From: Chris Lattner <sabre@nondot.org>
Date: Sat, 11 Dec 2004 05:32:19 +0000 (+0000)
Subject: Do not delete the entry block to a function.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=864737bf9e208566bbecb81dda9cce5245fa2bcf;p=oota-llvm.git

Do not delete the entry block to a function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18795 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 9a8d26bb7b8..7682e5a9e18 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1178,7 +1178,6 @@ bool IPSCCP::runOnModule(Module &M) {
       if (!ExecutableBBs.count(BB)) {
         DEBUG(std::cerr << "  BasicBlock Dead:" << *BB);
         ++IPNumDeadBlocks;
-        BlocksToErase.push_back(BB);
 
         // Delete the instructions backwards, as it has a reduced likelihood of
         // having to update as many def-use and use-def chains.
@@ -1206,6 +1205,11 @@ bool IPSCCP::runOnModule(Module &M) {
           TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
         BB->getInstList().erase(TI);
 
+        if (&*BB != &F->front())
+          BlocksToErase.push_back(BB);
+        else
+          new UnreachableInst(BB);
+
       } else {
         for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
           Instruction *Inst = BI++;