[InstCombine] Missed optimization for icmp(constants[x]) when the range of x is implied

[XChy]

@constant = constant [4 x i32] [i32 1, i32 2, i32 3, i32 4]

define i32 @src(i64 %x) local_unnamed_addr #0 {
entry:
    %cond = icmp ult i64 %x, 2
    br i1 %cond, label %case1, label %case2

case2:
    ret i32 789

case1:
    %isOK_ptr = getelementptr inbounds i32, ptr @constant, i64 %x
    %isOK = load i32, ptr %isOK_ptr, align 1
    %cond_inferred = icmp ult i32 %isOK, 5
    br i1 %cond_inferred, label %caseOK, label %caseErr

caseOK:
    ret i32 456

caseErr:
    ret i32 123
}

Here %cond_inferred should be always true.
Missed example
alive-tv

[XChy]

Candidate patch.