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

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 28d7afbf1c33e03be239bc539d8a4e33b1c10abc..de1f12ec1b72d107963893486b0d730c0d8e8282 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1720,15 +1720,14 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
 
 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 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
         // 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 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
       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 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
       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 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
       }
 
       // 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;
       }
     }

diff --git a/test/Transforms/SimplifyCFG/2010-10-24-OnlyUnwindInEntry.ll b/test/Transforms/SimplifyCFG/2010-10-24-OnlyUnwindInEntry.ll
new file mode 100644 (file)
index 0000000..ebacf2f
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/2010-10-24-OnlyUnwindInEntry.ll
@@ -0,0 +1,6 @@
+; RUN: opt %s -simplifycfg -disable-output
+; PR8445
+
+define void @test() {
+      unwind
+}