diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/main/scala/chisel3/util/Lookup.scala | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/src/main/scala/chisel3/util/Lookup.scala b/src/main/scala/chisel3/util/Lookup.scala index 9e909c0c..1152bdb4 100644 --- a/src/main/scala/chisel3/util/Lookup.scala +++ b/src/main/scala/chisel3/util/Lookup.scala @@ -4,6 +4,28 @@ package chisel3.util import chisel3._ +/** For each element in a list, muxes (looks up) between cases (one per list element) based on a + * common address. + * + * @note This appears to be an odd, specialized operator that we haven't seen used much, and seems + * to be a holdover from chisel2. This may be deprecated and removed, usage is not + * recommended. + * + * @param addr common select for cases, shared (same) across all list elements + * @param default default value for each list element, should the address not match any case + * @param mapping list of cases, where each entry consists of a [[chisel3.util.BitPat BitPath]] (compared against addr) and + * a list of elements (same length as default) that is the output value for that + * element (will have the same index in the output). + * + * @example {{{ + * ListLookup(2.U, // address for comparison + * List(10.U, 11.U, 12.U), // default "row" if none of the following cases match + * Array(BitPat(2.U) -> List(20.U, 21.U, 22.U), // this "row" hardware-selected based off address 2.U + * BitPat(3.U) -> List(30.U, 31.U, 32.U)) + * ) // hardware-evaluates to List(20.U, 21.U, 22.U) + * // Note: if given address 0.U, the above would hardware evaluate to List(10.U, 11.U, 12.U) + * }}} + */ object ListLookup { def apply[T <: Data](addr: UInt, default: List[T], mapping: Array[(BitPat, List[T])]): List[T] = { val map = mapping.map(m => (m._1 === addr, m._2)) @@ -13,6 +35,18 @@ object ListLookup { } } +/** Muxes between cases based on whether an address matches any pattern for a case. + * Similar to [[chisel3.util.MuxLookup MuxLookup]], but uses [[chisel3.util.BitPat BitPat]] for address comparison. + * + * @note This appears to be an odd, specialized operator that we haven't seen used much, and seems + * to be a holdover from chisel2. This may be deprecated and removed, usage is not + * recommended. + * + * @param addr address to select between cases + * @param default default value should the address not match any case + * @param mapping list of cases, where each entry consists of a [[chisel3.util.BitPat BitPat]] (compared against addr) and the + * output value if the BitPat matches + */ object Lookup { def apply[T <: Bits](addr: UInt, default: T, mapping: Seq[(BitPat, T)]): T = ListLookup(addr, List(default), mapping.map(m => (m._1, List(m._2))).toArray).head |