4 files changed, 32 insertions, 0 deletions

diff --git a/src/shader_recompiler/frontend/ir/microinstruction.cpp b/src/shader_recompiler/frontend/ir/microinstruction.cpp
index 5c1b02d53..dba902186 100644
--- a/src/shader_recompiler/frontend/ir/microinstruction.cpp
+++ b/src/shader_recompiler/frontend/ir/microinstruction.cpp
@@ -61,6 +61,7 @@ bool Inst::MayHaveSideEffects() const noexcept {
     case Opcode::LoopMerge:
     case Opcode::SelectionMerge:
     case Opcode::Return:
+    case Opcode::Join:
     case Opcode::Unreachable:
     case Opcode::DemoteToHelperInvocation:
     case Opcode::Barrier:
diff --git a/src/shader_recompiler/frontend/ir/opcodes.inc b/src/shader_recompiler/frontend/ir/opcodes.inc
index 8f32c9e74..b14719c51 100644
--- a/src/shader_recompiler/frontend/ir/opcodes.inc
+++ b/src/shader_recompiler/frontend/ir/opcodes.inc
@@ -13,6 +13,7 @@ OPCODE(BranchConditional,                                   Void,           U1,
 OPCODE(LoopMerge,                                           Void,           Label,          Label,                                                          )
 OPCODE(SelectionMerge,                                      Void,           Label,                                                                          )
 OPCODE(Return,                                              Void,                                                                                           )
+OPCODE(Join,                                                Void,                                                                                           )
 OPCODE(Unreachable,                                         Void,                                                                                           )
 OPCODE(DemoteToHelperInvocation,                            Void,           Label,                                                                          )
 
diff --git a/src/shader_recompiler/frontend/maxwell/program.cpp b/src/shader_recompiler/frontend/maxwell/program.cpp
index aee96eae3..59897cb3e 100644
--- a/src/shader_recompiler/frontend/maxwell/program.cpp
+++ b/src/shader_recompiler/frontend/maxwell/program.cpp
@@ -150,4 +150,32 @@ IR::Program TranslateProgram(ObjectPool<IR::Inst>& inst_pool, ObjectPool<IR::Blo
     return program;
 }
 
+IR::Program MergeDualVertexPrograms(IR::Program& vertex_a, IR::Program& vertex_b,
+                                    Environment& env2) {
+    IR::Program program{};
+    Optimization::VertexATransformPass(vertex_a);
+    Optimization::VertexBTransformPass(vertex_b);
+    program.blocks.swap(vertex_a.blocks);
+    for (IR::Block* block : vertex_b.blocks) {
+        program.blocks.push_back(block);
+    }
+    program.stage = Stage::VertexB;
+    program.info = vertex_a.info;
+    program.local_memory_size = std::max(vertex_a.local_memory_size, vertex_b.local_memory_size);
+
+    for (size_t index = 0; index < 32; index++) {
+        program.info.input_generics[index].used |= vertex_b.info.input_generics[index].used;
+        program.info.stores_generics[index] |= vertex_b.info.stores_generics[index];
+    }
+    Optimization::JoinTextureInfo(program.info, vertex_b.info);
+    Optimization::JoinStorageInfo(program.info, vertex_b.info);
+    Optimization::DualVertexJoinPass(program);
+    program.post_order_blocks = PostOrder(program.blocks);
+    Optimization::DeadCodeEliminationPass(program);
+    Optimization::IdentityRemovalPass(program);
+    Optimization::VerificationPass(program);
+    Optimization::CollectShaderInfoPass(env2, program);
+    return program;
+}
+
 } // namespace Shader::Maxwell
diff --git a/src/shader_recompiler/frontend/maxwell/program.h b/src/shader_recompiler/frontend/maxwell/program.h
index 542621a1d..6e5d5ddd0 100644
--- a/src/shader_recompiler/frontend/maxwell/program.h
+++ b/src/shader_recompiler/frontend/maxwell/program.h
@@ -21,4 +21,6 @@ namespace Shader::Maxwell {
                                            ObjectPool<IR::Block>& block_pool, Environment& env,
                                            Flow::CFG& cfg);
 
+[[nodiscard]] IR::Program MergeDualVertexPrograms(IR::Program& vertex_a, IR::Program& vertex_b,
+                                                  Environment& env_vertex_b);
 } // namespace Shader::Maxwell