remove mistaken impliciation that lkcl is the only author

[libreriscv.git] / simple_v_extension / appendix.mdwn

diff --git a/simple_v_extension/appendix.mdwn b/simple_v_extension/appendix.mdwn
index a951d4450663125307b76c5d5feff09a609c16c3..c29044cfea6b9772be22c43d9b8dc3d968f819ee 100644 (file)
--- a/simple_v_extension/appendix.mdwn
+++ b/simple_v_extension/appendix.mdwn
@@ -1,4 +1,8 @@
-# Simple-V (Parallelism Extension Proposal) Appendix
+[[!oldstandards]]
+
+# Simple-V (Parallelism Extension Proposal) Appendix (OBSOLETE)
+
+**OBSOLETE**
 
 * Copyright (C) 2017, 2018, 2019 Luke Kenneth Casson Leighton
 * Status: DRAFTv0.6
@@ -194,7 +198,9 @@ comprehensive in its effect on instructions.
 Branch operations are augmented slightly to be a little more like FP
 Compares (FEQ, FNE etc.), by permitting the cumulation (and storage)
 of multiple comparisons into a register (taken indirectly from the predicate
-table).  As such, "ffirst" - fail-on-first - condition mode can be enabled.
+table) and enhancing them to branch "consensually" depending on *multiple*
+tests.  "ffirst" - fail-on-first - condition mode can also be enabled,
+to terminate the comparisons early.
 See ffirst mode in the Predication Table section.
 
 There are two registers for the comparison operation, therefore there
@@ -232,6 +238,13 @@ element tests must be performed (and the result optionally stored in
 the result mask), with a "post-analysis" phase carried out which checks
 whether to branch.
 
+Note also that whilst it may seem excessive to have all four (because
+conditional comparisons may be inverted by swapping src1 and src2),
+data-dependent fail-on-first is *not* invertible and *only* terminates
+on first zero-condition encountered.  Additionally it may be inconvenient
+to have to swap the predicate registers associated with src1 and src2,
+because this involves a new VBLOCK Context.
+
 ### Standard Branch <a name="standard_branch"></a>
 
 Branch operations use standard RV opcodes that are reinterpreted to
@@ -1087,7 +1100,7 @@ Note:
   is also marked as scalar, this is how the compatibility with
   standard RV LOAD/STORE is preserved by this algorithm.
 
-### Example Tables showing LOAD elements
+### Example Tables showing LOAD elements <a name="load_example"></a>
 
 This section contains examples of vectorised LOAD operations, showing
 how the two stage process works (three if zero/sign-extension is included).
@@ -1447,7 +1460,7 @@ circumstances it is perfectly fine to simply have the lanes
 "inactive" for predicated elements, even though it results in
 less than 100% ALU utilisation.
 
-## Twin-predication (based on source and destination register)
+## Twin-predication (based on source and destination register) <a name="tpred"></a>
 
 Twin-predication is not that much different, except that that
 the source is independently zero-predicated from the destination.