Ever wondered which R functions are actually passed to internal C code? Well, wonder no more as it turns out there is an unexported named list within the methods package providing instructions for turning builtin and special functions into generic functions. Wrapping this list with names() gives us the list of all R functions which wrap calls to .Primitive().
names(methods:::.BasicFunsList)
# [1] "$" "$<-" "["
# [4] "[<-" "[[" "[[<-"
# [7] "%*%" "xtfrm" "c"
# [10] "all" "any" "sum"
# [13] "prod" "max" "min"
# [16] "range" "is.matrix" ">="
# [19] "cosh" "cummax" "dimnames<-"
# [22] "as.raw" "log2" "tan"
# [25] "dim" "as.logical" "^"
# [28] "is.finite" "sinh" "log10"
# [31] "as.numeric" "dim<-" "is.array"
# [34] "tanpi" "gamma" "atan"
# [37] "as.integer" "Arg" "signif"
# [40] "cumprod" "cos" "length"
# [43] "!=" "digamma" "exp"
# [46] "floor" "acos" "seq.int"
# [49] "abs" "length<-" "sqrt"
# [52] "!" "acosh" "is.nan"
# [55] "Re" "tanh" "names"
# [58] "cospi" "&" "anyNA"
# [61] "trunc" "cummin" "levels<-"
# [64] "*" "Mod" "|"
# [67] "names<-" "+" "log"
# [70] "lgamma" "as.complex" "asinh"
# [73] "-" "sin" "/"
# [76] "as.environment" "<=" "as.double"
# [79] "is.infinite" "is.numeric" "rep"
# [82] "round" "sinpi" "dimnames"
# [85] "asin" "as.character" "%/%"
# [88] "is.na" "<" ">"
# [91] "Im" "%%" "trigamma"
# [94] "==" "cumsum" "atanh"
# [97] "sign" "ceiling" "Conj"
# [100] "as.call" "log1p" "expm1"
# [103] "(" ":" "="
# [106] "@" "{" "~"
# [109] "&&" ".C" "baseenv"
# [112] "quote" "<-" "is.name"
# [115] "if" "||" "attr<-"
# [118] "untracemem" ".cache_class" "substitute"
# [121] "interactive" "is.call" "switch"
# [124] "function" "is.single" "is.null"
# [127] "is.language" "is.pairlist" ".External.graphics"
# [130] "globalenv" "class<-" ".Primitive"
# [133] "is.logical" "enc2utf8" "UseMethod"
# [136] ".subset" "proc.time" "enc2native"
# [139] "repeat" "<<-" "@<-"
# [142] "missing" "nargs" "isS4"
# [145] ".isMethodsDispatchOn" "forceAndCall" ".primTrace"
# [148] "storage.mode<-" ".Call" "unclass"
# [151] "gc.time" ".subset2" "environment<-"
# [154] "emptyenv" "seq_len" ".External2"
# [157] "is.symbol" "class" "on.exit"
# [160] "is.raw" "for" "is.complex"
# [163] "list" "invisible" "is.character"
# [166] "oldClass<-" "is.environment" "attributes"
# [169] "break" "return" "attr"
# [172] "tracemem" "next" ".Call.graphics"
# [175] "standardGeneric" "is.atomic" "retracemem"
# [178] "expression" "is.expression" "call"
# [181] "is.object" "pos.to.env" "attributes<-"
# [184] ".primUntrace" "...length" ".External"
# [187] "oldClass" ".Internal" ".Fortran"
# [190] "browser" "is.double" "while"
# [193] "nzchar" "is.list" "lazyLoadDBfetch"
# [196] "...elt" "is.integer" "is.function"
# [199] "is.recursive" "seq_along" "unlist"
# [202] "as.vector" "lengths"