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ScalarEvolution: Do not keep temporary PHI values in ValueExprMap

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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
This commit is contained in:
Tobias Grosser 2016-02-21 17:42:10 +00:00
parent ff9ee24191
commit e896bbb2c0
2 changed files with 31 additions and 0 deletions
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5
lib/Analysis/ScalarEvolution.cpp
View File

@ -3897,6 +3897,11 @@ const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
}
}
// Remove the temporary PHI node SCEV that has been inserted while intending
// to create an AddRecExpr for this PHI node. We can not keep this temporary
// as it will prevent later (possibly simpler) SCEV expressions to be added
// to the ValueExprMap.
ValueExprMap.erase(PN);
return nullptr;
}

26
unittests/Analysis/ScalarEvolutionTest.cpp
View File

@ -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