commit 5f28475b30cf09e946bf6cb7c8de6d597a41610e
author Duncan Sands <baldrick@free.fr> Sun Oct 24 12:23:30 2010 +0000
committer Duncan Sands <baldrick@free.fr> Sun Oct 24 12:23:30 2010 +0000
tree 0f56958d9b7aada7cb44ded00547823c403fc43a
parent c052a8c772b1d55e5ed1a34f1750dac20c66c641

Fix PR8445: a block with no predecessors may be the entry block, in which case
it isn't unreachable and should not be zapped.  The check for the entry block
was missing in one case: a block containing a unwind instruction.  While there,
do some small cleanups: "M" is not a great name for a Function* (it would be
more appropriate for a Module*), change it to "Fn"; use Fn in more places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117224 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyCFG.cpp

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 28d7afb..de1f12e 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1720,15 +1720,14 @@
 
 bool SimplifyCFGOpt::run(BasicBlock *BB) {
   bool Changed = false;
-  Function *M = BB->getParent();
+  Function *Fn = BB->getParent();
 
-  assert(BB && BB->getParent() && "Block not embedded in function!");
+  assert(BB && Fn && "Block not embedded in function!");
   assert(BB->getTerminator() && "Degenerate basic block encountered!");
 
   // Remove basic blocks that have no predecessors (except the entry block)...
   // or that just have themself as a predecessor.  These are unreachable.
-  if ((pred_begin(BB) == pred_end(BB) &&
-       &BB->getParent()->getEntryBlock() != BB) ||
+  if ((pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) ||
       BB->getSinglePredecessor() == BB) {
     DEBUG(dbgs() << "Removing BB: \n" << *BB);
     DeleteDeadBlock(BB);
@@ -1798,7 +1797,7 @@
         // If we eliminated all predecessors of the block, delete the block now.
         if (pred_begin(BB) == pred_end(BB))
           // We know there are no successors, so just nuke the block.
-          M->getBasicBlockList().erase(BB);
+          Fn->getBasicBlockList().erase(BB);
 
         return true;
       }
@@ -1847,10 +1846,10 @@
       Preds.pop_back();
     }
 
-    // If this block is now dead, remove it.
-    if (pred_begin(BB) == pred_end(BB)) {
+    // If this block is now dead (and isn't the entry block), remove it.
+    if (pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) {
       // We know there are no successors, so just nuke the block.
-      M->getBasicBlockList().erase(BB);
+      Fn->getBasicBlockList().erase(BB);
       return true;
     }
 
@@ -1880,7 +1879,7 @@
       while (isa<DbgInfoIntrinsic>(BBI))
         ++BBI;
       if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
-        if (BB != &BB->getParent()->getEntryBlock())
+        if (BB != &Fn->getEntryBlock())
           if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
             return true;
       
@@ -2050,10 +2049,9 @@
       }
 
       // If this block is now dead, remove it.
-      if (pred_begin(BB) == pred_end(BB) &&
-          BB != &BB->getParent()->getEntryBlock()) {
+      if (pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) {
         // We know there are no successors, so just nuke the block.
-        M->getBasicBlockList().erase(BB);
+        Fn->getBasicBlockList().erase(BB);
         return true;
       }
     }