From: lkcl <lkcl@web>
Date: Sun, 9 Oct 2022 21:31:53 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~121
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d6294c3c4304751f89b65db96c3edaaf3dd6de18;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls002/discussion.mdwn b/openpower/sv/rfc/ls002/discussion.mdwn
index 7abd96221..b95d8cef9 100644
--- a/openpower/sv/rfc/ls002/discussion.mdwn
+++ b/openpower/sv/rfc/ls002/discussion.mdwn
@@ -132,7 +132,11 @@ as a critical means of bootstrapping (constructing 64 bit addresses)
    What about fsub FRT,FRA,FRA?
 **
 
-That doesn't actually clear FRT to zero because NaN - NaN = Inf - Inf = NaN, not zero. Also, with round to -inf, 0 - 0 produces -0, not 0.
+That doesn't actually clear FRT to zero because `NaN - NaN` and
+`Inf - Inf` both equal `NaN`, not zero. Also, with "round to -inf",
+0 - 0 produces -0, not 0.  Thus use of `fsub` is critically
+dependent on the contents of registers and status flags, where
+`flis` is not.
 
 **
 5. "FRS" for both instructions should be changed to "FRT".  ("FRS" normally