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[SCEV] Limit recursion depth of constant evolving.

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- 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
This commit is contained in:
Michael Liao 2017-01-13 18:28:30 +00:00
parent 68dd981647
commit 8a37b92c9a
1 changed files with 10 additions and 3 deletions
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13
lib/Analysis/ScalarEvolution.cpp
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@ -132,6 +132,10 @@ static cl::opt<unsigned>
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 @@ static bool canConstantEvolve(Instruction *I, const Loop *L) {
/// 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 @@ getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
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 @@ static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
// 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