From 5ac280026e50ec85289d153ff4eaa04f0591c60b Mon Sep 17 00:00:00 2001
From: David Given <dg@cowlark.com>
Date: Thu, 7 Feb 2019 00:06:32 +0100
Subject: [PATCH] Experimentally use rst 1 to optimise frame variable loads.
 Reduces Star Trek from 43892 to 43205 bytes.

---
 mach/i80/libem/rst.s     | 29 +++++++++++++++++++++++++++++
 mach/i80/ncg/table       | 28 +++++++++++++++++++++-------
 plat/cpm/boot.s          |  6 ++++++
 plat/cpm/build-pkg.lua   |  5 ++++-
 plat/cpm/build-tools.lua |  3 +++
 5 files changed, 63 insertions(+), 8 deletions(-)
 create mode 100644 mach/i80/libem/rst.s

diff --git a/mach/i80/libem/rst.s b/mach/i80/libem/rst.s
new file mode 100644
index 000000000..b4ad39bee
--- /dev/null
+++ b/mach/i80/libem/rst.s
@@ -0,0 +1,29 @@
+#
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+.sect .text
+
+.define .rst_init
+.rst_init:
+    mvi a, 0xc3     ! jmp <a16>
+    sta 0x08
+    lxi h, rst1
+    shld 0x09
+    ret
+
+    ! de = [bc+const2] (remember bc is the frame pointer)
+rst1:
+    pop h
+    mov e, m
+    inx h
+    mov d, m
+    inx h
+    push h
+    xchg        ! hl = offset
+    dad b
+    mov e, m
+    inx h
+    mov d, m
+    ret
diff --git a/mach/i80/ncg/table b/mach/i80/ncg/table
index 0368b31e3..4101d2772 100644
--- a/mach/i80/ncg/table
+++ b/mach/i80/ncg/table
@@ -82,6 +82,8 @@ INSTRUCTIONS
 /* cpo	label:ro			cost(3,14).	*/
 /* cz	label:ro			cost(3,14).	*/
 /* daa			kills a:cc	cost(1, 4).	*/
+   data1 ".data1" const1:ro.
+   data2 ".data2" const2:ro.
    dad	b_d_h_sp:ro 	kills hl:cc	cost(1,10).
    dcr	reg+lbreg:rw:cc			cost(1, 5).
    dcr	m:rw:cc				cost(1, 7).
@@ -129,7 +131,7 @@ INSTRUCTIONS
 /* rpe					cost(1, 8).	*/
 /* rpo					cost(1, 8).	*/
    rrc			kills a:cc	cost(1, 4).
-/* rst	const1:ro			cost(1,11).	*/
+   rst	const1:ro kills a:cc cost(1,11).	
 /* rz					cost(1, 8).	*/
    sbb	reg1:ro 	kills a:cc	cost(1, 4).
 /* sbi	const1:ro 	kills a:cc	cost(2, 7).	*/
@@ -241,12 +243,24 @@ pat loc					yields {const2,$1}
 pat ldc					yields {const2,highw($1)}
 					       {const2,loww($1)}
 
-pat lol
-uses hlreg={const2,$1}, dereg
-gen dad lb
-    mov e,{m}
-    inx hl
-    mov d,{m}				yields de
+#ifdef USE_I80_RSTS
+   pat lol
+      kills hlreg
+      uses hlreg, dereg
+      gen
+         rst {const1, 1}
+         data2 {const2, $1}
+      yields de
+#else
+   pat lol
+      uses hlreg={const2, $1}, dereg
+      gen
+         dad lb
+         mov e,{m}
+         inx hl
+         mov d,{m}
+      yields de
+#endif
 
 pat loe
 uses hlreg
diff --git a/plat/cpm/boot.s b/plat/cpm/boot.s
index 960dc400d..40ab0d775 100644
--- a/plat/cpm/boot.s
+++ b/plat/cpm/boot.s
@@ -48,6 +48,12 @@ begtext:
 
 	lxi sp, stack + STACKSIZE
 
+	! Initialise the rsts (if desired).
+
+	#ifdef USE_I80_RSTS
+		call .rst_init
+	#endif
+
 	! C-ify the command line at 0x0080.
 	
 	lxi h, 0x0080
diff --git a/plat/cpm/build-pkg.lua b/plat/cpm/build-pkg.lua
index 0a4da3be0..59c9f806a 100644
--- a/plat/cpm/build-pkg.lua
+++ b/plat/cpm/build-pkg.lua
@@ -4,7 +4,10 @@ include("lang/build.lua")
 ackfile {
 	name = "boot",
 	srcs = { "./boot.s" },
-	vars = { plat = "cpm" }
+	vars = {
+		plat = "cpm",
+		["+ackcflags"] = "-DUSE_I80_RSTS",
+	}
 }
 
 build_plat_libs {
diff --git a/plat/cpm/build-tools.lua b/plat/cpm/build-tools.lua
index 383cf8c17..25d1b1327 100644
--- a/plat/cpm/build-tools.lua
+++ b/plat/cpm/build-tools.lua
@@ -8,6 +8,9 @@ build_as {
 build_ncg {
 	name = "ncg",
 	arch = "i80",
+	vars = {
+		["+cflags"] = "-DUSE_I80_RSTS"
+	}
 }
 
 build_top {