Fix what is _hopefully_ the last corner case for loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40503 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 92 insertions, 2 deletions

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index f3aa796..d7e6228 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -738,8 +738,12 @@ Value *GVN::performPHIConstruction(BasicBlock *BB, LoadInst* orig,
     for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
       if (!visited.count(*PI))
         PN->addIncoming(performPHIConstruction(*PI, orig, Phis, visited), *PI);
-      else
-        PN->addIncoming(Phis[*PI], *PI);
+      else {
+        if (Phis[*PI])
+          PN->addIncoming(Phis[*PI], *PI);
+        else
+          PN->addIncoming(PN, *PI);
+      }
     visited.erase(BB);
     
     bool all_same = PN->getNumIncomingValues() != 1;
diff --git a/test/Transforms/GVN/2007-07-25-DominatedLoop.ll b/test/Transforms/GVN/2007-07-25-DominatedLoop.ll
new file mode 100644
index 0000000..7c10f97
--- /dev/null
+++ b/test/Transforms/GVN/2007-07-25-DominatedLoop.ll
@@ -0,0 +1,86 @@
+; RUN: llvm-as < %s | opt -gvn | llvm-dis
+
+	%struct.PerlInterpreter = type { i8 }
+@PL_sv_count = external global i32		; <i32*> [#uses=2]
+
+define void @perl_destruct(%struct.PerlInterpreter* %sv_interp) {
+entry:
+	br i1 false, label %cond_next25, label %cond_true16
+
+cond_true16:		; preds = %entry
+	ret void
+
+cond_next25:		; preds = %entry
+	br i1 false, label %cond_next33, label %cond_true32
+
+cond_true32:		; preds = %cond_next25
+	ret void
+
+cond_next33:		; preds = %cond_next25
+	br i1 false, label %cond_next61, label %cond_true.i46
+
+cond_true.i46:		; preds = %cond_next33
+	ret void
+
+cond_next61:		; preds = %cond_next33
+	br i1 false, label %cond_next69, label %cond_true66
+
+cond_true66:		; preds = %cond_next61
+	ret void
+
+cond_next69:		; preds = %cond_next61
+	br i1 false, label %Perl_safefree.exit52, label %cond_true.i50
+
+cond_true.i50:		; preds = %cond_next69
+	ret void
+
+Perl_safefree.exit52:		; preds = %cond_next69
+	br i1 false, label %cond_next80, label %cond_true77
+
+cond_true77:		; preds = %Perl_safefree.exit52
+	ret void
+
+cond_next80:		; preds = %Perl_safefree.exit52
+	br i1 false, label %Perl_safefree.exit56, label %cond_true.i54
+
+cond_true.i54:		; preds = %cond_next80
+	ret void
+
+Perl_safefree.exit56:		; preds = %cond_next80
+	br i1 false, label %Perl_safefree.exit60, label %cond_true.i58
+
+cond_true.i58:		; preds = %Perl_safefree.exit56
+	ret void
+
+Perl_safefree.exit60:		; preds = %Perl_safefree.exit56
+	br i1 false, label %Perl_safefree.exit64, label %cond_true.i62
+
+cond_true.i62:		; preds = %Perl_safefree.exit60
+	ret void
+
+Perl_safefree.exit64:		; preds = %Perl_safefree.exit60
+	br i1 false, label %Perl_safefree.exit68, label %cond_true.i66
+
+cond_true.i66:		; preds = %Perl_safefree.exit64
+	ret void
+
+Perl_safefree.exit68:		; preds = %Perl_safefree.exit64
+	br i1 false, label %cond_next150, label %cond_true23.i
+
+cond_true23.i:		; preds = %Perl_safefree.exit68
+	ret void
+
+cond_next150:		; preds = %Perl_safefree.exit68
+	%tmp16092 = load i32* @PL_sv_count, align 4		; <i32> [#uses=0]
+	br label %cond_next165
+
+bb157:		; preds = %cond_next165
+	%tmp158 = load i32* @PL_sv_count, align 4		; <i32> [#uses=0]
+	br label %cond_next165
+
+cond_next165:		; preds = %bb157, %cond_next150
+	br i1 false, label %bb171, label %bb157
+
+bb171:		; preds = %cond_next165
+	ret void
+}