From: lkcl <lkcl@web>
Date: Fri, 22 Oct 2021 15:27:45 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~3555
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=581cab88c98394d41ce0c9914bf19d1fd45c5dd7;p=libreriscv.git

---

diff --git a/3d_gpu/architecture/dynamic_simd/simdscope.mdwn b/3d_gpu/architecture/dynamic_simd/simdscope.mdwn
index a81358c69..6eb194c06 100644
--- a/3d_gpu/architecture/dynamic_simd/simdscope.mdwn
+++ b/3d_gpu/architecture/dynamic_simd/simdscope.mdwn
@@ -27,7 +27,7 @@ SimdScope is used as follows:
         a = s.Signal(64)
         b = s.Signal(32)
 
-    with m.If(a > Const(2)):
+    with m.If(a > 2):
         m.d.comb += b.eq(a[:32])
 
 Note that the scalar parameter is selected from a runtime/compiletime
@@ -40,3 +40,17 @@ that **under no circumstances** shall SimdScope or SimdSignal alter
 the fundamental language behavioural characteristics of Type 1 (AST)
 or Type 2 (dsl.Module)
         
+Note that under some circumstances, particularly temporary intermediate
+results, it may be necessary to introduce explicit SimdShape instances
+containing elwid-specific element widths.  Relevant examples here include
+exponent and mantissa for IEEE754FP
+
+        expshape = SimdShape(part_shape={0b00: 11, # FP64
+                                         0b01: 8,  # FP32
+                                         0b10: 5,  # FP16
+                                         0b01: 8}  # BF16
+
+here, because SimdShape derives from Shape, things still work
+because SimdShape works out that its maximum scalar size is
+11, and sets Shape.width to 11 when SimdScope is set in
+scalar mode