From: lkcl <lkcl@web>
Date: Fri, 18 Dec 2020 19:32:16 +0000 (+0000)
Subject: (no commit message)
X-Git-Tag: convert-csv-opcode-to-binary~1217
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=ecbe96541e1c961d90b8016101672831433777e3;p=libreriscv.git

---

diff --git a/3d_gpu/architecture/dynamic_simd/logicops.mdwn b/3d_gpu/architecture/dynamic_simd/logicops.mdwn
index 76b867614..f64f91f12 100644
--- a/3d_gpu/architecture/dynamic_simd/logicops.mdwn
+++ b/3d_gpu/architecture/dynamic_simd/logicops.mdwn
@@ -12,8 +12,41 @@ These are not the same as bitwise operations equivslent to:
 
 they are instead SIMD versions of:
 
-     result = 0 # initial value
+     result = 0 # initial value (single bit)
      for i in range(64):
          result = result or a[i]
 
+# bool (some operator) as an example
 
+instead of the above single 64 bit bool result, dynamic partitioned SIMD must return a batch of results.   if the subdivision is 2x32 it is:
+
+     result[0] = 0 # initial value for low word
+     result[1] = 0 # initial value for hi word
+     for i in range(32):
+         result[0] = result[0] or a[i]
+         result[1] = result[1] or a[i+32]
+
+and likewise by the time 8x8 is reached:
+
+     for j in range(8):
+         result[j] = 0 # initial value for each byte
+         for i in range(8):
+             result[j] = result[j] or a[i+j*8]
+
+now the question becomes: what to do when the Signal is dynamically partitionable? how do we merge all of the combinations, 1x64 2x32 4x16 8x8 into the same statically-allocated hardware?
+
+the first thing is to define some conventions, that the answer (result) will always be 8 bit (not 1 bit) and that, rather than just one bit being set if sone are set, all 8 bits are clear or all 8 bits are set.
+
+likewise, when configured as 2x32 the result is subdivided into two 4 bit halves: the first half is all zero if all the first 32 bits are zero, and all ones if any one bit in the first 32 bits are set.
+
+     result[0] = 0 # initial value for low word
+     result[4] = 0 # initial value for hi word
+     for i in range(32):
+         result[0] = result[0] or a[i]
+         result[4] = result[4] or a[i+32]
+     if result[0]:
+         result[1:3] = 1
+     if result[4]:
+         result[5:7] = 1
+
+thus we have a convention where