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-rw-r--r--amd64.e10
1 files changed, 10 insertions, 0 deletions
diff --git a/amd64.e b/amd64.e
index 4ffc64f..e098505 100644
--- a/amd64.e
+++ b/amd64.e
@@ -851,11 +851,21 @@ s" :cc-greater" keyword
 ~ Control flow instructions
 ~ ~~~~~~~~~~~~~~~~~~~~~~~~~
 
+~   Pretend to subtract right from left, and set the flags the same way as if
+~ we actually had.
+~
 ~ (output point, left register, right register -- output point)
 : cmp-reg64-reg64
   3roll rex-w 0x3B pack8 3unroll
   reg64 swap addressing-reg64 ;
 
+~   Pretend to xor left with right, and set the flags the same way as if we
+~ actually had.
+~
+~   The names of the condition codes can be a little confusing when using them
+~ after "test", because they're really premised on the idea that you did
+~ "cmp".
+~
 ~ (output point, left register, right register -- output point)
 : test-reg64-reg64
   3roll rex-w 0x85 pack8 3unroll