[clang] [clang][cleanup] simplify ReachableCode scanFromBlock (PR #72257)

[via cfe-commits]

https://github.com/thyecust created https://github.com/llvm/llvm-project/pull/72257

We can simplify this function and move some calculations out of loop.

>From 52b0204fec8394f9c2cfaeb3cc4f28e5d4c16170 Mon Sep 17 00:00:00 2001
From: thyecust <thy at mail.ecust.edu.cn>
Date: Tue, 14 Nov 2023 21:51:55 +0800
Subject: [PATCH] Update ReachableCode.cpp

---
 clang/lib/Analysis/ReachableCode.cpp | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index 1bf0d9aec8620e1..9c9e1a0fffb3c98 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -341,30 +341,27 @@ static unsigned scanFromBlock(const CFGBlock *Start,
     // This allows us to potentially uncover some "always unreachable" code
     // within the "sometimes unreachable" code.
     // Look at the successors and mark then reachable.
-    std::optional<bool> TreatAllSuccessorsAsReachable;
-    if (!IncludeSometimesUnreachableEdges)
+    bool TreatAllSuccessorsAsReachable;
+    if (IncludeSometimesUnreachableEdges) {
+      assert(PP);
+      TreatAllSuccessorsAsReachable =
+        shouldTreatSuccessorsAsReachable(item, *PP);
+    } else {
       TreatAllSuccessorsAsReachable = false;
+    }
 
     for (CFGBlock::const_succ_iterator I = item->succ_begin(),
          E = item->succ_end(); I != E; ++I) {
       const CFGBlock *B = *I;
-      if (!B) do {
+      if (!B) {
         const CFGBlock *UB = I->getPossiblyUnreachableBlock();
         if (!UB)
           break;
 
-        if (!TreatAllSuccessorsAsReachable) {
-          assert(PP);
-          TreatAllSuccessorsAsReachable =
-            shouldTreatSuccessorsAsReachable(item, *PP);
-        }
-
-        if (*TreatAllSuccessorsAsReachable) {
+        if (TreatAllSuccessorsAsReachable) {
           B = UB;
-          break;
         }
       }
-      while (false);
 
       if (B) {
         unsigned blockID = B->getBlockID();