From add3b6629bce008feab69da236fdb1f42c11583c Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Tue, 14 Apr 2020 14:59:01 -0400
Subject: [PATCH] Make DO .. LOOP binary code more compact
Only a few bytes saved in forth1.bin, but the DO .. LOOP construct
isn't used much yet. It's still significant savings per LOOP call.
---
forth/core.fs | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/forth/core.fs b/forth/core.fs
index a9b44a9..bdf4012 100644
--- a/forth/core.fs
+++ b/forth/core.fs
@@ -94,12 +94,20 @@
H@
; IMMEDIATE
+( Increase loop counter and returns whether we should loop. )
+: _
+ R> ( IP, keep for later )
+ R> 1 + ( ip i+1 )
+ DUP >R ( ip i )
+ I' = ( ip f )
+ SWAP >R ( f )
+;
+
( One could think that we should have a sub word to avoid all
these COMPILE, but we can't because otherwise it messes with
the RS )
: LOOP
- COMPILE R> 1 LITN COMPILE + COMPILE DUP COMPILE >R
- COMPILE I' COMPILE = COMPILE (?br)
+ COMPILE _ COMPILE (?br)
H@ - ,
COMPILE R> COMPILE DROP COMPILE R> COMPILE DROP
; IMMEDIATE