[SLP]Fix bitwidth analysis for signed nodes, incoming into UITOFP nodes

If the signed node is the operand of UITOFP, the bitwidth analysis
should consider minimum value between incoming bitwidth and the bitwidth
of the UITOFP node.

Fixes #129244

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -18423,6 +18423,14 @@ void BoUpSLP::computeMinimumValueSizes() {
       return Known.isNonNegative();
     });
 
+    if (!IsKnownPositive && !IsTopRoot && E.UserTreeIndex &&
+        E.UserTreeIndex.UserTE->hasState() &&
+        E.UserTreeIndex.UserTE->getOpcode() == Instruction::UIToFP)
+      MaxBitWidth =
+          std::min(DL->getTypeSizeInBits(
+                       E.UserTreeIndex.UserTE->Scalars.front()->getType()),
+                   DL->getTypeSizeInBits(ScalarTy));
+
     // We first check if all the bits of the roots are demanded. If they're not,
     // we can truncate the roots to this narrower type.
     for (Value *Root : E.Scalars) {

llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll

@@ -7,7 +7,8 @@ define i32 @test(ptr %d, i32 %0) {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> poison, i32 [[TMP0]], i32 0
 ; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <2 x i32> [[TMP1]], <2 x i32> poison, <2 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP3:%.*]] = uitofp <2 x i32> [[TMP2]] to <2 x double>
+; CHECK-NEXT:    [[TMP8:%.*]] = sext <2 x i32> [[TMP2]] to <2 x i64>
+; CHECK-NEXT:    [[TMP3:%.*]] = uitofp <2 x i64> [[TMP8]] to <2 x double>
 ; CHECK-NEXT:    [[TMP4:%.*]] = fdiv <2 x double> [[TMP3]], zeroinitializer
 ; CHECK-NEXT:    [[TMP5:%.*]] = fcmp ogt <2 x double> [[TMP4]], zeroinitializer
 ; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <2 x i1> [[TMP5]], i32 1