diff options
| author | Schuyler Eldridge | 2021-07-07 21:05:33 -0400 |
|---|---|---|
| committer | GitHub | 2021-07-08 01:05:33 +0000 |
| commit | f1e37900170124254f3cf4599a45e7a485c17a91 (patch) | |
| tree | b2d1f0b809b53e309df080d68048c75184f6c1d5 /core | |
| parent | 558df41db062a14f52617fc44edd0aff569afa67 (diff) | |
Update docs on dontTouch as optimization barrier (#2015)
Change the Scaladoc for the dontTouch utility. Indicate that this is an
_optimization barrier_ and not just a guarantee that the signal won't be
removed. The optimization barrier interpretation is the current
implementation in the Scala FIRRTL Compiler.
Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
Diffstat (limited to 'core')
| -rw-r--r-- | core/src/main/scala/chisel3/dontTouch.scala | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/core/src/main/scala/chisel3/dontTouch.scala b/core/src/main/scala/chisel3/dontTouch.scala index 0487a567..e679f1a4 100644 --- a/core/src/main/scala/chisel3/dontTouch.scala +++ b/core/src/main/scala/chisel3/dontTouch.scala @@ -5,7 +5,8 @@ package chisel3 import chisel3.experimental.{ChiselAnnotation, annotate, requireIsHardware} import firrtl.transforms.DontTouchAnnotation -/** Marks that a signal should not be removed by Chisel and Firrtl optimization passes +/** Marks that a signal is an optimization barrier to Chisel and the FIRRTL compiler. This has the effect of + * guaranteeing that a signal will not be removed. * * @example {{{ * class MyModule extends Module { @@ -21,9 +22,11 @@ import firrtl.transforms.DontTouchAnnotation * @note Calling this on [[Data]] creates an annotation that Chisel emits to a separate annotations * file. This file must be passed to FIRRTL independently of the `.fir` file. The execute methods * in [[chisel3.Driver]] will pass the annotations to FIRRTL automatically. + * @note Because this is an optimization barrier, constants will not be propagated through a signal marked as + * dontTouch. */ object dontTouch { - /** Marks a signal to be preserved in Chisel and Firrtl + /** Mark a signal as an optimization barrier to Chisel and FIRRTL. * * @note Requires the argument to be bound to hardware * @param data The signal to be marked |