From 128093cf097815486ca59fac7b5a50523667b368 Mon Sep 17 00:00:00 2001
From: d6 <d_m@plastic-idolatry.com>
Date: Tue, 18 Jan 2022 00:10:12 -0500
Subject: [PATCH] update

---
 bfloat16.tal | 63 +++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 47 insertions(+), 16 deletions(-)

diff --git a/bfloat16.tal b/bfloat16.tal
index 4cf8060..91bd5fa 100644
--- a/bfloat16.tal
+++ b/bfloat16.tal
@@ -37,6 +37,16 @@
 ( -inf         1 11111111  0000000 negative infinity              )
 ( nan          * 11111111  ******* lots of nans; * is wild        )
 ( )
+( Some hex constants: )
+(      0 #0000 )
+(     -0 #8000 )
+(      1 #3f80 )
+(     -1 #bf80 )
+(      2 #4000 )
+(   +inf #7f80 )
+(   -inf #ff80 )
+(    nan #ffff (among others) )
+( )
 ( This code doesn't distinguish between quiet and signaling NaNs. )
 ( )
 ( Bfloat16 values are emitted in a hexadecimal format:            )
@@ -172,6 +182,19 @@
 @non-zero ( x* -> bool^ )
     #7fff AND2 #0000 NEQ2 JMP2r
 
+@is-nan ( x* -> bool^ )
+    #7fff AND2 #7f80 GTH2 JMP2r
+
+@non-nan ( x* -> bool^ )
+    #7fff AND2 #7f81 LTH2 JMP2r
+
+@is-inf ( x* -> bool^ )
+    #7fff AND2 #7f80 EQU2 JMP2r
+
+( not nan, not +/-inf )
+@is-finite ( x* -> bool^ )
+    #7fff AND2 #7f80 LTH2 JMP2r
+
 ( Shift mantissa m right by n bits, with rounding         )
 ( )
 ( We round differently depending on the value to be lost: )
@@ -207,22 +230,7 @@
     &rnd-up ( [mta n] )
     STH2r SFT INC JMP2r
 
-@is-nan ( x* -> bool^ )
-    SWP ( xlo xhi )
-    #7f ANDk ( xlo xhi 7f xhi&7f )
-    EQU ( xlo xhi xhi&7f=7f )
-    NIP SWP #00 NEQ ( xhi&7f=7f xlo!=0 )
-    AND JMP2r
-
-@non-nan ( x* -> bool^ )
-    #00 EQU STH ( xhi [xlo=0] )
-    #7f ANDk NEQ ( xhi 7f!=xhi&7f [xlo=0] )
-    NIP STHr ORA ( 7f!=xhi&7f|xlo=0 )
-    JMP2r
-
-@add-bf16 ( x* y* -> z* )
-    DUP2 ;non-nan
-
+( lift an integer byte into a bfloat16 value )
 @byte-to-bf16 ( n^ -> x* )
     #86 SWP ( exp n )
     &loop
@@ -298,4 +306,27 @@
 (   5.      inf + x  =  inf   )
 (   6.     -inf + x  = -inf   )
 @add-bf16 ( x* y* -> z* )
+    DUP2 ;is-nan JMP2 STH SWP2 
+    DUP2 ;is-nan JMP2 STH SWP2
+    STH2r ORA ,&nan JCN ( is lhs or rhs nan? )
+
+    DUP2 ;is-inf ,&rhs-inf JCN ( is rhs inf? )
+    SWP2 ;is-inf ,&lhs-inf JCN ( is lhs inf? )
+
+    ( TODO: determine exponent, round, and add )
+    ( stack is [rhs lhs] but order doesn't matter )
+
     JMP2r
+
+    &nan POP2 POP2 #ffff JMP2r
+    &rhs-inf SWP2 #8000 EOR2 EQUk ,&nan JCN POP2 JMP2r
+    &lhs-inf SWP2 POP2 JMP2r
+
+( TODO )
+( lots of stuff including: )
+( - subtraction )
+( - multiplication )
+( - division )
+( - floor/ceil/round )
+( - min/max )
+( - log2/exp2 )