Fix simplifycfg crash in handing block merge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55971 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 71 insertions, 1 deletions

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 719bc8a34f..a98e1356ad 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -54,7 +54,17 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
   
   // Can't merge if there are multiple successors.
   if (!OnlySucc) return false;
-  
+
+  // Can't merge if there is PHI loop.
+  for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
+    if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+        if (PN->getIncomingValue(i) == PN)
+          return false;
+    } else
+      break;
+  }
+
   // Begin by getting rid of unneeded PHIs.
   while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
     PN->replaceAllUsesWith(PN->getIncomingValue(0));
diff --git a/test/Transforms/SimplifyCFG/2008-09-08-MultiplePred.ll b/test/Transforms/SimplifyCFG/2008-09-08-MultiplePred.ll
new file mode 100644
index 0000000000..82a2cc0303
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/2008-09-08-MultiplePred.ll
@@ -0,0 +1,60 @@
+; RUN: llvm-as < %s | opt -simplifycfg -disable-output
+; PR 2777
+@g_103 = common global i32 0		; <i32*> [#uses=1]
+
+define i32 @func_127(i32 %p_129) nounwind {
+entry:
+	load i32* @g_103, align 4		; <i32>:0 [#uses=1]
+	icmp eq i32 %0, 0		; <i1>:1 [#uses=2]
+	br i1 %1, label %bb6.preheader, label %entry.return_crit_edge
+
+entry.return_crit_edge:		; preds = %entry
+	br label %return
+
+bb6.preheader:		; preds = %entry
+	br i1 %1, label %bb6.preheader.split.us, label %bb6.preheader.split
+
+bb6.preheader.split.us:		; preds = %bb6.preheader
+	br label %return.loopexit.split
+
+bb6.preheader.split:		; preds = %bb6.preheader
+	br label %bb6
+
+bb6:		; preds = %bb17.bb6_crit_edge, %bb6.preheader.split
+	%indvar35 = phi i32 [ 0, %bb6.preheader.split ], [ %indvar.next36, %bb17.bb6_crit_edge ]		; <i32> [#uses=1]
+	%p_129_addr.3.reg2mem.0 = phi i32 [ %p_129_addr.2, %bb17.bb6_crit_edge ], [ %p_129, %bb6.preheader.split ]		; <i32> [#uses=3]
+	icmp eq i32 %p_129_addr.3.reg2mem.0, 0		; <i1>:2 [#uses=1]
+	br i1 %2, label %bb6.bb17_crit_edge, label %bb8
+
+bb6.bb17_crit_edge:		; preds = %bb6
+	br label %bb17
+
+bb8:		; preds = %bb6
+	br label %bb13
+
+bb13:		; preds = %bb8
+	br label %bb17
+
+bb17:		; preds = %bb13, %bb6.bb17_crit_edge
+	%p_129_addr.2 = phi i32 [ %p_129_addr.3.reg2mem.0, %bb13 ], [ %p_129_addr.3.reg2mem.0, %bb6.bb17_crit_edge ]		; <i32> [#uses=1]
+	%indvar.next36 = add i32 %indvar35, 1		; <i32> [#uses=2]
+	%exitcond37 = icmp eq i32 %indvar.next36, -1		; <i1> [#uses=1]
+	br i1 %exitcond37, label %return.loopexit, label %bb17.bb6_crit_edge
+
+bb17.bb6_crit_edge:		; preds = %bb17
+	br label %bb6
+
+return.loopexit:		; preds = %bb17
+	br label %return.loopexit.split
+
+return.loopexit.split:		; preds = %return.loopexit, %bb6.preheader.split.us
+	br label %return
+
+return:		; preds = %return.loopexit.split, %entry.return_crit_edge
+	ret i32 1
+}
+
+define i32 @func_135(i8 zeroext %p_137, i32 %p_138, i32 %p_140) nounwind {
+entry:
+	ret i32 undef
+}