shader: switch canonicalization: fix ordering

rpcsx/gpu/lib/gcn-shader/src/transform/transformations.cpp

@@ -2,6 +2,7 @@
 #include "SpvConverter.hpp"
 #include "analyze.hpp"
 #include "dialect.hpp"
+#include <algorithm>
 #include <list>
 #include <rx/die.hpp>
 
@@ -316,6 +317,7 @@ toCanonicalSwitchSelectionConstruct(spv::Context &context,
     return;
   }
 
+  {
     std::vector<ir::Block> workList;
 
     for (auto &[target, caseInfo] : cases) {
@@ -345,32 +347,31 @@ toCanonicalSwitchSelectionConstruct(spv::Context &context,
         }
       }
     }
+  }
 
   std::list<ir::Block> sortedCases;
+  std::list<std::pair<ir::Block, ir::Block>> workList;
 
   for (auto &[target, caseInfo] : cases) {
     if (caseInfo.fallthroughBlock == nullptr) {
       sortedCases.push_back(target);
+    } else {
+      workList.emplace_back(target, caseInfo.fallthroughBlock);
     }
   }
 
   assert(!sortedCases.empty());
 
-  for (auto &[target, caseInfo] : cases) {
-    if (caseInfo.fallthroughBlock == nullptr) {
-      continue;
-    }
+  while (!workList.empty()) {
+    auto [block, fallthroughBlock] = workList.front();
+    workList.pop_front();
 
-    auto it = sortedCases.begin();
-    while (it != sortedCases.end()) {
-      if (caseInfo.fallthroughBlock == *it) {
-        break;
+    if (auto it = std::ranges::find(sortedCases, fallthroughBlock);
+        it != sortedCases.end()) {
+      sortedCases.insert(it, block);
+    } else {
+      workList.emplace_back(block, fallthroughBlock);
     }
-
-      ++it;
-    }
-
-    sortedCases.insert(it, target);
   }
 
   for (auto target : sortedCases) {