From: Luke Lau <luke_lau@icloud.com>
Date: Mon, 29 Jul 2019 23:48:00 +0000 (+0100)
Subject: Fix = codegen
X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=6cad928374127b2fae65d7023fd31a725f4bd1d9

Fix = codegen

Use the sete instruction instead of the just plain wrong subtraction
method
---

diff --git a/codegen.scm b/codegen.scm
index 00e0129..c736773 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -46,9 +46,9 @@
   (codegen-expr a si env)
   (emit "movq %rax, ~a(%rbp)" si)
   (codegen-expr b (- si wordsize) env)
-  (emit "subq ~a(%rbp), %rax" si)
-  (emit "not %rax")
-  (emit "andq $1, %rax"))
+  (emit "## ~a = ~b" a b)
+  (emit "cmpq ~a(%rbp), %rax" si)
+  (emit "sete %al"))
 
 					; 'write file handle addr-string num-bytes