From 3382536f605735113b1ef619af71b122666638f7 Mon Sep 17 00:00:00 2001 From: lkcl Date: Mon, 5 Sep 2022 15:38:10 +0100 Subject: [PATCH] --- openpower/sv/normal.mdwn | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/openpower/sv/normal.mdwn b/openpower/sv/normal.mdwn index 817c41367..86ae3b4de 100644 --- a/openpower/sv/normal.mdwn +++ b/openpower/sv/normal.mdwn @@ -28,7 +28,8 @@ Modes apply to Arithmetic and Logical SVP64 operations: *VL is altered as a result*. * **sat mode** or saturation: clamps each element result to a min/max rather than overflows / wraps. allows signed and unsigned clamping for both INT and FP. -* **reduce mode**. a mapreduce is performed. the result is a scalar. a result vector however is required, as the upper elements may be used to store intermediary computations. the result of the mapreduce is in the first element with a nonzero predicate bit. see [[svp64/appendix]] +* **reduce mode**. if used correftly, a mapreduce (or a prefix sum) + is performed. see [[svp64/appendix]]: note that there are comprehensive caveats when using this mode. * **pred-result** will test the result (CR testing selects a bit of CR and inverts it, just like branch conditional testing) and if the test fails it is as if the @@ -47,7 +48,6 @@ The Mode table for Arithmetic and Logical operations | --- | --- |---------|-------------------------- | | 00 | 0 | dz sz | simple mode | | 00 | 1 | 0 RG | scalar reduce mode (mapreduce), SUBVL=1 | -| 00 | 1 | 1 / | parallel reduce mode (mapreduce), SUBVL=1 | | 00 | 1 | SVM 0 | subvector reduce mode, SUBVL>1 | | 00 | 1 | SVM 1 | Pack/Unpack mode, SUBVL>1 | | 01 | inv | CR-bit | Rc=1: ffirst CR sel | @@ -131,6 +131,8 @@ the appearance and effect of a Horizontal Vector Reduction. Due to the unusual decoupling it is also possible to perform prefix-sum in certain circumstances. Details are in the [[svp64/appendix]] +Reduce Mode should not be confused with Parallel Reduction [[sv/remap]]. + # Fail-on-first Data-dependent fail-on-first has two distinct variants: one for LD/ST, -- 2.30.2