[CodeGen][ShrinkWrap] Clarify StackAddressUsedBlockInfo meaning (#80679)
diff --git a/llvm/lib/CodeGen/ShrinkWrap.cpp b/llvm/lib/CodeGen/ShrinkWrap.cpp
index ab57d08..a4b2299 100644
--- a/llvm/lib/CodeGen/ShrinkWrap.cpp
+++ b/llvm/lib/CodeGen/ShrinkWrap.cpp
@@ -161,9 +161,11 @@
/// Current MachineFunction.
MachineFunction *MachineFunc = nullptr;
- /// Is `true` for block numbers where we can guarantee no stack access
- /// or computation of stack-relative addresses on any CFG path including
- /// the block itself.
+ /// Is `true` for the block numbers where we assume possible stack accesses
+ /// or computation of stack-relative addresses on any CFG path including the
+ /// block itself. Is `false` for basic blocks where we can guarantee the
+ /// opposite. False positives won't lead to incorrect analysis results,
+ /// therefore this approach is fair.
BitVector StackAddressUsedBlockInfo;
/// Check if \p MI uses or defines a callee-saved register or
@@ -948,6 +950,9 @@
bool Changed = false;
+ // Initially, conservatively assume that stack addresses can be used in each
+ // basic block and change the state only for those basic blocks for which we
+ // were able to prove the opposite.
StackAddressUsedBlockInfo.resize(MF.getNumBlockIDs(), true);
bool HasCandidate = performShrinkWrapping(RPOT, RS.get());
StackAddressUsedBlockInfo.clear();
