[SLP]Fix PR88834: check if unsigned arg can be trunced, being used in smax/smin intrinsics.

Need to check that unsigned argument can be safely used in smax/smin
intrinsics by checking if at least single sign bit is cleared, otherwise
its value may be treated as negative instead of positive.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -14639,10 +14639,16 @@ bool BoUpSLP::collectValuesToDemote(
         assert((ID == Intrinsic::smin || ID == Intrinsic::smax) &&
                "Expected min/max intrinsics only.");
         unsigned SignBits = OrigBitWidth - BitWidth;
+        APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth - 1);
         return SignBits <= ComputeNumSignBits(I->getOperand(0), *DL, 0, AC,
                                               nullptr, DT) &&
+               (!isKnownNonNegative(I->getOperand(0), SimplifyQuery(*DL)) ||
+                MaskedValueIsZero(I->getOperand(0), Mask,
+                                  SimplifyQuery(*DL))) &&
                SignBits <= ComputeNumSignBits(I->getOperand(1), *DL, 0, AC,
-                                              nullptr, DT);
+                                              nullptr, DT) &&
+               (!isKnownNonNegative(I->getOperand(1), SimplifyQuery(*DL)) ||
+                MaskedValueIsZero(I->getOperand(1), Mask, SimplifyQuery(*DL)));
       });
     };
     if (ID != Intrinsic::abs) {

llvm/test/Transforms/SLPVectorizer/RISCV/smax-unsigned-operand.ll

@@ -9,11 +9,15 @@ define void @main(ptr noalias %p) {
 ; CHECK-LABEL: define void @main(
 ; CHECK-SAME: ptr noalias [[P:%.*]]) #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[CONV_4:%.*]] = zext i32 0 to i64
+; CHECK-NEXT:    [[COND_4:%.*]] = tail call i64 @llvm.smax.i64(i64 [[CONV_4]], i64 0)
+; CHECK-NEXT:    [[CONV5_4:%.*]] = trunc i64 [[COND_4]] to i8
+; CHECK-NEXT:    store i8 [[CONV5_4]], ptr getelementptr inbounds ([11 x i8], ptr @e, i64 0, i64 4), align 1
 ; CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[P]], align 4
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> <i32 0, i32 poison>, i32 [[TMP0]], i32 1
-; CHECK-NEXT:    [[TMP2:%.*]] = call <2 x i32> @llvm.smax.v2i32(<2 x i32> [[TMP1]], <2 x i32> <i32 0, i32 1>)
-; CHECK-NEXT:    [[TMP3:%.*]] = trunc <2 x i32> [[TMP2]] to <2 x i8>
-; CHECK-NEXT:    store <2 x i8> [[TMP3]], ptr getelementptr inbounds ([11 x i8], ptr @e, i64 0, i64 4), align 1
+; CHECK-NEXT:    [[CONV_5:%.*]] = zext i32 [[TMP0]] to i64
+; CHECK-NEXT:    [[COND_5:%.*]] = tail call i64 @llvm.smax.i64(i64 [[CONV_5]], i64 1)
+; CHECK-NEXT:    [[CONV5_5:%.*]] = trunc i64 [[COND_5]] to i8
+; CHECK-NEXT:    store i8 [[CONV5_5]], ptr getelementptr inbounds ([11 x i8], ptr @e, i64 0, i64 5), align 1
 ; CHECK-NEXT:    ret void
 ;
 bb: