[SLP]Fix PR90892: do a correct sign analysis of the entries elements in gather shuffles.

Need to do extra analysis of the scalar elements of the tree entry to be
shuffled instead of the vectorized value to correctly deduce signedness
info.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -11640,13 +11640,14 @@ class BoUpSLP::ShuffleInstructionBuilder final : public BaseShuffleAnalysis {
 
   /// Cast value \p V to the vector type with the same number of elements, but
   /// the base type \p ScalarTy.
-  Value *castToScalarTyElem(Value *V) {
+  Value *castToScalarTyElem(Value *V,
+                            std::optional<bool> IsSigned = std::nullopt) {
     auto *VecTy = cast<VectorType>(V->getType());
     if (VecTy->getElementType() == ScalarTy)
       return V;
     return Builder.CreateIntCast(
         V, VectorType::get(ScalarTy, VecTy->getElementCount()),
-        !isKnownNonNegative(V, SimplifyQuery(*R.DL)));
+        IsSigned ? *IsSigned : !isKnownNonNegative(V, SimplifyQuery(*R.DL)));
   }
 
 public:
@@ -11795,12 +11796,30 @@ class BoUpSLP::ShuffleInstructionBuilder final : public BaseShuffleAnalysis {
   /// Adds 2 input vectors (in form of tree entries) and the mask for their
   /// shuffling.
   void add(const TreeEntry &E1, const TreeEntry &E2, ArrayRef<int> Mask) {
-    add(E1.VectorizedValue, E2.VectorizedValue, Mask);
+    Value *V1 = E1.VectorizedValue;
+    if (V1->getType()->isIntOrIntVectorTy())
+      V1 = castToScalarTyElem(V1, all_of(E1.Scalars, [&](Value *V) {
+                                return !isKnownNonNegative(
+                                    V, SimplifyQuery(*R.DL));
+                              }));
+    Value *V2 = E2.VectorizedValue;
+    if (V2->getType()->isIntOrIntVectorTy())
+      V2 = castToScalarTyElem(V2, all_of(E2.Scalars, [&](Value *V) {
+                                return !isKnownNonNegative(
+                                    V, SimplifyQuery(*R.DL));
+                              }));
+    add(V1, V2, Mask);
   }
   /// Adds single input vector (in form of tree entry) and the mask for its
   /// shuffling.
   void add(const TreeEntry &E1, ArrayRef<int> Mask) {
-    add(E1.VectorizedValue, Mask);
+    Value *V1 = E1.VectorizedValue;
+    if (V1->getType()->isIntOrIntVectorTy())
+      V1 = castToScalarTyElem(V1, all_of(E1.Scalars, [&](Value *V) {
+                                return !isKnownNonNegative(
+                                    V, SimplifyQuery(*R.DL));
+                              }));
+    add(V1, Mask);
   }
   /// Adds 2 input vectors and the mask for their shuffling.
   void add(Value *V1, Value *V2, ArrayRef<int> Mask) {

llvm/test/Transforms/SLPVectorizer/RISCV/shuffled-gather-casted.ll

@@ -9,7 +9,7 @@ define i32 @test(ptr %p) {
 ; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <4 x i16> <i16 0, i16 poison, i16 0, i16 0>, i16 [[D_0]], i32 1
 ; CHECK-NEXT:    [[TMP1:%.*]] = or <4 x i16> [[TMP0]], zeroinitializer
 ; CHECK-NEXT:    [[TMP2:%.*]] = and <4 x i16> [[TMP1]], zeroinitializer
-; CHECK-NEXT:    [[TMP3:%.*]] = sext <4 x i16> [[TMP0]] to <4 x i32>
+; CHECK-NEXT:    [[TMP3:%.*]] = zext <4 x i16> [[TMP0]] to <4 x i32>
 ; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <4 x i32> [[TMP3]], <4 x i32> <i32 0, i32 poison, i32 0, i32 0>, <4 x i32> <i32 4, i32 1, i32 6, i32 7>
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp sgt <4 x i32> [[TMP4]], zeroinitializer
 ; CHECK-NEXT:    [[TMP6:%.*]] = select <4 x i1> [[TMP5]], <4 x i16> [[TMP2]], <4 x i16> <i16 0, i16 2, i16 0, i16 0>