DXIL Disassembly prefix phi SSA with the block

Highlight that the SSA value used as the phi result is captured from the block branched from, not the SSA value in the current block

i.e.
_label7:                      // preceded by _label9, _label6
  float _375 = phi float [ _label9::_404, _label9 ], [ 1.00000, _label6 ];
  float _376 = phi float [ _label9::_375, _label9 ], [ 1.00000, _label6 ];

renderdoc/driver/shaders/dxil/dxil_disassemble.cpp

@@ -4641,8 +4641,11 @@ void Program::MakeRDDisassemblyString(const DXBC::Reflection *reflection)
                 lineStr += " ";
               else
                 lineStr += ", ";
-              lineStr += StringFormat::Fmt("[ %s, %s ]", GetArgId(inst, a).c_str(),
-                                           GetArgId(inst, a + 1).c_str());
+              rdcstr block = GetArgId(inst, a + 1);
+              lineStr += "[ ";
+              if(IsSSA(inst.args[a]))
+                lineStr += StringFormat::Fmt("%s::", block.c_str());
+              lineStr += StringFormat::Fmt("%s, %s ]", GetArgId(inst, a).c_str(), block.c_str());
             }
             break;
           }