[llvm-commits] [llvm] r104957 - in /llvm/trunk: lib/Analysis/Lint.cpp test/Other/lint.ll

[Dan Gohman]

Author: djg
Date: Fri May 28 11:45:33 2010
New Revision: 104957

URL: http://llvm.org/viewvc/llvm-project?rev=104957&view=rev
Log:
Detect self-referential values.

Modified:
    llvm/trunk/lib/Analysis/Lint.cpp
    llvm/trunk/test/Other/lint.ll

Modified: llvm/trunk/lib/Analysis/Lint.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Lint.cpp?rev=104957&r1=104956&r2=104957&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/Lint.cpp (original)
+++ llvm/trunk/lib/Analysis/Lint.cpp Fri May 28 11:45:33 2010
@@ -93,6 +93,8 @@
     void visitUnreachableInst(UnreachableInst &I);
 
     Value *findValue(Value *V, bool OffsetOk) const;
+    Value *findValueImpl(Value *V, bool OffsetOk,
+                         SmallPtrSet<Value *, 4> &Visited) const;
 
   public:
     Module *Mod;
@@ -498,6 +500,17 @@
 /// will simplify most of these kinds of things away. But it's a goal of
 /// this Lint pass to be useful even on non-optimized IR.
 Value *Lint::findValue(Value *V, bool OffsetOk) const {
+  SmallPtrSet<Value *, 4> Visited;
+  return findValueImpl(V, OffsetOk, Visited);
+}
+
+/// findValueImpl - Implementation helper for findValue.
+Value *Lint::findValueImpl(Value *V, bool OffsetOk,
+                           SmallPtrSet<Value *, 4> &Visited) const {
+  // Detect self-referential values.
+  if (!Visited.insert(V))
+    return UndefValue::get(V->getType());
+
   // TODO: Look through sext or zext cast, when the result is known to
   // be interpreted as signed or unsigned, respectively.
   // TODO: Look through calls with unique return values.
@@ -509,7 +522,7 @@
     for (;;) {
       if (Value *U = FindAvailableLoadedValue(L->getPointerOperand(),
                                               BB, BBI, 6, AA))
-        return findValue(U, OffsetOk);
+        return findValueImpl(U, OffsetOk, Visited);
       BB = L->getParent()->getUniquePredecessor();
       if (!BB) break;
       BBI = BB->end();
@@ -517,27 +530,27 @@
   } else if (CastInst *CI = dyn_cast<CastInst>(V)) {
     if (CI->isNoopCast(TD ? TD->getIntPtrType(V->getContext()) :
                             Type::getInt64Ty(V->getContext())))
-      return findValue(CI->getOperand(0), OffsetOk);
+      return findValueImpl(CI->getOperand(0), OffsetOk, Visited);
   } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
     if (Value *W = PN->hasConstantValue(DT))
-      return findValue(W, OffsetOk);
+      return findValueImpl(W, OffsetOk, Visited);
   } else if (ExtractValueInst *Ex = dyn_cast<ExtractValueInst>(V)) {
     if (Value *W = FindInsertedValue(Ex->getAggregateOperand(),
                                      Ex->idx_begin(),
                                      Ex->idx_end()))
       if (W != V)
-        return findValue(W, OffsetOk);
+        return findValueImpl(W, OffsetOk, Visited);
   }
 
   // As a last resort, try SimplifyInstruction or constant folding.
   if (Instruction *Inst = dyn_cast<Instruction>(V)) {
     if (Value *W = SimplifyInstruction(Inst, TD))
       if (W != Inst)
-        return findValue(W, OffsetOk);
+        return findValueImpl(W, OffsetOk, Visited);
   } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (Value *W = ConstantFoldConstantExpression(CE, TD))
       if (W != V)
-        return findValue(W, OffsetOk);
+        return findValueImpl(W, OffsetOk, Visited);
   }
 
   return V;

Modified: llvm/trunk/test/Other/lint.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Other/lint.ll?rev=104957&r1=104956&r2=104957&view=diff
==============================================================================
--- llvm/trunk/test/Other/lint.ll (original)
+++ llvm/trunk/test/Other/lint.ll Fri May 28 11:45:33 2010
@@ -122,3 +122,14 @@
   %t7 = inttoptr i64 %t6 to i32*
   ret i32* %t7
 }
+
+; CHECK: Undefined behavior: Undef pointer dereference
+define i32* @self_reference() {
+entry:
+  unreachable
+exit:
+  %t3 = phi i32* [ %t4, %exit ]
+  %t4 = bitcast i32* %t3 to i32*
+  %x = volatile load i32* %t3
+  br label %exit
+}