From 996d5cb841490f650a43847faad5d04e671bc1bb Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Mon, 20 Apr 2020 16:12:19 +0100
Subject: [PATCH] ir_opt: Add IdentityRemovalPass

---
 src/CMakeLists.txt                   |  1 +
 src/ir_opt/identity_removal_pass.cpp | 46 ++++++++++++++++++++++++++++
 src/ir_opt/passes.h                  |  3 +-
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 src/ir_opt/identity_removal_pass.cpp

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9f5b45b4..68dfb6cd 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -95,6 +95,7 @@ add_library(dynarmic
     frontend/ir/value.h
     ir_opt/constant_propagation_pass.cpp
     ir_opt/dead_code_elimination_pass.cpp
+    ir_opt/identity_removal_pass.cpp
     ir_opt/passes.h
     ir_opt/verification_pass.cpp
 )
diff --git a/src/ir_opt/identity_removal_pass.cpp b/src/ir_opt/identity_removal_pass.cpp
new file mode 100644
index 00000000..1d744b48
--- /dev/null
+++ b/src/ir_opt/identity_removal_pass.cpp
@@ -0,0 +1,46 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2020 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#include <vector>
+
+#include "common/iterator_util.h"
+#include "frontend/ir/basic_block.h"
+#include "frontend/ir/opcodes.h"
+#include "ir_opt/passes.h"
+
+namespace Dynarmic::Optimization {
+
+void IdentityRemovalPass(IR::Block& block) {
+    std::vector<IR::Inst*> to_invalidate;
+
+    auto iter = block.begin();
+    while (iter != block.end()) {
+        IR::Inst& inst = *iter;
+
+        const size_t num_args = inst.NumArgs();
+        for (size_t i = 0; i < num_args; i++) {
+            while (true) {
+                IR::Value arg = inst.GetArg(i);
+                if (!arg.IsIdentity())
+                    break;
+                inst.SetArg(i, arg.GetInst()->GetArg(0));
+            }
+        }
+
+        if (inst.GetOpcode() == IR::Opcode::Identity) {
+            iter = block.Instructions().erase(inst);
+            to_invalidate.push_back(&inst);
+        } else {
+            ++iter;
+        }
+    }
+
+    for (IR::Inst* inst : to_invalidate) {
+        inst->Invalidate();
+    }
+}
+
+} // namespace Dynarmic
diff --git a/src/ir_opt/passes.h b/src/ir_opt/passes.h
index 835f3aad..94e389a2 100644
--- a/src/ir_opt/passes.h
+++ b/src/ir_opt/passes.h
@@ -21,13 +21,14 @@ class Block;
 
 namespace Dynarmic::Optimization {
 
-void A32GetSetElimination(IR::Block& block);
 void A32ConstantMemoryReads(IR::Block& block, A32::UserCallbacks* cb);
+void A32GetSetElimination(IR::Block& block);
 void A64CallbackConfigPass(IR::Block& block, const A64::UserConfig& conf);
 void A64GetSetElimination(IR::Block& block);
 void A64MergeInterpretBlocksPass(IR::Block& block, A64::UserCallbacks* cb);
 void ConstantPropagation(IR::Block& block);
 void DeadCodeElimination(IR::Block& block);
+void IdentityRemovalPass(IR::Block& block);
 void VerificationPass(const IR::Block& block);
 
 } // namespace Dynarmic::Optimization