[x86] Add another combine that is particularly useful for the new vector

shuffle lowering: match shuffle patterns equivalent to an unpcklwd or
unpckhwd instruction.

This allows us to use generic lowering code for v8i16 shuffles and match
the unpack pattern late.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212705 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 245cb414ca979ab8c3fcd39f063b4ed9e76deb1a..5ccff20e2943b3654ea1eb2b9fc32424ca902493 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -18694,6 +18694,47 @@ static SDValue PerformTargetShuffleCombine(SDValue N, SelectionDAG &DAG,
       return DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, V);
     }
 
+    // Look for shuffle patterns which can be implemented as a single unpack.
+    // FIXME: This doesn't handle the location of the PSHUFD generically, and
+    // only works when we have a PSHUFD followed by two half-shuffles.
+    if (Mask[0] == Mask[1] && Mask[2] == Mask[3] &&
+        (V.getOpcode() == X86ISD::PSHUFLW ||
+         V.getOpcode() == X86ISD::PSHUFHW) &&
+        V.getOpcode() != N.getOpcode() &&
+        V.hasOneUse()) {
+      SDValue D = V.getOperand(0);
+      while (D.getOpcode() == ISD::BITCAST && D.hasOneUse())
+        D = D.getOperand(0);
+      if (D.getOpcode() == X86ISD::PSHUFD && D.hasOneUse()) {
+        SmallVector<int, 4> VMask = getPSHUFShuffleMask(V);
+        SmallVector<int, 4> DMask = getPSHUFShuffleMask(D);
+        int NOffset = N.getOpcode() == X86ISD::PSHUFLW ? 0 : 4;
+        int VOffset = V.getOpcode() == X86ISD::PSHUFLW ? 0 : 4;
+        int WordMask[8];
+        for (int i = 0; i < 4; ++i) {
+          WordMask[i + NOffset] = Mask[i] + NOffset;
+          WordMask[i + VOffset] = VMask[i] + VOffset;
+        }
+        // Map the word mask through the DWord mask.
+        int MappedMask[8];
+        for (int i = 0; i < 8; ++i)
+          MappedMask[i] = 2 * DMask[WordMask[i] / 2] + WordMask[i] % 2;
+        const int UnpackLoMask[] = {0, 0, 1, 1, 2, 2, 3, 3};
+        const int UnpackHiMask[] = {4, 4, 5, 5, 6, 6, 7, 7};
+        if (std::equal(std::begin(MappedMask), std::end(MappedMask),
+                       std::begin(UnpackLoMask)) ||
+            std::equal(std::begin(MappedMask), std::end(MappedMask),
+                       std::begin(UnpackHiMask))) {
+          // We can replace all three shuffles with an unpack.
+          V = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, D.getOperand(0));
+          DCI.AddToWorklist(V.getNode());
+          return DAG.getNode(MappedMask[0] == 0 ? X86ISD::UNPCKL
+                                                : X86ISD::UNPCKH,
+                             DL, MVT::v8i16, V, V);
+        }
+      }
+    }
+
     break;
 
   case X86ISD::PSHUFD:

diff --git a/test/CodeGen/X86/vector-shuffle-128-v16.ll b/test/CodeGen/X86/vector-shuffle-128-v16.ll
index 71fac00021ff1c60cfe1bc93b938eb51dc4f1d5d..4da7e42caabf635983a5c2d94f9751b3b85492a6 100644 (file)
--- a/test/CodeGen/X86/vector-shuffle-128-v16.ll
+++ b/test/CodeGen/X86/vector-shuffle-128-v16.ll
@@ -44,14 +44,22 @@ define <16 x i8> @shuffle_v16i8_00_00_00_00_01_01_01_01_02_02_02_02_03_03_03_03(
 ; CHECK-SSE2-LABEL: @shuffle_v16i8_00_00_00_00_01_01_01_01_02_02_02_02_03_03_03_03
 ; CHECK-SSE2:       # BB#0:
 ; CHECK-SSE2-NEXT:    punpcklbw %xmm0, %xmm0
-; CHECK-SSE2-NEXT:    pshufd {{.*}} # xmm0 = xmm0[0,1,2,1]
-; CHECK-SSE2-NEXT:    pshuflw {{.*}} # xmm0 = xmm0[0,0,1,1,4,5,6,7]
-; CHECK-SSE2-NEXT:    pshufhw {{.*}} # xmm0 = xmm0[0,1,2,3,6,6,7,7]
+; CHECK-SSE2-NEXT:    punpcklwd %xmm0, %xmm0
 ; CHECK-SSE2-NEXT:    retq
   %shuffle = shufflevector <16 x i8> %a, <16 x i8> %b, <16 x i32> <i32 0, i32 0, i32 0, i32 0, i32 1, i32 1, i32 1, i32 1, i32 2, i32 2, i32 2, i32 2, i32 3, i32 3, i32 3, i32 3>
   ret <16 x i8> %shuffle
 }
 
+define <16 x i8> @shuffle_v16i8_04_04_04_04_05_05_05_05_06_06_06_06_07_07_07_07(<16 x i8> %a, <16 x i8> %b) {
+; CHECK-SSE2-LABEL: @shuffle_v16i8_04_04_04_04_05_05_05_05_06_06_06_06_07_07_07_07
+; CHECK-SSE2:       # BB#0:
+; CHECK-SSE2-NEXT:    punpcklbw %xmm0, %xmm0
+; CHECK-SSE2-NEXT:    punpckhwd %xmm0, %xmm0
+; CHECK-SSE2-NEXT:    retq
+  %shuffle = shufflevector <16 x i8> %a, <16 x i8> %b, <16 x i32> <i32 4, i32 4, i32 4, i32 4, i32 5, i32 5, i32 5, i32 5, i32 6, i32 6, i32 6, i32 6, i32 7, i32 7, i32 7, i32 7>
+  ret <16 x i8> %shuffle
+}
+
 define <16 x i8> @shuffle_v16i8_00_00_00_00_04_04_04_04_08_08_08_08_12_12_12_12(<16 x i8> %a, <16 x i8> %b) {
 ; CHECK-SSE2-LABEL: @shuffle_v16i8_00_00_00_00_04_04_04_04_08_08_08_08_12_12_12_12
 ; CHECK-SSE2:       # BB#0: