From 878c144f8a32336daa2c0124017ec707924cfcc0 Mon Sep 17 00:00:00 2001 From: Matt Wala Date: Thu, 23 Jul 2015 20:53:46 +0000 Subject: [Scalarizer] Fix potential for stale data in Scattered across invocations Summary: Scalarizer has two data structures that hold information about changes to the function, Gathered and Scattered. These are cleared in finish() at the end of runOnFunction() if finish() detects any changes to the function. However, finish() was checking for changes by only checking if Gathered was non-empty. The function visitStore() only modifies Scattered without touching Gathered. As a result, Scattered could have ended up having stale data if Scalarizer only scalarized store instructions. Since the data in Scattered is used during the execution of the pass, this introduced dangling pointer errors. The fix is to check whether both Scattered and Gathered are empty before deciding what to do in finish(). This also fixes a problem where the Function can be modified although the pass returns false. Reviewers: rnk Subscribers: rnk, srhines, llvm-commits Differential Revision: http://reviews.llvm.org/D10459 llvm-svn: 243040 --- llvm/lib/Transforms/Scalar/Scalarizer.cpp | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'llvm/lib') diff --git a/llvm/lib/Transforms/Scalar/Scalarizer.cpp b/llvm/lib/Transforms/Scalar/Scalarizer.cpp index d55dc6a20a0..3b8307c4316 100644 --- a/llvm/lib/Transforms/Scalar/Scalarizer.cpp +++ b/llvm/lib/Transforms/Scalar/Scalarizer.cpp @@ -247,6 +247,7 @@ bool Scalarizer::doInitialization(Module &M) { } bool Scalarizer::runOnFunction(Function &F) { + assert(Gathered.empty() && Scattered.empty()); for (Function::iterator BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) { BasicBlock *BB = BBI; for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) { @@ -636,7 +637,9 @@ bool Scalarizer::visitStoreInst(StoreInst &SI) { // Delete the instructions that we scalarized. If a full vector result // is still needed, recreate it using InsertElements. bool Scalarizer::finish() { - if (Gathered.empty()) + // The presence of data in Gathered or Scattered indicates changes + // made to the Function. + if (Gathered.empty() && Scattered.empty()) return false; for (GatherList::iterator GMI = Gathered.begin(), GME = Gathered.end(); GMI != GME; ++GMI) { -- cgit v1.2.3