Preclude UXLEN > SXLEN

riscv · Apr 28, 2023 · a84a261 · a84a261
1 parent 8cb9301
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diff --git a/src/machine.adoc b/src/machine.adoc
@@ -474,6 +474,9 @@ zero. Otherwise, it is a *WARL* field that encodes the current value of UXLEN.
 In particular, an implementation may make UXL be a read-only field whose
 value always ensures that UXLEN=MXLEN or UXLEN=SXLEN.
 
+The set of legal values that the SXL field may assume excludes those that would
+cause UXLEN to be greater than SXLEN.
+
 Whenever XLEN in any mode is set to a value less than the widest
 supported XLEN, all operations must ignore source operand register bits
 above the configured XLEN, and must sign-extend results to fill the

diff --git a/src/priv-preface.adoc b/src/priv-preface.adoc
@@ -36,7 +36,8 @@ version 1.12:
 
 * Defined the `misa`.V field to reflect that the V extension has been
 implemented.
-* Clarified that MXLEN&#8805;SXLEN.
+* Clarified that MXLEN&#8805;SXLEN, and added the constraint that
+SXLEN&#8805;UXLEN.
 
 *_Preface to Version 20211203_*