[SLP]Check that operand of abs does not overflow before making it par…

…t of minbitwidth transformation

Need to check that the operand of the abs intrinsic can be safely
truncated before making it part of the minbitwidth transformation.

Fixes llvm#112577

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -17224,9 +17224,25 @@ bool BoUpSLP::collectValuesToDemote(
                 MaskedValueIsZero(I->getOperand(1), Mask, SimplifyQuery(*DL)));
       });
     };
+    auto AbsChecker = [&](unsigned BitWidth, unsigned OrigBitWidth) {
+      assert(BitWidth <= OrigBitWidth && "Unexpected bitwidths!");
+      return all_of(E.Scalars, [&](Value *V) {
+        auto *I = cast<Instruction>(V);
+        unsigned SignBits = OrigBitWidth - BitWidth;
+        APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth - 1);
+        unsigned Op0SignBits =
+            ComputeNumSignBits(I->getOperand(0), *DL, 0, AC, nullptr, DT);
+        return SignBits <= Op0SignBits &&
+               ((SignBits != Op0SignBits &&
+                 !isKnownNonNegative(I->getOperand(0), SimplifyQuery(*DL))) ||
+                MaskedValueIsZero(I->getOperand(0), Mask, SimplifyQuery(*DL)));
+      });
+    };
     if (ID != Intrinsic::abs) {
       Operands.push_back(getOperandEntry(&E, 1));
       CallChecker = CompChecker;
+    } else {
+      CallChecker = AbsChecker;
     }
     InstructionCost BestCost =
         std::numeric_limits<InstructionCost::CostType>::max();

llvm/test/Transforms/SLPVectorizer/abs-overflow-incorrect-minbws.ll

@@ -8,8 +8,10 @@ define i32 @test(i32 %n) {
 ; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <2 x i32> poison, i32 [[N]], i32 0
 ; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <2 x i32> zeroinitializer
 ; CHECK-NEXT:    [[TMP2:%.*]] = add <2 x i32> [[TMP1]], <i32 1, i32 2>
-; CHECK-NEXT:    [[TMP3:%.*]] = mul <2 x i32> [[TMP2]], <i32 273837369, i32 273837369>
-; CHECK-NEXT:    [[TMP4:%.*]] = call <2 x i32> @llvm.abs.v2i32(<2 x i32> [[TMP3]], i1 false)
+; CHECK-NEXT:    [[TMP3:%.*]] = zext <2 x i32> [[TMP2]] to <2 x i64>
+; CHECK-NEXT:    [[TMP7:%.*]] = mul nuw nsw <2 x i64> [[TMP3]], <i64 273837369, i64 273837369>
+; CHECK-NEXT:    [[TMP8:%.*]] = call <2 x i64> @llvm.abs.v2i64(<2 x i64> [[TMP7]], i1 true)
+; CHECK-NEXT:    [[TMP4:%.*]] = trunc <2 x i64> [[TMP8]] to <2 x i32>
 ; CHECK-NEXT:    [[TMP5:%.*]] = extractelement <2 x i32> [[TMP4]], i32 0
 ; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <2 x i32> [[TMP4]], i32 1
 ; CHECK-NEXT:    [[RES1:%.*]] = add i32 [[TMP5]], [[TMP6]]