shader: Initial recompiler work

src/shader_recompiler/ir_opt/identity_removal_pass.cpp

@@ -0,0 +1,37 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <vector>
+
+#include "shader_recompiler/frontend/ir/basic_block.h"
+#include "shader_recompiler/frontend/ir/microinstruction.h"
+#include "shader_recompiler/ir_opt/passes.h"
+
+namespace Shader::Optimization {
+
+void IdentityRemovalPass(IR::Block& block) {
+    std::vector<IR::Inst*> to_invalidate;
+
+    for (auto inst = block.begin(); inst != block.end();) {
+        const size_t num_args{inst->NumArgs()};
+        for (size_t i = 0; i < num_args; ++i) {
+            IR::Value arg;
+            while ((arg = inst->Arg(i)).IsIdentity()) {
+                inst->SetArg(i, arg.Inst()->Arg(0));
+            }
+        }
+        if (inst->Opcode() == IR::Opcode::Identity || inst->Opcode() == IR::Opcode::Void) {
+            to_invalidate.push_back(&*inst);
+            inst = block.Instructions().erase(inst);
+        } else {
+            ++inst;
+        }
+    }
+
+    for (IR::Inst* const inst : to_invalidate) {
+        inst->Invalidate();
+    }
+}
+
+} // namespace Shader::Optimization