From 900c04de9530c30e38caca24ac19273f45b705ce Mon Sep 17 00:00:00 2001 From: lkcl Date: Wed, 15 Sep 2021 17:51:20 +0100 Subject: [PATCH] --- openpower/sv/svp64/appendix.mdwn | 39 -------------------------------- 1 file changed, 39 deletions(-) diff --git a/openpower/sv/svp64/appendix.mdwn b/openpower/sv/svp64/appendix.mdwn index 1a528809d..25bf3b641 100644 --- a/openpower/sv/svp64/appendix.mdwn +++ b/openpower/sv/svp64/appendix.mdwn @@ -160,45 +160,6 @@ This is equivalent to followed by `llvm.masked.expandload.*` -# Rounding, clamp and saturate - -see [[av_opcodes]]. - -To help ensure that audio quality is not compromised by overflow, -"saturation" is provided, as well as a way to detect when saturation -occurred if desired (Rc=1). When Rc=1 there will be a *vector* of CRs, -one CR per element in the result (Note: this is different from VSX which -has a single CR per block). - -When N=0 the result is saturated to within the maximum range of an -unsigned value. For integer ops this will be 0 to 2^elwidth-1. Similar -logic applies to FP operations, with the result being saturated to -maximum rather than returning INF, and the minimum to +0.0 - -When N=1 the same occurs except that the result is saturated to the min -or max of a signed result, and for FP to the min and max value rather -than returning +/- INF. - -When Rc=1, the CR "overflow" bit is set on the CR associated with the -element, to indicate whether saturation occurred. Note that due to -the hugely detrimental effect it has on parallel processing, XER.SO is -**ignored** completely and is **not** brought into play here. The CR -overflow bit is therefore simply set to zero if saturation did not occur, -and to one if it did. - -Note also that saturate on operations that produce a carry output are -prohibited due to the conflicting use of the CR.so bit for storing if -saturation occurred. - -Post-analysis of the Vector of CRs to find out if any given element hit -saturation may be done using a mapreduced CR op (cror), or by using the -new crweird instruction, transferring the relevant CR bits to a scalar -integer and testing it for nonzero. see [[sv/cr_int_predication]] - -Note that the operation takes place at the maximum bitwidth (max of -src and dest elwidth) and that truncation occurs to the range of the -dest elwidth. - # Reduce mode Reduction in SVP64 is deterministic and somewhat of a misnomer. A normal -- 2.30.2