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// See LICENSE for license details.
package chisel3.core
import scala.language.experimental.macros
import chisel3.internal._
import chisel3.internal.Builder.pushCommand
import chisel3.internal.firrtl._
import chisel3.internal.sourceinfo.{SourceInfo}
object when { // scalastyle:ignore object.name
/** Create a `when` condition block, where whether a block of logic is
* executed or not depends on the conditional.
*
* @param cond condition to execute upon
* @param block logic that runs only if `cond` is true
*
* @example
* {{{
* when ( myData === UInt(3) ) {
* // Some logic to run when myData equals 3.
* } .elsewhen ( myData === UInt(1) ) {
* // Some logic to run when myData equals 1.
* } .otherwise {
* // Some logic to run when myData is neither 3 nor 1.
* }
* }}}
*/
def apply(cond: Bool)(block: => Unit)(implicit sourceInfo: SourceInfo): WhenContext = {
new WhenContext(sourceInfo, cond, !cond, block)
}
}
/** Internal mechanism for generating a when. Because of the way FIRRTL
* commands are emitted, generating a FIRRTL elsewhen or nested whens inside
* elses would be difficult. Instead, this keeps track of the negative of the
* previous conditions, so when an elsewhen or otherwise is used, it checks
* that both the condition is true and all the previous conditions have been
* false.
*/
final class WhenContext(sourceInfo: SourceInfo, cond: Bool, prevCond: => Bool, block: => Unit) {
/** This block of logic gets executed if above conditions have been false
* and this condition is true.
*/
def elsewhen (elseCond: Bool)(block: => Unit)(implicit sourceInfo: SourceInfo): WhenContext = {
new WhenContext(sourceInfo, prevCond && elseCond, prevCond && !elseCond, block)
}
/** This block of logic gets executed only if the above conditions were all
* false. No additional logic blocks may be appended past the `otherwise`.
*/
def otherwise(block: => Unit)(implicit sourceInfo: SourceInfo): Unit =
new WhenContext(sourceInfo, prevCond, null, block)
pushCommand(WhenBegin(sourceInfo, cond.ref))
block
pushCommand(WhenEnd(sourceInfo))
}
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