[SLP]Do correct signedness analysis for externally used scalars

If the scalars is used externally is in the root node, it may have
incorrect signedness info because of the conflict with the demanded bits
analysis. Need to perform exact signedness analysis and compute it
rather than rely on the precomputed value, which might be incorrect for
alternate zext/sext nodes.

Fixes #113520

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -12068,8 +12068,9 @@ InstructionCost BoUpSLP::getTreeCost(ArrayRef<Value *> VectorizedVals) {
     auto It = MinBWs.find(Entry);
     if (It != MinBWs.end()) {
       auto *MinTy = IntegerType::get(F->getContext(), It->second.first);
-      unsigned Extend =
-          It->second.second ? Instruction::SExt : Instruction::ZExt;
+      unsigned Extend = isKnownNonNegative(EU.Scalar, SimplifyQuery(*DL))
+                            ? Instruction::ZExt
+                            : Instruction::SExt;
       VecTy = getWidenedType(MinTy, BundleWidth);
       ExtraCost = TTI->getExtractWithExtendCost(Extend, EU.Scalar->getType(),
                                                 VecTy, EU.Lane);
@@ -15784,8 +15785,9 @@ BoUpSLP::vectorizeTree(const ExtraValueToDebugLocsMap &ExternallyUsedValues,
           // to the larger type.
           ExV = Ex;
           if (Scalar->getType() != Ex->getType())
-            ExV = Builder.CreateIntCast(Ex, Scalar->getType(),
-                                        MinBWs.find(E)->second.second);
+            ExV = Builder.CreateIntCast(
+                Ex, Scalar->getType(),
+                !isKnownNonNegative(Scalar, SimplifyQuery(*DL)));
           auto *I = dyn_cast<Instruction>(Ex);
           ScalarToEEs[Scalar].try_emplace(I ? I->getParent()
                                             : &F->getEntryBlock(),

llvm/test/Transforms/SLPVectorizer/SystemZ/ext-alt-node-must-ext.ll

@@ -17,7 +17,7 @@ define i32 @test(ptr %0, ptr %1) {
 ; CHECK-NEXT:    [[TMP13:%.*]] = extractelement <2 x i8> [[TMP12]], i32 0
 ; CHECK-NEXT:    [[DOTNEG:%.*]] = sext i8 [[TMP13]] to i32
 ; CHECK-NEXT:    [[TMP15:%.*]] = extractelement <2 x i8> [[TMP12]], i32 1
-; CHECK-NEXT:    [[TMP8:%.*]] = sext i8 [[TMP15]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = zext i8 [[TMP15]] to i32
 ; CHECK-NEXT:    [[TMP10:%.*]] = add nsw i32 [[DOTNEG]], [[TMP8]]
 ; CHECK-NEXT:    ret i32 [[TMP10]]
 ;

llvm/test/Transforms/SLPVectorizer/resized-alt-shuffle-after-minbw.ll

@@ -80,7 +80,7 @@ define void @func(i32 %0) {
 ; CHECK-NEXT:    [[TMP75:%.*]] = extractelement <32 x i1> [[TMP20]], i32 4
 ; CHECK-NEXT:    [[TMP76:%.*]] = and i1 false, [[TMP75]]
 ; CHECK-NEXT:    [[TMP77:%.*]] = extractelement <32 x i32> [[TMP18]], i32 0
-; CHECK-NEXT:    [[TMP78:%.*]] = sext i32 [[TMP77]] to i64
+; CHECK-NEXT:    [[TMP78:%.*]] = zext i32 [[TMP77]] to i64
 ; CHECK-NEXT:    [[TMP79:%.*]] = getelementptr float, ptr addrspace(1) null, i64 [[TMP78]]
 ; CHECK-NEXT:    ret void
 ;