[SCEV] Limit recursion depth of constant evolving.
- For a loop body with VERY complicated exit condition evaluation, constant
evolving may run out of stack on platforms such as Windows. Need to limit the
recursion depth.
Differential Revision: https://reviews.llvm.org/D28629
llvm-svn: 291927
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index b3905cc..8164852 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -132,6 +132,10 @@
cl::desc("Maximum depth of recursive compare complexity"),
cl::init(32));
+static cl::opt<unsigned> MaxConstantEvolvingDepth(
+ "scalar-evolution-max-constant-evolving-depth", cl::Hidden,
+ cl::desc("Maximum depth of recursive constant evolving"), cl::init(32));
+
//===----------------------------------------------------------------------===//
// SCEV class definitions
//===----------------------------------------------------------------------===//
@@ -6403,7 +6407,10 @@
/// recursing through each instruction operand until reaching a loop header phi.
static PHINode *
getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
- DenseMap<Instruction *, PHINode *> &PHIMap) {
+ DenseMap<Instruction *, PHINode *> &PHIMap,
+ unsigned Depth) {
+ if (Depth > MaxConstantEvolvingDepth)
+ return nullptr;
// Otherwise, we can evaluate this instruction if all of its operands are
// constant or derived from a PHI node themselves.
@@ -6423,7 +6430,7 @@
if (!P) {
// Recurse and memoize the results, whether a phi is found or not.
// This recursive call invalidates pointers into PHIMap.
- P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
+ P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap, Depth + 1);
PHIMap[OpInst] = P;
}
if (!P)
@@ -6450,7 +6457,7 @@
// Record non-constant instructions contained by the loop.
DenseMap<Instruction *, PHINode *> PHIMap;
- return getConstantEvolvingPHIOperands(I, L, PHIMap);
+ return getConstantEvolvingPHIOperands(I, L, PHIMap, 0);
}
/// EvaluateExpression - Given an expression that passes the