[SLP]Fix detection of matching splat vector

Need to check, that the mask of the potentially matching splat node is
not less defined than the requested mask to avoid poison propagation and
incorrect code.

Fixes #135113

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -10617,7 +10617,11 @@ class BaseShuffleAnalysis {
                                /*IsStrict=*/true) ||
                 (Shuffle && Mask.size() == Shuffle->getShuffleMask().size() &&
                  Shuffle->isZeroEltSplat() &&
-                 ShuffleVectorInst::isZeroEltSplatMask(Mask, Mask.size())));
+                 ShuffleVectorInst::isZeroEltSplatMask(Mask, Mask.size()) &&
+                 all_of(enumerate(Mask), [&](const auto &P) {
+                   return P.value() == PoisonMaskElem ||
+                          Shuffle->getShuffleMask()[P.index()] == 0;
+                 })));
       }
       V = Op;
       return false;

llvm/test/Transforms/SLPVectorizer/X86/identity-match-splat-less-defined.ll

@@ -7,7 +7,8 @@ define i32 @test() {
 ; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <4 x i32> [[TMP1]], <4 x i32> poison, <4 x i32> <i32 0, i32 0, i32 0, i32 poison>
 ; CHECK-NEXT:    [[TMP3:%.*]] = or <4 x i32> [[TMP2]], <i32 0, i32 0, i32 0, i32 poison>
 ; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <4 x i32> [[TMP3]], <4 x i32> poison, <16 x i32> <i32 0, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2>
-; CHECK-NEXT:    [[TMP5:%.*]] = or <4 x i32> [[TMP2]], zeroinitializer
+; CHECK-NEXT:    [[TMP25:%.*]] = shufflevector <4 x i32> [[TMP2]], <4 x i32> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP5:%.*]] = or <4 x i32> [[TMP25]], zeroinitializer
 ; CHECK-NEXT:    [[TMP6:%.*]] = shufflevector <4 x i32> [[TMP5]], <4 x i32> poison, <24 x i32> <i32 0, i32 0, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 3, i32 3, i32 3>
 ; CHECK-NEXT:    [[TMP7:%.*]] = shufflevector <4 x i32> [[TMP3]], <4 x i32> poison, <64 x i32> <i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; CHECK-NEXT:    [[TMP8:%.*]] = shufflevector <4 x i32> [[TMP5]], <4 x i32> poison, <64 x i32> <i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 3, i32 3, i32 3, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>