trying to emulate a stack for add and sub

3 files changed, 18 insertions, 7 deletions

diff --git a/crenshaw/README b/crenshaw/README
index 0d1e58d..7bad3b5 100644
--- a/crenshaw/README
+++ b/crenshaw/README
@@ -1,7 +1,8 @@
 fpc main.pas 
 ./main < test.prog > test.asm
 nasm -f elf32 test.asm
-gcc -m32 -o test test.o
+gcc -m32 -march=i486 -ffreestanding -o test test.o
+objcopy -O binary --only-section=.text test test.bin
 ndisasm -b32 test.bin
 ./test
 
diff --git a/crenshaw/main.pas b/crenshaw/main.pas
index eff412c..677c496 100644
--- a/crenshaw/main.pas
+++ b/crenshaw/main.pas
@@ -75,30 +75,40 @@ end;
 procedure Term;
 begin
 	EmitLn('mov eax, ' + GetNum);
+	EmitLn('push eax');
 end;
 
 procedure Add;
 begin;
 	Match('+');
 	Term;
+	Emitln('pop eax');
+	EmitLn('pop ebx');
 	EmitLn('add eax, ebx');
+	EmitLn('push eax');
 end;
 
 procedure Subtract;
 begin;
 	Match('-');
 	Term;
+	EmitLn('pop eax');
+	EmitLn('pop ebx');
 	EmitLn('sub eax, ebx');
+	EmitLn('neg eax');
+	EmitLn('push eax');
 end;
 
 procedure Expression;
 begin
 	Term;
-	EmitLn('mov ebx, eax');
-	case Look of
-		'+': Add;
-		'-': Subtract;
-	else Expected('+/-');
+	while Look in ['+', '-'] do
+	begin
+		case Look of
+			'+': Add;
+			'-': Subtract;
+		else Expected('+/-');
+		end;
 	end;
 end;
 
diff --git a/crenshaw/test.prog b/crenshaw/test.prog
index d6c68c4..a490d4b 100644
--- a/crenshaw/test.prog
+++ b/crenshaw/test.prog
@@ -1,2 +1,2 @@
-4+2
+4+2+5-8