[DAG] Fold FrameIndex offset into BaseIndexOffset analysis. NFCI.

Relanding after restricting equalBaseIndex to not erroneuosly consider
a FrameIndices stemming from alloca from being comparable as its
offset is set post-selectionDAG.

Pull FrameIndex comparision reasoning from DAGCombiner::isAlias to
general BaseIndexOffset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306688 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/SelectionDAGAddressAnalysis.h

@@ -57,7 +57,7 @@ public:
                       int64_t &Off);
 
   /// Parses tree in Ptr for base, index, offset addresses.
-  static BaseIndexOffset match(SDValue Ptr);
+  static BaseIndexOffset match(SDValue Ptr, const SelectionDAG &DAG);
 };
 } // namespace llvm
 

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4915,7 +4915,7 @@ SDValue DAGCombiner::MatchLoadCombine(SDNode *N) {
       return SDValue();
 
     // Loads must share the same base address
-    BaseIndexOffset Ptr = BaseIndexOffset::match(L->getBasePtr());
+    BaseIndexOffset Ptr = BaseIndexOffset::match(L->getBasePtr(), DAG);
     int64_t ByteOffsetFromBase = 0;
     if (!Base)
       Base = Ptr;
@@ -12442,7 +12442,7 @@ void DAGCombiner::getStoreMergeCandidates(
     StoreSDNode *St, SmallVectorImpl<MemOpLink> &StoreNodes) {
   // This holds the base pointer, index, and the offset in bytes from the base
   // pointer.
-  BaseIndexOffset BasePtr = BaseIndexOffset::match(St->getBasePtr());
+  BaseIndexOffset BasePtr = BaseIndexOffset::match(St->getBasePtr(), DAG);
   EVT MemVT = St->getMemoryVT();
 
   // We must have a base and an offset.
@@ -12462,8 +12462,8 @@ void DAGCombiner::getStoreMergeCandidates(
   BaseIndexOffset LBasePtr;
   // Match on loadbaseptr if relevant.
   if (IsLoadSrc)
-    LBasePtr =
-        BaseIndexOffset::match(cast<LoadSDNode>(St->getValue())->getBasePtr());
+    LBasePtr = BaseIndexOffset::match(
+        cast<LoadSDNode>(St->getValue())->getBasePtr(), DAG);
 
   auto CandidateMatch = [&](StoreSDNode *Other, BaseIndexOffset &Ptr,
                             int64_t &Offset) -> bool {
@@ -12477,7 +12477,7 @@ void DAGCombiner::getStoreMergeCandidates(
     if (IsLoadSrc) {
       // The Load's Base Ptr must also match
       if (LoadSDNode *OtherLd = dyn_cast<LoadSDNode>(Other->getValue())) {
-        auto LPtr = BaseIndexOffset::match(OtherLd->getBasePtr());
+        auto LPtr = BaseIndexOffset::match(OtherLd->getBasePtr(), DAG);
         if (!(LBasePtr.equalBaseIndex(LPtr, DAG)))
           return false;
       } else
@@ -12491,7 +12491,7 @@ void DAGCombiner::getStoreMergeCandidates(
       if (!(Other->getValue().getOpcode() == ISD::EXTRACT_VECTOR_ELT ||
             Other->getValue().getOpcode() == ISD::EXTRACT_SUBVECTOR))
         return false;
-    Ptr = BaseIndexOffset::match(Other->getBasePtr());
+    Ptr = BaseIndexOffset::match(Other->getBasePtr(), DAG);
     return (BasePtr.equalBaseIndex(Ptr, DAG, Offset));
   };
   // We looking for a root node which is an ancestor to all mergable
@@ -12834,7 +12834,7 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode *St) {
       if (Ld->getMemoryVT() != MemVT)
         break;
 
-      BaseIndexOffset LdPtr = BaseIndexOffset::match(Ld->getBasePtr());
+      BaseIndexOffset LdPtr = BaseIndexOffset::match(Ld->getBasePtr(), DAG);
       // If this is not the first ptr that we check.
       int64_t LdOffset = 0;
       if (LdBasePtr.getBase().getNode()) {
@@ -16602,8 +16602,8 @@ bool DAGCombiner::isAlias(LSBaseSDNode *Op0, LSBaseSDNode *Op1) const {
   unsigned NumBytes1 = Op1->getMemoryVT().getSizeInBits() >> 3;
 
   // Check for BaseIndexOffset matching.
-  BaseIndexOffset BasePtr0 = BaseIndexOffset::match(Op0->getBasePtr());
-  BaseIndexOffset BasePtr1 = BaseIndexOffset::match(Op1->getBasePtr());
+  BaseIndexOffset BasePtr0 = BaseIndexOffset::match(Op0->getBasePtr(), DAG);
+  BaseIndexOffset BasePtr1 = BaseIndexOffset::match(Op1->getBasePtr(), DAG);
   int64_t PtrDiff;
   if (BasePtr0.equalBaseIndex(BasePtr1, DAG, PtrDiff))
     return !((NumBytes0 <= PtrDiff) || (PtrDiff + NumBytes1 <= 0));
@@ -16813,7 +16813,7 @@ SDValue DAGCombiner::FindBetterChain(SDNode *N, SDValue OldChain) {
 bool DAGCombiner::findBetterNeighborChains(StoreSDNode *St) {
   // This holds the base pointer, index, and the offset in bytes from the base
   // pointer.
-  BaseIndexOffset BasePtr = BaseIndexOffset::match(St->getBasePtr());
+  BaseIndexOffset BasePtr = BaseIndexOffset::match(St->getBasePtr(), DAG);
 
   // We must have a base and an offset.
   if (!BasePtr.getBase().getNode())
@@ -16839,7 +16839,7 @@ bool DAGCombiner::findBetterNeighborChains(StoreSDNode *St) {
       break;
 
     // Find the base pointer and offset for this memory node.
-    BaseIndexOffset Ptr = BaseIndexOffset::match(Index->getBasePtr());
+    BaseIndexOffset Ptr = BaseIndexOffset::match(Index->getBasePtr(), DAG);
 
     // Check that the base pointer is the same as the original one.
     if (!BasePtr.equalBaseIndex(Ptr, DAG))

lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp

@@ -11,6 +11,7 @@
 
 #include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
 #include "llvm/CodeGen/ISDOpcodes.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/SelectionDAGNodes.h"
 
@@ -18,28 +19,41 @@ namespace llvm {
 
 bool BaseIndexOffset::equalBaseIndex(BaseIndexOffset &Other,
                                      const SelectionDAG &DAG, int64_t &Off) {
-  // Obvious equivalent
+  // Initial Offset difference.
   Off = Other.Offset - Offset;
-  if (Other.Base == Base && Other.Index == Index &&
-      Other.IsIndexSignExt == IsIndexSignExt)
-    return true;
 
-  // Match GlobalAddresses
-  if (Index == Other.Index)
-    if (GlobalAddressSDNode *A = dyn_cast<GlobalAddressSDNode>(Base))
-      if (GlobalAddressSDNode *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
+  if ((Other.Index == Index) && (Other.IsIndexSignExt == IsIndexSignExt)) {
+    // Trivial match.
+    if (Other.Base == Base)
+      return true;
+
+    // Match GlobalAddresses
+    if (auto *A = dyn_cast<GlobalAddressSDNode>(Base))
+      if (auto *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
         if (A->getGlobal() == B->getGlobal()) {
           Off += B->getOffset() - A->getOffset();
           return true;
         }
 
-  // TODO: we should be able to add FrameIndex analysis improvements here.
+    const MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
 
+    // Match non-equal FrameIndexes - a FrameIndex stemming from an
+    // alloca will not have it's ObjectOffset set until post-DAG and
+    // as such we must assume the two framesIndices are incomparable.
+    if (auto *A = dyn_cast<FrameIndexSDNode>(Base))
+      if (auto *B = dyn_cast<FrameIndexSDNode>(Other.Base))
+        if (!MFI.getObjectAllocation(A->getIndex()) &&
+            !MFI.getObjectAllocation(B->getIndex())) {
+          Off += MFI.getObjectOffset(B->getIndex()) -
+                 MFI.getObjectOffset(A->getIndex());
+          return true;
+        }
+  }
   return false;
 }
 
 /// Parses tree in Ptr for base, index, offset addresses.
-BaseIndexOffset BaseIndexOffset::match(SDValue Ptr) {
+BaseIndexOffset BaseIndexOffset::match(SDValue Ptr, const SelectionDAG &DAG) {
   // (((B + I*M) + c)) + c ...
   SDValue Base = Ptr;
   SDValue Index = SDValue();