duskos

commit de8b1611f450bdd710910ed225639d4863fd25eb
parent 72a6f120e181b8ee1ec55ee1777d0fd0a180d378
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Thu,  2 Jun 2022 16:30:14 -0400

TIL about x86's SETcc

Diffstat:
M
dusk.asm
 | 
24
+++++++++++++-----------

1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/dusk.asm b/dusk.asm
@@ -476,28 +476,30 @@ defword 'xor', 3, word_xor, word_or
 	ret
 
 defword 'not', 3, word_not, word_xor
-	sub dword [ebp],1	; carry=1 if 0
-set_PS_to_carry:		; set PS top to 0 or one depending on CF
-	lahf				; c = bit 0
-	mov al, ah
-	and eax, 1
-	mov [ebp], eax
+	mov eax, [ebp]
+	mov dword [ebp], 0
+	test eax, eax
+	setz byte [ebp]
 	ret
 
 defword '<', 1, word_lt, word_not
 	pspop eax
 	sub [ebp], eax
-	jmp set_PS_to_carry
+	mov dword [ebp], 0
+	setc byte [ebp]
+	ret
 
 defword '<<c', 3, word_shlc, word_lt
-	sub ebp,4
+	pspush 0
 	shl dword [ebp+4], 1
-	jmp set_PS_to_carry
+	setc byte [ebp]
+	ret
 
 defword '>>c', 3, word_shrc, word_shlc
-	sub ebp,4
+	pspush 0
 	shr dword [ebp+4], 1
-	jmp set_PS_to_carry
+	setc byte [ebp]
+	ret
 
 ; ( n u -- n )
 defword 'lshift', 6, word_lshift, word_shrc