From fb3b828158b2d41ab7434fdc8d96fe260a6b2a52 Mon Sep 17 00:00:00 2001
From: Merry <git@mary.rs>
Date: Fri, 22 Jul 2022 19:59:23 +0100
Subject: [PATCH] backend/arm64: Implement Identity

---
 src/dynarmic/backend/arm64/emit_arm64.cpp | 9 ++++-----
 src/dynarmic/backend/arm64/reg_alloc.cpp  | 6 ++++++
 src/dynarmic/backend/arm64/reg_alloc.h    | 2 ++
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/dynarmic/backend/arm64/emit_arm64.cpp b/src/dynarmic/backend/arm64/emit_arm64.cpp
index ee35945a..1195d29b 100644
--- a/src/dynarmic/backend/arm64/emit_arm64.cpp
+++ b/src/dynarmic/backend/arm64/emit_arm64.cpp
@@ -24,11 +24,10 @@ template<>
 void EmitIR<IR::Opcode::Void>(oaknut::CodeGenerator&, EmitContext&, IR::Inst*) {}
 
 template<>
-void EmitIR<IR::Opcode::Identity>(oaknut::CodeGenerator& code, EmitContext& ctx, IR::Inst* inst) {
-    (void)code;
-    (void)ctx;
-    (void)inst;
-    ASSERT_FALSE("Unimplemented");
+void EmitIR<IR::Opcode::Identity>(oaknut::CodeGenerator&, EmitContext& ctx, IR::Inst* inst) {
+    auto args = ctx.reg_alloc.GetArgumentInfo(inst);
+
+    ctx.reg_alloc.DefineAsExisting(inst, args[0]);
 }
 
 template<>
diff --git a/src/dynarmic/backend/arm64/reg_alloc.cpp b/src/dynarmic/backend/arm64/reg_alloc.cpp
index f60d4faa..3cc12d4c 100644
--- a/src/dynarmic/backend/arm64/reg_alloc.cpp
+++ b/src/dynarmic/backend/arm64/reg_alloc.cpp
@@ -92,6 +92,12 @@ bool RegAlloc::IsValueLive(IR::Inst* inst) const {
     return !!ValueLocation(inst);
 }
 
+void RegAlloc::DefineAsExisting(IR::Inst* inst, Argument& arg) {
+    auto& info = ValueInfo(arg.value.GetInst());
+    info.values.emplace_back(inst);
+    info.expected_uses += inst->UseCount();
+}
+
 void RegAlloc::AssertNoMoreUses() const {
     const auto is_empty = [](const auto& i) { return i.values.empty() && !i.locked && !i.realized && !i.accumulated_uses && !i.expected_uses; };
     ASSERT(std::all_of(gprs.begin(), gprs.end(), is_empty));
diff --git a/src/dynarmic/backend/arm64/reg_alloc.h b/src/dynarmic/backend/arm64/reg_alloc.h
index b34d8059..864d8f56 100644
--- a/src/dynarmic/backend/arm64/reg_alloc.h
+++ b/src/dynarmic/backend/arm64/reg_alloc.h
@@ -204,6 +204,8 @@ public:
         }
     }
 
+    void DefineAsExisting(IR::Inst* inst, Argument& arg);
+
     void SpillFlags();
     void SpillAll();