From 9553eb26b2aa29de6a8a50eaa889e9839ad44bee Mon Sep 17 00:00:00 2001
From: John Wickerson <j.wickerson@imperial.ac.uk>
Date: Tue, 30 Jun 2020 20:56:26 +0000
Subject: Update on Overleaf.

---
 verilog.tex | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'verilog.tex')

diff --git a/verilog.tex b/verilog.tex
index 709781f..67f2f4e 100644
--- a/verilog.tex
+++ b/verilog.tex
@@ -2,7 +2,7 @@
 
 Verilog is a hardware description language commonly used to design hardware.  A Verilog design can then be synthesised into more basic logic which describes how different gates connect to each other, called a netlist.  This representation can then be put onto either a field-programmable gate array (FPGA) or turned into an application-specific integrated circuit (ASPIC) to implement the design that was described in Verilog.  The Verilog standard is quite large though, and not all Verilog features are needed to be able to describe hardware.  Many Verilog features are only useful for simulation and do not affect the actual hardware itself, which means that these features do not have to be modelled in the semantics.  In addition to that, as the HLS algorithm dictates which Verilog constructs are generated, meaning the Verilog subset that has to be modelled by the semantics can be reduced even further to only support the constructs that are needed.  Only supporting a smaller subset in the semantics also means that there is less chance that the standard is misunderstood, and that the semantics actually model how the Verilog is simulated.
 
-The Verilog semantics are based on the semantics proposed by \citet{loow19_verif_compil_verif_proces}, which were used to create a formal translation from HOL logic into a Verilog circuit.  These semantics are quite practical as they restrict themselves to a small subset of Verilog, which can nonetheless be used to model all hardware constructs one would want to design.  The main syntax for the Verilog subset is the following: \JW{This verilog syntax looks weird to me. I didn't think there was a `then' keyword, for instance. Perhaps you're aiming more at some sort of abstracted syntax of Verilog? What does the semicolon on its own mean? Some sort of skip statement? The case statement looks weird too -- how do you get multiple cases in a single switch statement, and where is the default case? }\YH{I think I have fixed most cases, yes the single semicolon is a skip statement, should I make that more obvious by naming it? }
+The Verilog semantics are based on the semantics proposed by \citet{loow19_verif_compil_verif_proces}, which were used to create a formal translation from HOL logic into a Verilog circuit.  These semantics are quite practical as they restrict themselves to a small subset of Verilog, which can nonetheless be used to model all hardware constructs one would want to design.  The main syntax for the Verilog subset is the following: \JW{This verilog syntax looks weird to me. I didn't think there was a `then' keyword, for instance. Perhaps you're aiming more at some sort of abstracted syntax of Verilog? What does the semicolon on its own mean? Some sort of skip statement? The case statement looks weird too -- how do you get multiple cases in a single switch statement, and where is the default case? }\YH{I think I have fixed most cases, yes the single semicolon is a skip statement, should I make that more obvious by naming it? } \JW{It still looks a bit funny to me -- a bit of a halfway-house between `proper' Verilog syntax and `abstract' Verilog syntax. E.g. the way `begin...end' blocks contain exactly two statements, or the way that you get an erroneous double semicolon by combining the `begin...end' rule with the `e=e;' rule. People who are very familiar with C-like syntax will know that this isn't quite right... but then again, it doesn't really matter whether you handle the full syntax, because you only have to pretty-print a subset of it. So, why not stick here with a slightly abstracted Verilog syntax? It would make the operational semantics easier to read, for instance. Basically like you had it before, but explicitly labelled as a simplified syntax, so readers don't get confused!}
 
 \begin{align*}
   v\quad ::=&\; \mathit{sz} \yhkeyword{'d} n\\
@@ -66,7 +66,7 @@ The two main evaluation functions are then \textit{erun}, which takes in the cur
 %  \inferrule[Nonblocking Array]{\yhkeyword{name}\ \textit{lhs} = \yhkeyword{OK}\ n \\ \textit{erun}\  \Gamma\ \textit{rhs}\ v_{\textit{rhs}}}{\textit{srun}\  (\Gamma_{r}, \Gamma_{a}, \Delta_{r}, \Delta_{a})\ (\textit{lhs} \Leftarrow \textit{rhs})\ (\Gamma_{r}, \Gamma_{a}, \Delta_{r} // \{n \rightarrow v_{\textit{rhs}}\}, \Delta_{a})}
 \end{gather*}
 
-\YH{TODO: Add rules for blocking and nonblocking assignment to arrays.}
+\YH{TODO: Add rules for blocking and nonblocking assignment to arrays.} \JW{CaseNoMatch and CaseMatch rules both have a mismatched parenthesis.} \JW{In CondTrue and CondFalse, the relationship between $\Gamma_0$ and $\sigma_0$ needs clarifying.} \JW{CaseNoMatch is missing the `default:' and `endcase' keywords.} \JW{In CaseNoMatch, it feels weird to me that you keep evaluating $e$ for each case of the switch, rather than just once at the start of the switch statement. I guess it's ok because a failed match doesn't change the state. Just a bit quirky, I guess.} \JW{In CaseDefault, I was slightly surprised to see `Some' -- is that necessary?} \JW{In BlockingReg, erun is taking more parameters than it does elsewhere.} \JW{When using subscripted variables like $\Gamma_r$, I prefer $\Gamma_{\rm r}$ because $r$ is a fixed name (short for `register'), not a variable.}
 
 Taking the \textsc{CondTrue} rule as an example, this rule will only apply if the Boolean result of running the expression results in a \texttt{true} value.  It then also states that the statement in the true branch of the conditional statement \textit{stt} runs from state $\sigma_{0}$ to state $\sigma_{1}$.  If both of these conditions hold, we then get that the conditional statement will also run from state $\sigma_{0}$ to state $\sigma_{1}$.  The \textsc{Blocking} and \textsc{Nonblocking} rules are a bit more interesting, as these modify the blocking and nonblocking association maps respectively.
 
-- 
cgit 

