[X86] isTargetShuffleEquivalent - add BUILD_VECTOR matching

Add similar functionality to isShuffleEquivalent - if the mask elements don't match, try matching the BUILD_VECTOR scalars instead.

As target shuffles need to handle SM_Sentinel values, this can get a bit tricky, so commit just adds actual mask element index handling - full SM_SentinelZero support will be added when the need arises.

Also, enables support in matchVectorShuffleWithPACK

llvm-svn: 369212

1 files changed, 21 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 6c739d8aad6..ac616ffa8ba 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -10078,7 +10078,9 @@ static bool isShuffleEquivalent(SDValue V1, SDValue V2, ArrayRef<int> Mask,
 /// SM_SentinelZero is accepted as a valid negative index but must match in
 /// both.
 static bool isTargetShuffleEquivalent(ArrayRef<int> Mask,
-                                      ArrayRef<int> ExpectedMask) {
+                                      ArrayRef<int> ExpectedMask,
+                                      SDValue V1 = SDValue(),
+                                      SDValue V2 = SDValue()) {
   int Size = Mask.size();
   if (Size != (int)ExpectedMask.size())
     return false;
@@ -10089,9 +10091,25 @@ static bool isTargetShuffleEquivalent(ArrayRef<int> Mask,
   if (!isUndefOrZeroOrInRange(Mask, 0, 2 * Size))
     return false;
 
+  // If the values are build vectors, we can look through them to find
+  // equivalent inputs that make the shuffles equivalent.
+  auto *BV1 = dyn_cast_or_null<BuildVectorSDNode>(V1);
+  auto *BV2 = dyn_cast_or_null<BuildVectorSDNode>(V2);
+  BV1 = ((BV1 && BV1->getNumOperands() != Size) ? nullptr : BV1);
+  BV2 = ((BV2 && BV2->getNumOperands() != Size) ? nullptr : BV2);
+
   for (int i = 0; i < Size; ++i) {
     if (Mask[i] == SM_SentinelUndef || Mask[i] == ExpectedMask[i])
       continue;
+    if (0 <= Mask[i] && 0 <= ExpectedMask[i]) {
+      auto *MaskBV = Mask[i] < Size ? BV1 : BV2;
+      auto *ExpectedBV = ExpectedMask[i] < Size ? BV1 : BV2;
+      if (MaskBV && ExpectedBV &&
+          MaskBV->getOperand(Mask[i] % Size) ==
+              ExpectedBV->getOperand(ExpectedMask[i] % Size))
+        continue;
+    }
+    // TODO - handle SM_Sentinel equivalences.
     return false;
   }
   return true;
@@ -10653,14 +10671,14 @@ static bool matchVectorShuffleWithPACK(MVT VT, MVT &SrcVT, SDValue &V1,
   // Try binary shuffle.
   SmallVector<int, 32> BinaryMask;
   createPackShuffleMask(VT, BinaryMask, false);
-  if (isTargetShuffleEquivalent(TargetMask, BinaryMask))
+  if (isTargetShuffleEquivalent(TargetMask, BinaryMask, V1, V2))
     if (MatchPACK(V1, V2))
       return true;
 
   // Try unary shuffle.
   SmallVector<int, 32> UnaryMask;
   createPackShuffleMask(VT, UnaryMask, true);
-  if (isTargetShuffleEquivalent(TargetMask, UnaryMask))
+  if (isTargetShuffleEquivalent(TargetMask, UnaryMask, V1))
     if (MatchPACK(V1, V1))
       return true;