Upstream intervals (#870)

Major features:

- Added Interval type, as well as PrimOps asInterval, clip, wrap, and sqz.
- Changed PrimOp names: bpset -> setp, bpshl -> incp, bpshr -> decp
- Refactored width/bound inferencer into a separate constraint solver
- Added transforms to infer, trim, and remove interval bounds
- Tests for said features

Plan to be released with 1.3

1 files changed, 26 insertions, 4 deletions

diff --git a/src/main/antlr4/FIRRTL.g4 b/src/main/antlr4/FIRRTL.g4
index be15ab7c..518cb698 100644
--- a/src/main/antlr4/FIRRTL.g4
+++ b/src/main/antlr4/FIRRTL.g4
@@ -50,6 +50,7 @@ type
   : 'UInt' ('<' intLit '>')?
   | 'SInt' ('<' intLit '>')?
   | 'Fixed' ('<' intLit '>')? ('<' '<' intLit '>' '>')?
+  | 'Interval' (lowerBound boundValue boundValue upperBound)? ('.' intLit)?
   | 'Clock'
   | 'AsyncReset'
   | 'Reset'
@@ -187,6 +188,23 @@ intLit
   | HexLit
   ;
 
+lowerBound
+  : '['
+  | '('
+  ;
+
+upperBound
+  : ']'
+  | ')'
+  ;
+
+boundValue
+  : '?'
+  | DoubleLit
+  | UnsignedInt
+  | SignedInt
+  ;
+
 // Keywords that are also legal ids
 keywordAsId
   : 'circuit'
@@ -253,6 +271,8 @@ primop
   | 'asAsyncReset('
   | 'asSInt('
   | 'asClock('
+  | 'asFixedPoint('
+  | 'asInterval('
   | 'shl('
   | 'shr('
   | 'dshl('
@@ -270,10 +290,12 @@ primop
   | 'bits('
   | 'head('
   | 'tail('
-  | 'asFixedPoint('
-  | 'bpshl('
-  | 'bpshr('
-  | 'bpset('
+  | 'incp('
+  | 'decp('
+  | 'setp('
+  | 'wrap('
+  | 'clip('
+  | 'squz('
   ;
 
 /*------------------------------------------------------------------