================
@@ -110,15 +117,32 @@ bool UseAfterMoveFinder::find(Stmt *CodeBlock, const Expr
*MovingCall,
BlockMap = std::make_unique<StmtToBlockMap>(TheCFG.get(), Context);
Visited.clear();
- const CFGBlock *Block = BlockMap->blockContainingStmt(MovingCall);
- if (!Block) {
+ const CFGBlock *MoveBlock = BlockMap->blockContainingStmt(MovingCall);
+ if (!MoveBlock) {
// This can happen if MovingCall is in a constructor initializer, which is
// not included in the CFG because the CFG is built only from the function
// body.
- Block = &TheCFG->getEntry();
+ MoveBlock = &TheCFG->getEntry();
}
- return findInternal(Block, MovingCall, MovedVariable, TheUseAfterMove);
+ bool Found = findInternal(MoveBlock, MovingCall, MovedVariable->getDecl(),
+ TheUseAfterMove);
+
+ if (Found) {
+ if (const CFGBlock *UseBlock =
+ BlockMap->blockContainingStmt(TheUseAfterMove->DeclRef)) {
+ // Does the use happen in a later loop iteration than the move?
+ // - If they are in the same CFG block, we know the use happened in a
+ // later iteration if we visited that block a second time.
+ // - Otherwise, we know the use happened in a later iteration if the
+ // move is reachable from the use.
+ auto CFA =
std::make_unique<CFGReverseBlockReachabilityAnalysis>(*TheCFG);
+ TheUseAfterMove->UseHappensInLaterLoopIteration =
+ UseBlock == MoveBlock ? Visited.contains(UseBlock)
+ : CFA->isReachable(UseBlock, MoveBlock);
----------------
tchaikov wrote:
`CFGReverseBlockReachabilityAnalysis` comes with two member variables of
`llvm::BitVector` and `llvm::DenseMap<>`, which could be potentially too large
to put on the stack, i thought. that's why i allocated it on heap. but if you
believe it's safe to do so. will allocate it on stack.
https://github.com/llvm/llvm-project/pull/93623
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