[ValueTracking] Add logic for isKnownNonZero(umax X, Y)

`(umax X, Y) != 0` -> `X != 0 || Y != 0`

Alive2 Link:
    https://alive2.llvm.org/ce/z/_Z9AUT

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D149415

Author: goldsteinn

llvm/lib/Analysis/ValueTracking.cpp

@@ -2936,6 +2936,7 @@ bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
         return isNonZeroAdd(DemandedElts, Depth, Q, BitWidth,
                             II->getArgOperand(0), II->getArgOperand(1),
                             /*NSW*/ true);
+      case Intrinsic::umax:
       case Intrinsic::uadd_sat:
         if (isKnownNonZero(II->getArgOperand(0), DemandedElts, Depth, Q) ||
             isKnownNonZero(II->getArgOperand(1), DemandedElts, Depth, Q))

llvm/test/Analysis/ValueTracking/known-non-zero.ll

@@ -961,10 +961,7 @@ define i1 @umax_nonzero(i8 %xx, i8 %yy, i8 %ind) {
 ; CHECK-LABEL: @umax_nonzero(
 ; CHECK-NEXT:    [[X_NZ:%.*]] = icmp ne i8 [[XX:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[X_NZ]])
-; CHECK-NEXT:    [[X:%.*]] = call i8 @llvm.umax.i8(i8 [[XX]], i8 [[YY:%.*]])
-; CHECK-NEXT:    [[Z:%.*]] = or i8 [[X]], [[IND:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[Z]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %x_nz = icmp ne i8 %xx, 0
   call void @llvm.assume(i1 %x_nz)

llvm/test/Transforms/LoopVectorize/interleaved-accesses.ll

@@ -483,10 +483,10 @@ define void @even_load_dynamic_tc(ptr noalias nocapture readonly %A, ptr noalias
 ; CHECK-LABEL: @even_load_dynamic_tc(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[UMAX:%.*]] = call i64 @llvm.umax.i64(i64 [[N:%.*]], i64 2)
-; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[UMAX]], -1
-; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP0]], 8
+; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[UMAX]], 9
 ; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
 ; CHECK:       vector.ph:
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[UMAX]], -1
 ; CHECK-NEXT:    [[TMP1:%.*]] = lshr i64 [[TMP0]], 1
 ; CHECK-NEXT:    [[TMP2:%.*]] = add nuw i64 [[TMP1]], 1
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = and i64 [[TMP2]], 3