Fix reassociate to postpone certain instruction deletions until
after it has finished all of its reassociations, because its
habit of unlinking operands and holding them in a datastructure
while working means that it's not easy to determine when an
instruction is really dead until after all its regular work is
done. rdar://9096268.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127424 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index e093b52..6a0fb3f 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -22,6 +22,7 @@
#define DEBUG_TYPE "reassociate"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
@@ -74,6 +75,7 @@
class Reassociate : public FunctionPass {
DenseMap<BasicBlock*, unsigned> RankMap;
DenseMap<AssertingVH<>, unsigned> ValueRankMap;
+ SmallVector<WeakVH, 8> DeadInsts;
bool MadeChange;
public:
static char ID; // Pass identification, replacement for typeid
@@ -113,13 +115,13 @@
void Reassociate::RemoveDeadBinaryOp(Value *V) {
Instruction *Op = dyn_cast<Instruction>(V);
- if (!Op || !isa<BinaryOperator>(Op) || !Op->use_empty())
+ if (!Op || !isa<BinaryOperator>(Op))
return;
Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
ValueRankMap.erase(Op);
- Op->eraseFromParent();
+ DeadInsts.push_back(Op);
RemoveDeadBinaryOp(LHS);
RemoveDeadBinaryOp(RHS);
}
@@ -603,7 +605,7 @@
// remaining operand.
if (Factors.size() == 1) {
ValueRankMap.erase(BO);
- BO->eraseFromParent();
+ DeadInsts.push_back(BO);
V = Factors[0].Op;
} else {
RewriteExprTree(BO, Factors);
@@ -1093,6 +1095,12 @@
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
ReassociateBB(FI);
+ // Now that we're done, delete any instructions which are no longer used.
+ while (!DeadInsts.empty())
+ if (Instruction *Inst =
+ cast_or_null<Instruction>((Value *)DeadInsts.pop_back_val()))
+ RecursivelyDeleteTriviallyDeadInstructions(Inst);
+
// We are done with the rank map.
RankMap.clear();
ValueRankMap.clear();