From 2b0629f87f0cb590aaf9e4e78d3bf73bd0d511f0 Mon Sep 17 00:00:00 2001
From: David Given <dg@cowlark.com>
Date: Wed, 6 Feb 2019 16:06:07 +0100
Subject: [PATCH] Common out boilerplate function prologue code; shrinks Star
 Trek from 44256 to 43892 bytes.

---
 mach/i80/libem/pro.s | 58 ++++++++++++++++++++++++++++++++++++++++++++
 mach/i80/ncg/mach.c  | 26 +++++++++-----------
 2 files changed, 69 insertions(+), 15 deletions(-)
 create mode 100644 mach/i80/libem/pro.s

diff --git a/mach/i80/libem/pro.s b/mach/i80/libem/pro.s
new file mode 100644
index 000000000..05976358e
--- /dev/null
+++ b/mach/i80/libem/pro.s
@@ -0,0 +1,58 @@
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+.sect .text
+
+.define .proword, .probyte
+.define .pro0, .pro2, .pro4
+
+! BC is used as the frame pointer, but HL and DE can be corrupted.
+
+.proword:
+	pop h
+	push b
+	mov e, m
+	inx h
+	mov d, m
+	inx h
+	jmp .pron
+
+.probyte:
+	pop h
+	push b
+	mvi e, 0xff
+	mov d, m
+	inx h
+	jmp .pron
+
+.pro4:
+	pop h
+	push b
+	lxi d, -4
+	jmp .pron
+
+.pro2:
+	pop h
+	push b
+	lxi d, -2
+	jmp .pron
+
+.pro0:
+	pop h
+	push b
+	lxi d, 0
+	! fall through
+.pron:
+	shld .retadr
+	! Copy the current stack pointer to BC.
+	lxi h, 0
+	dad sp
+	mov b, h
+	mov c, l
+	! Calculate the new stack pointer.
+	dad d
+	sphl
+	lhld .retadr
+	pchl
+
diff --git a/mach/i80/ncg/mach.c b/mach/i80/ncg/mach.c
index 6bae01350..a01c11eec 100644
--- a/mach/i80/ncg/mach.c
+++ b/mach/i80/ncg/mach.c
@@ -52,22 +52,18 @@ void con_mult(sz) word sz;
 #define FL_MSB_AT_LOW_ADDRESS 0
 #include <con_float>
 
-void prolog(nlocals) full nlocals;
+void prolog(full nlocals)
 {
-
-	fprintf(codefile, "\tpush\tb\n\tlxi\th,0\n\tdad\tsp\n\tmov\tb,h\n\tmov\tc,l\n");
-	switch (nlocals)
-	{
-		case 4:
-			fprintf(codefile, "\tpush\th\n");
-		case 2:
-			fprintf(codefile, "\tpush\th\n");
-		case 0:
-			break;
-		default:
-			fprintf(codefile, "\tlxi\th,%d\n\tdad\tsp\n\tsphl\n", -nlocals);
-			break;
-	}
+	if (nlocals == 0)
+		fprintf(codefile, "\tcall .pro0\n");
+	else if (nlocals == 2)
+		fprintf(codefile, "\tcall .pro2\n");
+	else if (nlocals == 4)
+		fprintf(codefile, "\tcall .pro4\n");
+	else if (nlocals < 0x100)
+		fprintf(codefile, "\tcall .probyte\n\t.data1 %d\n", -nlocals);
+	else
+		fprintf(codefile, "\tcall .proword\n\t.data2 %d\n", -nlocals);
 }
 
 void mes(type) word type;