ScalarEvolution: Do not keep temporary PHI values in ValueExprMap

Before this patch simplified SCEV expressions for PHI nodes were only returned
the very first time getSCEV() was called, but later calls to getSCEV always
returned the non-simplified value, which had "temporarily" been stored in the
ValueExprMap, but was never removed and consequently blocked the caching of the
simplified PHI expression.

llvm-svn: 261485

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/unittests/Analysis/ScalarEvolutionTest.cpp b/llvm/unittests/Analysis/ScalarEvolutionTest.cpp
index 938dafe6038..4089e5dce56 100644
--- a/llvm/unittests/Analysis/ScalarEvolutionTest.cpp
+++ b/llvm/unittests/Analysis/ScalarEvolutionTest.cpp
@@ -237,5 +237,31 @@ TEST_F(ScalarEvolutionsTest, SCEVMultiplyAddRecs) {
   EXPECT_EQ(Product->getOperand(8), SE.getAddExpr(Sum));
 }
 
+TEST_F(ScalarEvolutionsTest, SimplifiedPHI) {
+  FunctionType *FTy = FunctionType::get(Type::getVoidTy(Context),
+                                              std::vector<Type *>(), false);
+  Function *F = cast<Function>(M.getOrInsertFunction("f", FTy));
+  BasicBlock *EntryBB = BasicBlock::Create(Context, "entry", F);
+  BasicBlock *LoopBB = BasicBlock::Create(Context, "loop", F);
+  BasicBlock *ExitBB = BasicBlock::Create(Context, "exit", F);
+  BranchInst::Create(LoopBB, EntryBB);
+  BranchInst::Create(LoopBB, ExitBB, UndefValue::get(Type::getInt1Ty(Context)),
+                     LoopBB);
+  ReturnInst::Create(Context, nullptr, ExitBB);
+  auto *Ty = Type::getInt32Ty(Context);
+  auto *PN = PHINode::Create(Ty, 2, "", &*LoopBB->begin());
+  PN->addIncoming(Constant::getNullValue(Ty), EntryBB);
+  PN->addIncoming(UndefValue::get(Ty), LoopBB);
+  ScalarEvolution SE = buildSE(*F);
+  auto *S1 = SE.getSCEV(PN);
+  auto *S2 = SE.getSCEV(PN);
+  assert(isa<SCEVConstant>(S1) && "Expected a SCEV Constant");
+
+  // At some point, only the first call to getSCEV returned the simplified
+  // SCEVConstant and later calls just returned a SCEVUnknown referencing the
+  // PHI node.
+  assert(S1 == S2 && "Expected identical SCEV values");
+}
+
 }  // end anonymous namespace
 }  // end namespace llvm