scc

commit 1b0107f059a35efdbef66890593f2913c6b460ee
parent 3801978b851d9c808f913c22ced53e1e9e3be46b
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Fri, 20 Mar 2015 05:20:55 +0000

Add optimization for SUB to

SUB accept the same optimizations that ADD, is only to change a
variable.

Diffstat:
M
cc2/cc2.h
 | 
3
++-
M
cc2/code.c
 | 
6
++++--
M
cc2/peep.c
 | 
5
++++-

3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/cc2/cc2.h b/cc2/cc2.h
@@ -134,7 +134,8 @@ enum {
 	RET,
 	NOP,
 	INC,
-	SUB
+	SUB,
+	DEC
 };
 
 enum {
diff --git a/cc2/code.c b/cc2/code.c
@@ -32,7 +32,8 @@ static void (*instcode[])(void) = {
 	[RET] = inst0,
 	[NOP] = inst0,
 	[INC] = inst1,
-	[SUB] = inst2
+	[SUB] = inst2,
+	[DEC] = inst1
 };
 
 static char *insttext[] = {
@@ -47,7 +48,8 @@ static char *insttext[] = {
 	[RET] = "RET",
 	[NOP] = "NOP",
 	[INC] = "INC",
-	[SUB] = "SUB"
+	[SUB] = "SUB",
+	[DEC] = "DEC"
 };
 
 Inst *pc, *prog;
diff --git a/cc2/peep.c b/cc2/peep.c
@@ -10,19 +10,22 @@ peephole(void)
 {
 	Addr to, from;
 	TINT i;
+	uint8_t op;
 
 	for (pc = prog; pc; pc = pc->next) {
 		to = pc->to;
 		from = pc->from;
 
 		switch (pc->op) {
+		case SUB:
 		case ADD:
 			if (from.kind == CONST) {
 				if ((i = from.u.i) == 0 || i < 4) {
 					delcode();
+					op = (pc->op == ADD) ? INC : DEC;
 
 					while (i--)
-						inscode(INC, &to, NULL);
+						inscode(op, &to, NULL);
 				}
 			/* TODO: More optimizations (ex: -1) */
 			}