Fix PR9039, a use-after-free in reassociate. The issue was that the

operand being factorized (and erased) could occur several times in Ops,
resulting in freed memory being used when the next occurrence in Ops was
analyzed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124287 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index 46b7f95258111be982a2cacd291176220afd652d..396b329980772ecf1ddce987d50897285f7ff4b4 100644 (file)
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -811,16 +811,23 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
     // RemoveFactorFromExpression on successive values to behave differently.
     Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
     SmallVector<Value*, 4> NewMulOps;
-    for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+    for (unsigned i = 0; i != Ops.size(); ++i) {
       // Only try to remove factors from expressions we're allowed to.
       BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
       if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
         continue;
       
       if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
-        NewMulOps.push_back(V);
-        Ops.erase(Ops.begin()+i);
-        --i; --e;
+        // The factorized operand may occur several times.  Convert them all in
+        // one fell swoop.
+        for (unsigned j = Ops.size(); j != i;) {
+          --j;
+          if (Ops[j].Op == Ops[i].Op) {
+            NewMulOps.push_back(V);
+            Ops.erase(Ops.begin()+j);
+          }
+        }
+        --i;
       }
     }
     

diff --git a/test/Transforms/Reassociate/2011-01-26-UseAfterFree.ll b/test/Transforms/Reassociate/2011-01-26-UseAfterFree.ll
new file mode 100644 (file)
index 0000000..e6c76b3
--- /dev/null
+++ b/test/Transforms/Reassociate/2011-01-26-UseAfterFree.ll
@@ -0,0 +1,35 @@
+; RUN: opt < %s -reassociate
+; PR9039
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
+target triple = "i386-gnu-linux"
+
+%ada__tags__T15s = type void ()
+
+define void @exp_averages_intraday__deviation() {
+entry:
+  %0 = load i32* undef, align 4
+  %1 = shl i32 %0, 2
+  %2 = add nsw i32 undef, %1
+  %3 = add nsw i32 %2, undef
+  %4 = mul nsw i32 %0, 12
+  %5 = add nsw i32 %3, %4
+  %6 = add nsw i32 %5, %4
+  %7 = add nsw i32 %6, undef
+  br i1 false, label %"4", label %"12"
+
+"4":                                              ; preds = %entry
+  br i1 undef, label %"5", label %"8"
+
+"5":                                              ; preds = %"4"
+  unreachable
+
+"8":                                              ; preds = %"4"
+  %8 = getelementptr inbounds i8* undef, i32 %6
+  br i1 undef, label %"13", label %"12"
+
+"12":                                             ; preds = %"8", %entry
+  ret void
+
+"13":                                             ; preds = %"8"
+  ret void
+}