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Diffstat (limited to 'src/rv32.tex')
| -rw-r--r-- | src/rv32.tex | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/src/rv32.tex b/src/rv32.tex index 54bbaba..b1bcaca 100644 --- a/src/rv32.tex +++ b/src/rv32.tex @@ -1158,6 +1158,9 @@ FENCE. \hline 0000 & \em none & Normal Fence \\ \hline +\multirow{2}{*}{1000} & \multirow{2}{*}{TSO} & With FENCE RW,RW: exclude write-to-read ordering \\ + & & Otherwise: \em Reserved for future use. \\ +\hline \multicolumn{2}{|c|}{\em other} & \em Reserved for future use. \\ \hline \end{tabular} @@ -1171,6 +1174,20 @@ The fence mode field {\em fm} defines the semantics of the FENCE. A FENCE with {\em fm}=0000 orders all memory operations in its predecessor set before all memory operations in its successor set. +The optional FENCE.TSO instruction with {\em fm}=1000 orders all load +operations in its predecessor set before all memory operations in its +successor set, and all store operations in its predecessor set before +all store operations in its successor set. This leaves non-AMO store +operations in the FENCE.TSO's predecessor set unordered with non-AMO +loads in its successor set. + +\begin{commentary} + The FENCE.TSO encoding was added as an optional extension to the + original base FENCE instruction encoding. The base definition + requires that implementations ignore any set bits and treat the + FENCE as global, and so this is a backwards-compatible extension. +\end{commentary} + The unused fields in the FENCE instructions---{\em rs1} and {\em rd}---are reserved for finer-grain fences in future extensions. For forward compatibility, base implementations shall ignore these fields, and standard |