[SLP]Fix signedness analysis for scalars in graph.

Cannot use the sign info for the roots for all scalars in the graph,
need to perform the analysis for each particular scalar (tree node).

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -13182,8 +13182,23 @@ void BoUpSLP::computeMinimumValueSizes() {
     collectValuesToDemote(Roots.pop_back_val(), Expr, ToDemote, Roots);
 
   // Finally, map the values we can demote to the maximum bit with we computed.
-  for (auto *Scalar : ToDemote)
-    MinBWs.try_emplace(Scalar, MaxBitWidth, !IsKnownPositive);
+  DenseMap<const TreeEntry *, bool> Signendness;
+  for (auto *Scalar : ToDemote) {
+    bool IsSigned = true;
+    if (auto *TE = getTreeEntry(Scalar)) {
+      auto It = Signendness.find(TE);
+      if (It != Signendness.end()) {
+        IsSigned = It->second;
+      } else {
+        IsSigned = any_of(TE->Scalars, [&](Value *R) {
+          KnownBits Known = computeKnownBits(R, *DL);
+          return !Known.isNonNegative();
+        });
+        Signendness.try_emplace(TE, IsSigned);
+      }
+    }
+    MinBWs.try_emplace(Scalar, MaxBitWidth, IsSigned);
+  }
 }
 
 PreservedAnalyses SLPVectorizerPass::run(Function &F, FunctionAnalysisManager &AM) {

llvm/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll

@@ -295,9 +295,9 @@ define i32 @gather_reduce_8x16_i64(ptr nocapture readonly %a, ptr nocapture read
 ; GENERIC-NEXT:    [[A_ADDR_0101:%.*]] = phi ptr [ [[INCDEC_PTR58:%.*]], [[FOR_BODY]] ], [ [[A:%.*]], [[FOR_BODY_PREHEADER]] ]
 ; GENERIC-NEXT:    [[INCDEC_PTR58]] = getelementptr inbounds i16, ptr [[A_ADDR_0101]], i64 8
 ; GENERIC-NEXT:    [[TMP0:%.*]] = load <8 x i16>, ptr [[A_ADDR_0101]], align 2
-; GENERIC-NEXT:    [[TMP1:%.*]] = sext <8 x i16> [[TMP0]] to <8 x i32>
+; GENERIC-NEXT:    [[TMP1:%.*]] = zext <8 x i16> [[TMP0]] to <8 x i32>
 ; GENERIC-NEXT:    [[TMP2:%.*]] = load <8 x i16>, ptr [[B:%.*]], align 2
-; GENERIC-NEXT:    [[TMP3:%.*]] = sext <8 x i16> [[TMP2]] to <8 x i32>
+; GENERIC-NEXT:    [[TMP3:%.*]] = zext <8 x i16> [[TMP2]] to <8 x i32>
 ; GENERIC-NEXT:    [[TMP4:%.*]] = sub nsw <8 x i32> [[TMP1]], [[TMP3]]
 ; GENERIC-NEXT:    [[TMP5:%.*]] = extractelement <8 x i32> [[TMP4]], i64 0
 ; GENERIC-NEXT:    [[TMP6:%.*]] = sext i32 [[TMP5]] to i64
@@ -368,9 +368,9 @@ define i32 @gather_reduce_8x16_i64(ptr nocapture readonly %a, ptr nocapture read
 ; KRYO-NEXT:    [[A_ADDR_0101:%.*]] = phi ptr [ [[INCDEC_PTR58:%.*]], [[FOR_BODY]] ], [ [[A:%.*]], [[FOR_BODY_PREHEADER]] ]
 ; KRYO-NEXT:    [[INCDEC_PTR58]] = getelementptr inbounds i16, ptr [[A_ADDR_0101]], i64 8
 ; KRYO-NEXT:    [[TMP0:%.*]] = load <8 x i16>, ptr [[A_ADDR_0101]], align 2
-; KRYO-NEXT:    [[TMP1:%.*]] = sext <8 x i16> [[TMP0]] to <8 x i32>
+; KRYO-NEXT:    [[TMP1:%.*]] = zext <8 x i16> [[TMP0]] to <8 x i32>
 ; KRYO-NEXT:    [[TMP2:%.*]] = load <8 x i16>, ptr [[B:%.*]], align 2
-; KRYO-NEXT:    [[TMP3:%.*]] = sext <8 x i16> [[TMP2]] to <8 x i32>
+; KRYO-NEXT:    [[TMP3:%.*]] = zext <8 x i16> [[TMP2]] to <8 x i32>
 ; KRYO-NEXT:    [[TMP4:%.*]] = sub nsw <8 x i32> [[TMP1]], [[TMP3]]
 ; KRYO-NEXT:    [[TMP5:%.*]] = extractelement <8 x i32> [[TMP4]], i64 0
 ; KRYO-NEXT:    [[TMP6:%.*]] = sext i32 [[TMP5]] to i64

llvm/test/Transforms/SLPVectorizer/AArch64/getelementptr.ll

@@ -235,9 +235,9 @@ define void @test_i16_extend(ptr %p.1, ptr %p.2, i32 %idx.i32) {
 ; CHECK-NEXT:    [[T53:%.*]] = getelementptr inbounds i16, ptr [[P_1:%.*]], i64 [[IDX_0]]
 ; CHECK-NEXT:    [[T56:%.*]] = getelementptr inbounds i16, ptr [[P_2:%.*]], i64 [[IDX_0]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = load <8 x i16>, ptr [[T53]], align 2
-; CHECK-NEXT:    [[TMP2:%.*]] = sext <8 x i16> [[TMP1]] to <8 x i32>
+; CHECK-NEXT:    [[TMP2:%.*]] = zext <8 x i16> [[TMP1]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP3:%.*]] = load <8 x i16>, ptr [[T56]], align 2
-; CHECK-NEXT:    [[TMP4:%.*]] = sext <8 x i16> [[TMP3]] to <8 x i32>
+; CHECK-NEXT:    [[TMP4:%.*]] = zext <8 x i16> [[TMP3]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP5:%.*]] = sub nsw <8 x i32> [[TMP2]], [[TMP4]]
 ; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <8 x i32> [[TMP5]], i64 0
 ; CHECK-NEXT:    [[TMP7:%.*]] = sext i32 [[TMP6]] to i64