[llvm-commits] [llvm] r155722 - /llvm/trunk/lib/Transforms/Scalar/GVN.cpp

[Mon P Wang]

Author: wangmp
Date: Fri Apr 27 13:09:28 2012
New Revision: 155722

URL: http://llvm.org/viewvc/llvm-project?rev=155722&view=rev
Log:
Add an early bailout to IsValueFullyAvailableInBlock from deeply nested blocks.
The limit is set to an arbitrary 1000 recursion depth to avoid stack overflow
issues. <rdar://problem/11286839>.


Modified:
    llvm/trunk/lib/Transforms/Scalar/GVN.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=155722&r1=155721&r2=155722&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Fri Apr 27 13:09:28 2012
@@ -59,6 +59,11 @@
                                cl::init(true), cl::Hidden);
 static cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true));
 
+// Maximum allowed recursion depth.
+static cl::opt<int>
+MaxRecurseDepth("max-recurse-depth", cl::Hidden, cl::init(1000), cl::ZeroOrMore,
+                cl::desc("Max recurse depth (default = 1000)"));
+
 //===----------------------------------------------------------------------===//
 //                         ValueTable Class
 //===----------------------------------------------------------------------===//
@@ -647,7 +652,11 @@
 ///   3) we are speculating for this block and have used that to speculate for
 ///      other blocks.
 static bool IsValueFullyAvailableInBlock(BasicBlock *BB,
-                            DenseMap<BasicBlock*, char> &FullyAvailableBlocks) {
+                            DenseMap<BasicBlock*, char> &FullyAvailableBlocks,
+                            uint32_t RecurseDepth) {
+  if (RecurseDepth > MaxRecurseDepth)
+    return false;
+
   // Optimistically assume that the block is fully available and check to see
   // if we already know about this block in one lookup.
   std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
@@ -673,7 +682,7 @@
     // If the value isn't fully available in one of our predecessors, then it
     // isn't fully available in this block either.  Undo our previous
     // optimistic assumption and bail out.
-    if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks))
+    if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks,RecurseDepth+1))
       goto SpeculationFailure;
 
   return true;
@@ -1570,7 +1579,7 @@
   for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
        PI != E; ++PI) {
     BasicBlock *Pred = *PI;
-    if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks)) {
+    if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks, 0)) {
       continue;
     }
     PredLoads[Pred] = 0;