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package firrtl
package passes
import firrtl.ir._
import firrtl.PrimOps._
import firrtl.Mappers._
import firrtl.Utils.long_BANG
// Makes all implicit width extensions and truncations explicit
object PadWidths extends Pass {
def name = "Pad Widths"
private def width(t: Type): Int = long_BANG(t).toInt
private def width(e: Expression): Int = width(e.tpe)
// Returns an expression with the correct integer width
private def fixup(i: Int)(e: Expression) = {
def tx = e.tpe match {
case t: UIntType => UIntType(IntWidth(i))
case t: SIntType => SIntType(IntWidth(i))
// default case should never be reached
}
if (i > width(e)) {
DoPrim(Pad, Seq(e), Seq(i), tx)
} else if (i < width(e)) {
val e2 = DoPrim(Bits, Seq(e), Seq(i - 1, 0), UIntType(IntWidth(i)))
// Bit Select always returns UInt, cast if selecting from SInt
e.tpe match {
case UIntType(_) => e2
case SIntType(_) => DoPrim(AsSInt, Seq(e2), Seq.empty, SIntType(IntWidth(i)))
}
} else {
e
}
}
// Recursive, updates expression so children exp's have correct widths
private def onExp(e: Expression): Expression = {
val sensitiveOps = Seq( Lt, Leq, Gt, Geq, Eq, Neq, Not, And, Or, Xor,
Add, Sub, Mul, Div, Rem, Shr)
val x = e map onExp
x match {
case Mux(cond, tval, fval, tpe) => {
val tvalx = fixup(width(tpe))(tval)
val fvalx = fixup(width(tpe))(fval)
Mux(cond, tvalx, fvalx, tpe)
}
case DoPrim(op, args, consts, tpe) => op match {
case _ if sensitiveOps.contains(op) => {
val i = args.map(a => width(a)).foldLeft(0) {(a, b) => math.max(a, b)}
x map fixup(i)
}
case Dshl => {
// special case as args aren't all same width
val ax = fixup(width(tpe))(args(0))
DoPrim(Dshlw, Seq(ax, args(1)), consts, tpe)
}
case Shl => {
// special case as arg should be same width as result
val ax = fixup(width(tpe))(args(0))
DoPrim(Shlw, Seq(ax), consts, tpe)
}
case _ => x
}
case ValidIf(cond, value, tpe) => ValidIf(cond, fixup(width(tpe))(value), tpe)
case x => x
}
}
// Recursive. Fixes assignments and register initialization widths
private def onStmt(s: Statement): Statement = {
s map onExp match {
case s: Connect => {
val ex = fixup(width(s.loc))(s.expr)
Connect(s.info, s.loc, ex)
}
case s: DefRegister => {
val ex = fixup(width(s.tpe))(s.init)
DefRegister(s.info, s.name, s.tpe, s.clock, s.reset, ex)
}
case s => s map onStmt
}
}
private def onModule(m: DefModule): DefModule = {
m match {
case m: Module => Module(m.info, m.name, m.ports, onStmt(m.body))
case m: ExtModule => m
}
}
def run(c: Circuit): Circuit = Circuit(c.info, c.modules.map(onModule _), c.main)
}
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