Silence some warnings

src/backend/Core.cpp

@@ -53,6 +53,7 @@ u32 Core::StepCPU() {
         return interpreter.ExecuteCached() + regs.PopStalledCycles();
 
     ircolib::panic("Invalid CPU type?");
+    return 0;
 }
 
 void Core::StepRSP(const u32 cpuCycles) {

src/backend/core/Mem.cpp

@@ -512,6 +512,7 @@ u8 Mem::BackupRead<u8>(const u32 addr) {
         }
     default:
         ircolib::panic("Backup read word with unknown save type");
+        return 0;
     }
 }
 

src/backend/core/mmio/PI.cpp

@@ -84,6 +84,7 @@ auto PI::BusRead<u8, true>(u32 addr) -> u8 {
     default:
         ircolib::panic("Should never end up here! Access to address {:08X} which did not match any PI bus regions!",
                        addr);
+        return 0;
     }
 }
 
@@ -129,6 +130,7 @@ auto PI::BusRead<u8, false>(u32 addr) -> u8 {
     default:
         ircolib::panic("Should never end up here! Access to address {:08X} which did not match any PI bus regions!",
                        addr);
+        return 0;
     }
 }
 
@@ -211,6 +213,7 @@ auto PI::BusRead<u16, false>(u32 addr) -> u16 {
     default:
         ircolib::panic("Should never end up here! Access to address {:08X} which did not match any PI bus regions!",
                        addr);
+        return 0;
     }
 }
 
@@ -302,6 +305,7 @@ auto PI::BusRead<u32, false>(u32 addr) -> u32 {
     default:
         ircolib::panic("Should never end up here! Access to address {:08X} which did not match any PI bus regions!",
                        addr);
+        return 0;
     }
 }
 
@@ -406,6 +410,7 @@ auto PI::BusRead<u64, false>(u32 addr) -> u64 {
     default:
         ircolib::panic("Should never end up here! Access to address {:08X} which did not match any PI bus regions!",
                        addr);
+        return 0;
     }
 }
 
@@ -485,6 +490,7 @@ auto PI::Read(u32 addr) const -> u32 {
         return piBsdDom2Rls;
     default:
         ircolib::panic("Unhandled PI[{:08X}] read", addr);
+        return 0;
     }
 }
 
@@ -499,6 +505,7 @@ u8 PI::GetDomain(const u32 address) {
         return 2;
     default:
         ircolib::panic("Unknown PI domain for address {:08X}!", address);
+        return 0;
     }
 }