         }
+    case IR::Attribute::BaseInstance:
+        return ctx.OpBitcast(ctx.F32[1], ctx.OpLoad(ctx.U32[1], ctx.base_instance));
+    case IR::Attribute::BaseVertex:
+        return ctx.OpBitcast(ctx.F32[1], ctx.OpLoad(ctx.U32[1], ctx.base_vertex));
     case IR::Attribute::FrontFace:
         return ctx.OpSelect(ctx.F32[1], ctx.OpLoad(ctx.U1, ctx.front_face),
                             ctx.OpBitcast(ctx.F32[1], ctx.Const(std::numeric_limits<u32>::max())),
@@ -380,6 +384,10 @@ Id EmitGetAttributeU32(EmitContext& ctx, IR::Attribute attr, Id) {
             const Id base{ctx.OpLoad(ctx.U32[1], ctx.base_vertex)};
             return ctx.OpISub(ctx.U32[1], index, base);
         }
+    case IR::Attribute::BaseInstance:
+        return ctx.OpLoad(ctx.U32[1], ctx.base_instance);
+    case IR::Attribute::BaseVertex:
+        return ctx.OpLoad(ctx.U32[1], ctx.base_vertex);
     default:
         throw NotImplementedException("Read U32 attribute {}", attr);
     }
diff --git a/src/shader_recompiler/backend/spirv/spirv_emit_context.cpp b/src/shader_recompiler/backend/spirv/spirv_emit_context.cpp
index 41dc6d031..563a5fc49 100644
--- a/src/shader_recompiler/backend/spirv/spirv_emit_context.cpp
+++ b/src/shader_recompiler/backend/spirv/spirv_emit_context.cpp
@@ -1379,18 +1379,28 @@ void EmitContext::DefineInputs(const IR::Program& program) {
     if (loads[IR::Attribute::InstanceId]) {
         if (profile.support_vertex_instance_id) {
             instance_id = DefineInput(*this, U32[1], true, spv::BuiltIn::InstanceId);
+            if (loads[IR::Attribute::BaseInstance]) {
+                base_instance = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseVertex);
+            }
         } else {
             instance_index = DefineInput(*this, U32[1], true, spv::BuiltIn::InstanceIndex);
             base_instance = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseInstance);
         }
+    } else if (loads[IR::Attribute::BaseInstance]) {
+        base_instance = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseInstance);
     }
     if (loads[IR::Attribute::VertexId]) {
         if (profile.support_vertex_instance_id) {
             vertex_id = DefineInput(*this, U32[1], true, spv::BuiltIn::VertexId);
+            if (loads[IR::Attribute::BaseVertex]) {
+                base_vertex = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseVertex);
+            }
         } else {
             vertex_index = DefineInput(*this, U32[1], true, spv::BuiltIn::VertexIndex);
             base_vertex = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseVertex);
         }
+    } else if (loads[IR::Attribute::BaseVertex]) {
+        base_vertex = DefineInput(*this, U32[1], true, spv::BuiltIn::BaseVertex);
     }
     if (loads[IR::Attribute::FrontFace]) {
         front_face = DefineInput(*this, U1, true, spv::BuiltIn::FrontFacing);