[llvm] [AMDGPU] Improve StructurizeCFG pass performance: avoid redundant DebugLoc map initialization. NFC. (PR #130568)

[Juan Manuel Martinez Caamaño via llvm-commits]

================
@@ -990,10 +996,10 @@ BasicBlock *StructurizeCFG::getNextFlow(BasicBlock *Dominator) {
                                         Func, Insert);
   FlowSet.insert(Flow);
 
-  // use a temporary variable to avoid a use-after-free if the map's storage is
-  // reallocated
-  DebugLoc DL = TermDL[Dominator];
-  TermDL[Flow] = std::move(DL);
+  auto *Term = Dominator->getTerminator();
+  if (const DebugLoc &DL =
----------------
jmmartinez wrote:

We used to do a copy of the `DebugLoc` because the reference to `TermDL[Dominator]` could be invalidated if the underlying container reallocates a bigger array when we do `TermDL[Flow]`.

Could this issue still happen here? If yes, we would need to do a copy of the `DebugLoc`.

https://github.com/llvm/llvm-project/pull/130568