widen shuffle mask as late as possible

Author: tangaac

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

@@ -544,6 +544,37 @@ SDValue LoongArchTargetLowering::lowerBITREVERSE(SDValue Op,
   }
 }
 
+// Widen element type to get a new mask value (if possible).
+// For example:
+//  shufflevector <4 x i32> %a, <4 x i32> %b,
+//                <4 x i32> <i32 6, i32 7, i32 2, i32 3>
+// is equivalent to:
+//  shufflevector <2 x i64> %a, <2 x i64> %b, <2 x i32> <i32 3, i32 1>
+// can be lowered to:
+//  VPACKOD_D vr0, vr0, vr1
+static SDValue widenShuffleMask(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
+                                SDValue V1, SDValue V2, SelectionDAG &DAG) {
+  unsigned EltBits = VT.getScalarSizeInBits();
+
+  if (EltBits > 32 || EltBits == 1)
+    return SDValue();
+
+  SmallVector<int, 8> NewMask;
+  if (widenShuffleMaskElts(Mask, NewMask)) {
+    MVT NewEltVT = VT.isFloatingPoint() ? MVT::getFloatingPointVT(EltBits * 2)
+                                        : MVT::getIntegerVT(EltBits * 2);
+    MVT NewVT = MVT::getVectorVT(NewEltVT, VT.getVectorNumElements() / 2);
+    if (DAG.getTargetLoweringInfo().isTypeLegal(NewVT)) {
+      SDValue NewV1 = DAG.getBitcast(NewVT, V1);
+      SDValue NewV2 = DAG.getBitcast(NewVT, V2);
+      return DAG.getBitcast(
+          VT, DAG.getVectorShuffle(NewVT, DL, NewV1, NewV2, NewMask));
+    }
+  }
+
+  return SDValue();
+}
+
 /// Attempts to match a shuffle mask against the VBSLL, VBSRL, VSLLI and VSRLI
 /// instruction.
 // The funciton matches elements from one of the input vector shuffled to the
@@ -1366,6 +1397,8 @@ static SDValue lower128BitShuffle(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
     return Result;
   if ((Result = lowerVECTOR_SHUFFLEAsByteRotate(DL, Mask, VT, V1, V2, DAG)))
     return Result;
+  if (SDValue NewShuffle = widenShuffleMask(DL, Mask, VT, V1, V2, DAG))
+    return NewShuffle;
   if ((Result = lowerVECTOR_SHUFFLE_VSHUF(DL, Mask, VT, V1, V2, DAG)))
     return Result;
   return SDValue();
@@ -1804,41 +1837,13 @@ static SDValue lower256BitShuffle(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
     return Result;
   if ((Result = lowerVECTOR_SHUFFLEAsByteRotate(DL, NewMask, VT, V1, V2, DAG)))
     return Result;
+  if (SDValue NewShuffle = widenShuffleMask(DL, NewMask, VT, V1, V2, DAG))
+    return NewShuffle;
   if ((Result = lowerVECTOR_SHUFFLE_XVSHUF(DL, NewMask, VT, V1, V2, DAG)))
     return Result;
 
   return SDValue();
 }
-// Widen element type to get a new mask value (if possible).
-// For example:
-//  shufflevector <4 x i32> %a, <4 x i32> %b,
-//                <4 x i32> <i32 6, i32 7, i32 2, i32 3>
-// is equivalent to:
-//  shufflevector <2 x i64> %a, <2 x i64> %b, <2 x i32> <i32 3, i32 1>
-// can be lowered to:
-//  VPACKOD_D vr0, vr0, vr1
-static SDValue widenShuffleMask(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
-                                SDValue V1, SDValue V2, SelectionDAG &DAG) {
-  unsigned EltBits = VT.getScalarSizeInBits();
-
-  if (EltBits > 32 || EltBits == 1)
-    return SDValue();
-
-  SmallVector<int, 8> NewMask;
-  if (widenShuffleMaskElts(Mask, NewMask)) {
-    MVT NewEltVT = VT.isFloatingPoint() ? MVT::getFloatingPointVT(EltBits * 2)
-                                        : MVT::getIntegerVT(EltBits * 2);
-    MVT NewVT = MVT::getVectorVT(NewEltVT, VT.getVectorNumElements() / 2);
-    if (DAG.getTargetLoweringInfo().isTypeLegal(NewVT)) {
-      SDValue NewV1 = DAG.getBitcast(NewVT, V1);
-      SDValue NewV2 = DAG.getBitcast(NewVT, V2);
-      return DAG.getBitcast(
-          VT, DAG.getVectorShuffle(NewVT, DL, NewV1, NewV2, NewMask));
-    }
-  }
-
-  return SDValue();
-}
 
 SDValue LoongArchTargetLowering::lowerVECTOR_SHUFFLE(SDValue Op,
                                                      SelectionDAG &DAG) const {
@@ -1873,9 +1878,6 @@ SDValue LoongArchTargetLowering::lowerVECTOR_SHUFFLE(SDValue Op,
     return DAG.getVectorShuffle(VT, DL, V1, V2, NewMask);
   }
 
-  if (SDValue NewShuffle = widenShuffleMask(DL, OrigMask, VT, V1, V2, DAG))
-    return NewShuffle;
-
   // Check for illegal shuffle mask element index values.
   int MaskUpperLimit = OrigMask.size() * (V2IsUndef ? 1 : 2);
   (void)MaskUpperLimit;