[llvm] r218980 - [x86] Refactor the element insertion logic in the new vector shuffle

[Chandler Carruth]

Author: chandlerc
Date: Fri Oct  3 07:01:55 2014
New Revision: 218980

URL: http://llvm.org/viewvc/llvm-project?rev=218980&view=rev
Log:
[x86] Refactor the element insertion logic in the new vector shuffle
lowering to handle the potential mirroring of 2-element vectors (because
we can't reliably sort them one way) in the caller rather than in the
insertion logic.

This will simplify things considerably as more ways to fail to match the
insertion are added because now we have a nice try and retry point.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=218980&r1=218979&r2=218980&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Fri Oct  3 07:01:55 2014
@@ -7783,23 +7783,9 @@ static SDValue lowerVectorShuffleAsEleme
   int V2Index = std::find_if(Mask.begin(), Mask.end(),
                              [&Mask](int M) { return M >= (int)Mask.size(); }) -
                 Mask.begin();
-  if (Mask.size() == 2) {
-    if (!Zeroable[V2Index ^ 1]) {
-      // For 2-wide masks we may be able to just invert the inputs. We use an xor
-      // with 2 to flip from {2,3} to {0,1} and vice versa.
-      int InverseMask[2] = {Mask[0] < 0 ? -1 : (Mask[0] ^ 2),
-                            Mask[1] < 0 ? -1 : (Mask[1] ^ 2)};
-      if (Zeroable[V2Index])
-        return lowerVectorShuffleAsElementInsertion(VT, DL, V2, V1, InverseMask,
-                                                    Subtarget, DAG);
-      else
-        return SDValue();
-    }
-  } else {
-    for (int i = 0, Size = Mask.size(); i < Size; ++i)
-      if (i != V2Index && !Zeroable[i])
-        return SDValue(); // Not inserting into a zero vector.
-  }
+  for (int i = 0, Size = Mask.size(); i < Size; ++i)
+    if (i != V2Index && !Zeroable[i])
+      return SDValue(); // Not inserting into a zero vector.
 
   MVT ExtVT = VT;
   MVT EltVT = VT.getVectorElementType();
@@ -7940,10 +7926,18 @@ static SDValue lowerV2F64VectorShuffle(S
     return DAG.getNode(X86ISD::UNPCKH, DL, MVT::v2f64, V1, V2);
 
   // If we have a single input, insert that into V1 if we can do so cheaply.
-  if ((Mask[0] >= 2) + (Mask[1] >= 2) == 1)
+  if ((Mask[0] >= 2) + (Mask[1] >= 2) == 1) {
     if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
             MVT::v2f64, DL, V1, V2, Mask, Subtarget, DAG))
       return Insertion;
+    // Try inverting the insertion since for v2 masks it is easy to do and we
+    // can't reliably sort the mask one way or the other.
+    int InverseMask[2] = {Mask[0] < 0 ? -1 : (Mask[0] ^ 2),
+                          Mask[1] < 0 ? -1 : (Mask[1] ^ 2)};
+    if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
+            MVT::v2f64, DL, V2, V1, InverseMask, Subtarget, DAG))
+      return Insertion;
+  }
 
   // Try to use one of the special instruction patterns to handle two common
   // blend patterns if a zero-blend above didn't work.
@@ -8004,10 +7998,18 @@ static SDValue lowerV2I64VectorShuffle(S
 
   // If we have a single input from V2 insert that into V1 if we can do so
   // cheaply.
-  if ((Mask[0] >= 2) + (Mask[1] >= 2) == 1)
+  if ((Mask[0] >= 2) + (Mask[1] >= 2) == 1) {
     if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
             MVT::v2i64, DL, V1, V2, Mask, Subtarget, DAG))
       return Insertion;
+    // Try inverting the insertion since for v2 masks it is easy to do and we
+    // can't reliably sort the mask one way or the other.
+    int InverseMask[2] = {Mask[0] < 0 ? -1 : (Mask[0] ^ 2),
+                          Mask[1] < 0 ? -1 : (Mask[1] ^ 2)};
+    if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
+            MVT::v2i64, DL, V2, V1, InverseMask, Subtarget, DAG))
+      return Insertion;
+  }
 
   // Use dedicated unpack instructions for masks that match their pattern.
   if (isShuffleEquivalent(Mask, 0, 2))