[x86] Fix yet another bug in the new vector shuffle lowering's handling

of widening masks.

We can't widen a zeroing mask unless both elements that would be merged
are either zeroed or undef. This is the only way to widen a mask if it
has a zeroed element.

Also clean up the code here by ordering the checks in a more logical way
and by using the symoblic values for undef and zero. I'm actually torn
on using the symbolic values because the existing code is littered with
the assumption that -1 is undef, and moreover that entries '< 0' are the
special entries. While that works with the values given to these
constants, using the symbolic constants actually makes it a bit more
opaque why this is the case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218575 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4678340b6fb1d9d13b78b682d2d110304d25da8a..09f0be0e2466d9c86923a96a5f133edbcdc80efc 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9875,27 +9875,36 @@ static SDValue lower256BitVectorShuffle(SDValue Op, SDValue V1, SDValue V2,
 static bool canWidenShuffleElements(ArrayRef<int> Mask,
                                     SmallVectorImpl<int> &WidenedMask) {
   for (int i = 0, Size = Mask.size(); i < Size; i += 2) {
-    // Check for any of the sentinel values (negative) and if they are the same,
-    // we can widen to that.
-    if (Mask[i] < 0 && Mask[i] == Mask[i + 1]) {
-      WidenedMask.push_back(Mask[i]);
+    // If both elements are undef, its trivial.
+    if (Mask[i] == SM_SentinelUndef && Mask[i + 1] == SM_SentinelUndef) {
+      WidenedMask.push_back(SM_SentinelUndef);
       continue;
     }
 
     // Check for an undef mask and a mask value properly aligned to fit with
     // a pair of values. If we find such a case, use the non-undef mask's value.
-    if (Mask[i] == -1 && Mask[i + 1] >= 0 && Mask[i + 1] % 2 == 1) {
+    if (Mask[i] == SM_SentinelUndef && Mask[i + 1] >= 0 && Mask[i + 1] % 2 == 1) {
       WidenedMask.push_back(Mask[i + 1] / 2);
       continue;
     }
-    if (Mask[i + 1] == -1 && Mask[i] >= 0 && Mask[i] % 2 == 0) {
+    if (Mask[i + 1] == SM_SentinelUndef && Mask[i] >= 0 && Mask[i] % 2 == 0) {
       WidenedMask.push_back(Mask[i] / 2);
       continue;
     }
 
+    // When zeroing, we need to spread the zeroing across both lanes to widen.
+    if (Mask[i] == SM_SentinelZero || Mask[i + 1] == SM_SentinelZero) {
+      if ((Mask[i] == SM_SentinelZero || Mask[i] == SM_SentinelUndef) &&
+          (Mask[i + 1] == SM_SentinelZero || Mask[i + 1] == SM_SentinelUndef)) {
+        WidenedMask.push_back(SM_SentinelZero);
+        continue;
+      }
+      return false;
+    }
+
     // Finally check if the two mask values are adjacent and aligned with
     // a pair.
-    if (Mask[i] != -1 && Mask[i] % 2 == 0 && Mask[i] + 1 == Mask[i + 1]) {
+    if (Mask[i] != SM_SentinelUndef && Mask[i] % 2 == 0 && Mask[i] + 1 == Mask[i + 1]) {
       WidenedMask.push_back(Mask[i] / 2);
       continue;
     }

diff --git a/test/CodeGen/X86/vector-shuffle-128-v16.ll b/test/CodeGen/X86/vector-shuffle-128-v16.ll
index 21806489815c749b9e142bba64b152d800488c16..db7091485bed2277b979272bcdfcada8e90ae59b 100644 (file)
--- a/test/CodeGen/X86/vector-shuffle-128-v16.ll
+++ b/test/CodeGen/X86/vector-shuffle-128-v16.ll
@@ -665,3 +665,40 @@ entry:
 
   ret <16 x i8> %shuffle
 }
+
+define <16 x i8> @stress_test2(<16 x i8> %s.0.0, <16 x i8> %s.0.1, <16 x i8> %s.0.2) {
+; SSSE3-LABEL: @stress_test2
+; SSSE3:       # BB#0:
+; SSSE3-NEXT:    pshufb {{.*}} # xmm0 = zero,zero,xmm0[2],zero,zero,zero,xmm0[11],zero,zero,xmm0[3,4,5],zero,zero,xmm0[15,5]
+; SSSE3-NEXT:    movdqa  %xmm1, %[[X1:xmm[0-9]+]]
+; SSSE3-NEXT:    pshufb {{.*}} # [[X1]] = [[X1]][13,14],zero,[[X1]][0,10,5],zero,[[X1]][10,10],zero,zero,zero,[[X1]][14,12],zero,zero
+; SSSE3-NEXT:    por     %xmm0, %[[X1]]
+; SSSE3-NEXT:    movdqa  %xmm2, %xmm0
+; SSSE3-NEXT:    pshufb {{.*}} # xmm0 = zero,zero,zero,zero,zero,zero,xmm0[1,6,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    movdqa  %xmm1, %[[X2:xmm[0-9]+]]
+; SSSE3-NEXT:    pshufb {{.*}} # [[X2]] = [[X2]][1,12,5,9,1,5],zero,zero,[[X2]][u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    por     %xmm0, %[[X2]]
+; SSSE3-NEXT:    pshufb {{.*}} # xmm1 = zero,zero,zero,xmm1[2],zero,zero,xmm1[6,15,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    pshufb {{.*}} # xmm2 = xmm2[15,8,12],zero,xmm2[13,15],zero,zero,xmm2[u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    por     %xmm1, %xmm2
+; SSSE3-NEXT:    punpcklbw {{.*}} # xmm2 = xmm2[0],[[X2]][0],xmm2[1],[[X2]][1],xmm2[2],[[X2]][2],xmm2[3],[[X2]][3],xmm2[4],[[X2]][4],xmm2[5],[[X2]][5],xmm2[6],[[X2]][6],xmm2[7],[[X2]][7]
+; SSSE3-NEXT:    movdqa  %xmm2, %[[X3:xmm[0-9]+]]
+; SSSE3-NEXT:    pshufb {{.*}} # [[X3]] = [[X3]][6],zero,[[X3]][14,14],zero,zero,[[X3]][11,0,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    movdqa  %[[X1]], %xmm0
+; SSSE3-NEXT:    pshufb {{.*}} # xmm0 = zero,xmm0[12],zero,zero,xmm0[1,14],zero,zero,xmm0[u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    por     %[[X3]], %xmm0
+; SSSE3-NEXT:    pshufb {{.*}} # xmm2 = zero,xmm2[u,2,3,u,u,u,u,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    movdqa  %[[X1]], %[[X3]]
+; SSSE3-NEXT:    pshufb {{.*}} # [[X3]] = [[X3]][3,u],zero,zero,[[X3]][u,u,u,u,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    por     %xmm2, %[[X3]]
+; SSSE3-NEXT:    pshufb {{.*}} # [[X1]] = [[X1]][1,4,10,13,u,u,u,u,u,u,u,u,u,u,u,u]
+; SSSE3-NEXT:    punpcklbw {{.*}} # [[X1]] = [[X1]][0],[[X3]][0],[[X1]][1],[[X3]][1],[[X1]][2],[[X3]][2],[[X1]][3],[[X3]][3],[[X1]][4],[[X3]][4],[[X1]][5],[[X3]][5],[[X1]][6],[[X3]][6],[[X1]][7],[[X3]][7]
+; SSSE3-NEXT:    punpcklbw {{.*}} # xmm0 = xmm0[0],[[X1]][0],xmm0[1],[[X1]][1],xmm0[2],[[X1]][2],xmm0[3],[[X1]][3],xmm0[4],[[X1]][4],xmm0[5],[[X1]][5],xmm0[6],[[X1]][6],xmm0[7],[[X1]][7]
+; SSSE3-NEXT:    retq
+entry:
+  %s.1.0 = shufflevector <16 x i8> %s.0.0, <16 x i8> %s.0.1, <16 x i32> <i32 29, i32 30, i32 2, i32 16, i32 26, i32 21, i32 11, i32 26, i32 26, i32 3, i32 4, i32 5, i32 30, i32 28, i32 15, i32 5>
+  %s.1.1 = shufflevector <16 x i8> %s.0.1, <16 x i8> %s.0.2, <16 x i32> <i32 31, i32 1, i32 24, i32 12, i32 28, i32 5, i32 2, i32 9, i32 29, i32 1, i32 31, i32 5, i32 6, i32 17, i32 15, i32 22>
+  %s.2.0 = shufflevector <16 x i8> %s.1.0, <16 x i8> %s.1.1, <16 x i32> <i32 22, i32 1, i32 12, i32 3, i32 30, i32 4, i32 30, i32 undef, i32 1, i32 10, i32 14, i32 18, i32 27, i32 13, i32 16, i32 19>
+
+  ret <16 x i8> %s.2.0
+}