block_of_code: Fix running under Rosetta

Rosetta doesn't have accurate emulation of the sahf instruction

src/dynarmic/backend/x64/block_of_code.cpp

@@ -12,6 +12,12 @@
 #    include <sys/mman.h>
 #endif
 
+#ifdef __APPLE__
+#    include <errno.h>
+#    include <fmt/format.h>
+#    include <sys/sysctl.h>
+#endif
+
 #include <array>
 #include <cstring>
 
@@ -183,6 +189,19 @@ HostFeature GetHostFeatures() {
     return features;
 }
 
+#ifdef __APPLE__
+bool IsUnderRosetta() {
+    int result = 0;
+    size_t result_size = sizeof(result);
+    if (sysctlbyname("sysctl.proc_translated", &result, &result_size, nullptr, 0) == -1) {
+        if (errno != ENOENT)
+            fmt::print("IsUnderRosetta: Failed to detect Rosetta state, assuming not under Rosetta");
+        return false;
+    }
+    return result != 0;
+}
+#endif
+
 }  // anonymous namespace
 
 BlockOfCode::BlockOfCode(RunCodeCallbacks cb, JitStateInfo jsi, size_t total_code_size, std::function<void(BlockOfCode&)> rcp)
@@ -394,6 +413,10 @@ void BlockOfCode::LookupBlock() {
 }
 
 void BlockOfCode::LoadRequiredFlagsForCondFromRax(IR::Cond cond) {
+#ifdef __APPLE__
+    static const bool is_rosetta = IsUnderRosetta();
+#endif
+
     // sahf restores SF, ZF, CF
     // add al, 0x7F restores OF
 
@@ -419,6 +442,15 @@ void BlockOfCode::LoadRequiredFlagsForCondFromRax(IR::Cond cond) {
     case IR::Cond::LT:  // n != v
     case IR::Cond::GT:  // !z & (n == v)
     case IR::Cond::LE:  // z | (n != v)
+#ifdef __APPLE__
+        if (is_rosetta) {
+            shl(al, 3);
+            xchg(al, ah);
+            push(rax);
+            popf();
+            break;
+        }
+#endif
         cmp(al, 0x81);
         sahf();
         break;