Re-land the refactoring part of r354244 "[DAGCombiner] Eliminate dead stores to stack."
This is an NFC.
llvm-svn: 354476
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
index 5666c12..c21ecfc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
@@ -79,6 +79,81 @@
return false;
}
+bool BaseIndexOffset::computeAliasing(const BaseIndexOffset &BasePtr0,
+ const int64_t NumBytes0,
+ const BaseIndexOffset &BasePtr1,
+ const int64_t NumBytes1,
+ const SelectionDAG &DAG, bool &IsAlias) {
+ if (!(BasePtr0.getBase().getNode() && BasePtr1.getBase().getNode()))
+ return false;
+ int64_t PtrDiff;
+ if (BasePtr0.equalBaseIndex(BasePtr1, DAG, PtrDiff)) {
+ // BasePtr1 is PtrDiff away from BasePtr0. They alias if none of the
+ // following situations arise:
+ IsAlias = !(
+ // [----BasePtr0----]
+ // [---BasePtr1--]
+ // ========PtrDiff========>
+ (NumBytes0 <= PtrDiff) ||
+ // [----BasePtr0----]
+ // [---BasePtr1--]
+ // =====(-PtrDiff)====>
+ (PtrDiff + NumBytes1 <= 0)); // i.e. NumBytes1 < -PtrDiff.
+ return true;
+ }
+ // If both BasePtr0 and BasePtr1 are FrameIndexes, we will not be
+ // able to calculate their relative offset if at least one arises
+ // from an alloca. However, these allocas cannot overlap and we
+ // can infer there is no alias.
+ if (auto *A = dyn_cast<FrameIndexSDNode>(BasePtr0.getBase()))
+ if (auto *B = dyn_cast<FrameIndexSDNode>(BasePtr1.getBase())) {
+ MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
+ // If the base are the same frame index but the we couldn't find a
+ // constant offset, (indices are different) be conservative.
+ if (A != B && (!MFI.isFixedObjectIndex(A->getIndex()) ||
+ !MFI.isFixedObjectIndex(B->getIndex()))) {
+ IsAlias = false;
+ return true;
+ }
+ }
+
+ bool IsFI0 = isa<FrameIndexSDNode>(BasePtr0.getBase());
+ bool IsFI1 = isa<FrameIndexSDNode>(BasePtr1.getBase());
+ bool IsGV0 = isa<GlobalAddressSDNode>(BasePtr0.getBase());
+ bool IsGV1 = isa<GlobalAddressSDNode>(BasePtr1.getBase());
+ bool IsCV0 = isa<ConstantPoolSDNode>(BasePtr0.getBase());
+ bool IsCV1 = isa<ConstantPoolSDNode>(BasePtr1.getBase());
+
+ // If of mismatched base types or checkable indices we can check
+ // they do not alias.
+ if ((BasePtr0.getIndex() == BasePtr1.getIndex() || (IsFI0 != IsFI1) ||
+ (IsGV0 != IsGV1) || (IsCV0 != IsCV1)) &&
+ (IsFI0 || IsGV0 || IsCV0) && (IsFI1 || IsGV1 || IsCV1)) {
+ IsAlias = false;
+ return true;
+ }
+ return false; // Cannot determine whether the pointers alias.
+}
+
+bool BaseIndexOffset::contains(int64_t Size, const BaseIndexOffset &Other,
+ int64_t OtherSize,
+ const SelectionDAG &DAG) const {
+ int64_t Offset;
+ if (!equalBaseIndex(Other, DAG, Offset))
+ return false;
+ if (Offset >= 0) {
+ // Other is after *this:
+ // [-------*this---------]
+ // [---Other--]
+ // ==Offset==>
+ return Offset + OtherSize <= Size;
+ }
+ // Other starts strictly before *this, it cannot be fully contained.
+ // [-------*this---------]
+ // [--Other--]
+ return false;
+}
+
/// Parses tree in Ptr for base, index, offset addresses.
BaseIndexOffset BaseIndexOffset::match(const LSBaseSDNode *N,
const SelectionDAG &DAG) {