Workaround clang/LLVM bug with /fp:fast+SSE+float_control (#449)

DDSTextureLoader/DDSTextureLoader12.cpp

@@ -830,6 +830,9 @@ namespace
 
                 // No 3:3:2 or paletted DXGI formats aka D3DFMT_R3G3B2, D3DFMT_P8
                 break;
+
+            default:
+                return DXGI_FORMAT_UNKNOWN;
             }
         }
         else if (ddpf.flags & DDS_LUMINANCE)
@@ -860,6 +863,9 @@ namespace
                     return DXGI_FORMAT_R8G8_UNORM; // Some DDS writers assume the bitcount should be 8 instead of 16
                 }
                 break;
+
+            default:
+                return DXGI_FORMAT_UNKNOWN;
             }
         }
         else if (ddpf.flags & DDS_ALPHA)
@@ -892,6 +898,9 @@ namespace
                     return DXGI_FORMAT_R8G8_SNORM; // D3DX10/11 writes this out as DX10 extension
                 }
                 break;
+
+            default:
+                return DXGI_FORMAT_UNKNOWN;
             }
 
             // No DXGI format maps to DDPF_BUMPLUMINANCE aka D3DFMT_L6V5U5, D3DFMT_X8L8V8U8
@@ -992,6 +1001,9 @@ namespace
                 return DXGI_FORMAT_R32G32B32A32_FLOAT;
 
             // No DXGI format maps to D3DFMT_CxV8U8
+
+            default:
+                return DXGI_FORMAT_UNKNOWN;
             }
         }
 
@@ -1127,6 +1139,9 @@ namespace
                 res.SlicePitch = res.RowPitch * static_cast<LONG>(height);
             }
             break;
+
+        default:
+            break;
         }
     }