From 6c4fa780e078705c1d8b44dc894b3ead1d07bd03 Mon Sep 17 00:00:00 2001
From: merry <git@mary.rs>
Date: Sun, 27 Feb 2022 19:54:35 +0000
Subject: [PATCH] {a32,a64}_emit_x64_memory: Ensure return value of fastmem
 callback are zero-extended

---
 .../backend/x64/a32_emit_x64_memory.cpp        |  1 +
 .../backend/x64/a64_emit_x64_memory.cpp        |  1 +
 src/dynarmic/backend/x64/block_of_code.h       | 18 ++++++++++++++++++
 3 files changed, 20 insertions(+)

diff --git a/src/dynarmic/backend/x64/a32_emit_x64_memory.cpp b/src/dynarmic/backend/x64/a32_emit_x64_memory.cpp
index e9c14725..35588758 100644
--- a/src/dynarmic/backend/x64/a32_emit_x64_memory.cpp
+++ b/src/dynarmic/backend/x64/a32_emit_x64_memory.cpp
@@ -53,6 +53,7 @@ void A32EmitX64::GenFastmemFallbacks() {
                     code.mov(Xbyak::Reg64{value_idx}, code.ABI_RETURN);
                 }
                 ABI_PopCallerSaveRegistersAndAdjustStackExcept(code, HostLocRegIdx(value_idx));
+                code.ZeroExtendFrom(bitsize, Xbyak::Reg64{value_idx});
                 code.ret();
                 PerfMapRegister(read_fallbacks[std::make_tuple(bitsize, vaddr_idx, value_idx)], code.getCurr(), fmt::format("a32_read_fallback_{}", bitsize));
             }
diff --git a/src/dynarmic/backend/x64/a64_emit_x64_memory.cpp b/src/dynarmic/backend/x64/a64_emit_x64_memory.cpp
index c472a7c1..d86bdf3f 100644
--- a/src/dynarmic/backend/x64/a64_emit_x64_memory.cpp
+++ b/src/dynarmic/backend/x64/a64_emit_x64_memory.cpp
@@ -141,6 +141,7 @@ void A64EmitX64::GenFastmemFallbacks() {
                     code.mov(Xbyak::Reg64{value_idx}, code.ABI_RETURN);
                 }
                 ABI_PopCallerSaveRegistersAndAdjustStackExcept(code, HostLocRegIdx(value_idx));
+                code.ZeroExtendFrom(bitsize, Xbyak::Reg64{value_idx});
                 code.ret();
                 PerfMapRegister(read_fallbacks[std::make_tuple(bitsize, vaddr_idx, value_idx)], code.getCurr(), fmt::format("a64_read_fallback_{}", bitsize));
             }
diff --git a/src/dynarmic/backend/x64/block_of_code.h b/src/dynarmic/backend/x64/block_of_code.h
index 97b8930a..17aa9cd7 100644
--- a/src/dynarmic/backend/x64/block_of_code.h
+++ b/src/dynarmic/backend/x64/block_of_code.h
@@ -96,6 +96,24 @@ public:
         CallFunction(Common::FptrCast(l));
     }
 
+    void ZeroExtendFrom(size_t bitsize, Xbyak::Reg64 reg) {
+        switch (bitsize) {
+        case 8:
+            movzx(reg.cvt32(), reg.cvt8());
+            return;
+        case 16:
+            movzx(reg.cvt32(), reg.cvt16());
+            return;
+        case 32:
+            mov(reg.cvt32(), reg.cvt32());
+            return;
+        case 64:
+            return;
+        default:
+            UNREACHABLE();
+        }
+    }
+
     Xbyak::Address MConst(const Xbyak::AddressFrame& frame, u64 lower, u64 upper = 0);
 
     /// Far code sits far away from the near code. Execution remains primarily in near code.