[SLP]Fix minbitwidth analysis for gather nodes with icmp users.

If the node is not in MinBWs container and the user node is icmp node,
the compiler should not check the type size of the user instruction, it
is always 1 and is not good for actual bitwidth analysis.

Fixes llvm#105988

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -15975,6 +15975,10 @@ void BoUpSLP::computeMinimumValueSizes() {
                     auto It = MinBWs.find(TE);
                     if (It != MinBWs.end() && It->second.first > UserTESz)
                       return true;
+                    // The size of icmp is always 1 and should not be
+                    // considered.
+                    if (TE->getOpcode() == Instruction::ICmp)
+                      return true;
                     return DL->getTypeSizeInBits(U->getType()) > UserTESz;
                   }));
         })) {

llvm/test/Transforms/SLPVectorizer/X86/gather-with-cmp-user.ll

@@ -7,15 +7,13 @@ define i1 @test(i32 %g, i16 %d) {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    [[TMP0:%.*]] = and i16 [[D]], 1
 ; CHECK-NEXT:    [[XOR_I_I:%.*]] = xor i32 [[G]], 1
-; CHECK-NEXT:    [[TMP1:%.*]] = trunc i32 [[G]] to i8
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x i8> poison, i8 [[TMP1]], i32 0
-; CHECK-NEXT:    [[TMP3:%.*]] = trunc i32 [[XOR_I_I]] to i8
-; CHECK-NEXT:    [[TMP4:%.*]] = insertelement <2 x i8> [[TMP2]], i8 [[TMP3]], i32 1
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> poison, i32 [[G]], i32 0
+; CHECK-NEXT:    [[TMP9:%.*]] = insertelement <2 x i32> [[TMP1]], i32 [[XOR_I_I]], i32 1
+; CHECK-NEXT:    [[TMP4:%.*]] = trunc <2 x i32> [[TMP9]] to <2 x i8>
 ; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <2 x i8> [[TMP4]], <2 x i8> poison, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
 ; CHECK-NEXT:    [[TMP6:%.*]] = add <4 x i8> [[TMP5]], <i8 -9, i8 -9, i8 -1, i8 -1>
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp sgt <4 x i8> [[TMP6]], <i8 -3, i8 -3, i8 -3, i8 -3>
 ; CHECK-NEXT:    [[TMP8:%.*]] = zext <4 x i1> [[TMP7]] to <4 x i8>
-; CHECK-NEXT:    [[TMP9:%.*]] = sext <2 x i8> [[TMP4]] to <2 x i32>
 ; CHECK-NEXT:    [[TMP10:%.*]] = shufflevector <2 x i32> [[TMP9]], <2 x i32> poison, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
 ; CHECK-NEXT:    [[TMP11:%.*]] = zext <4 x i8> [[TMP8]] to <4 x i32>
 ; CHECK-NEXT:    [[TMP12:%.*]] = icmp sgt <4 x i32> [[TMP10]], [[TMP11]]