Bryand and O'Hallaron
                             Chapter 3 Section 3.6.2
                            Condition Code Instructions


1. Compare and Test Instructions 

Instruction         Effect                     Description

cmpb  s2,s1         s1-s2                      Compare bytes
testb s2,s1         s1&s2                      Test byte

cmpw  s2,s1         s1-s2                      Compare words
testw s2,s1         s1&s2                      Test word

cmpl  s2,s1         s1-s2                      Compare double words
testl s2,s1         s1&s2                      Test double words

2. The test instructions set the zero and negative flags based on the
   bitwise and of the two operations. The instruction

      testl  %eax,%eax
	
   will set the zero and negative bits based on the value in %eax.


3. Figure 3.10 The Set Instructions (byte destination only)

Instruction  Synonym     Effect                Description

sete  D      setz        D <- ZF               Equal/Zero
setne D      setnz       D <- ~ZF              Not equal/Not zero

sets  D                  D <- SF               Negative
setns D                  D <- ~SF              Nonnegative

setg  D      setnle      D <- ~(SF^OF)&~ZF     Greater (signed >)
setge D      setnl       D <- ~(SF^OF)         Greater or equal (signed >=)
setl  D      setnge      D <-  (SF^OF)         Less (signed <)
setle D      setng       D <-  (SF^OF)&~ZF     Less or equal (signed <=)

seta  D      setnbe      D <- ~(SF^OF)&~ZF     Greater (signed >)
setae D      setnb       D <- ~(SF^OF)         Greater or equal (signed >=)
setb  D      setnae      D <-  (SF^OF)         Less (signed <)
setbe D      setna       D <-  (SF^OF)&~ZF     Less or equal (signed <=)


4. Typical instruction sequence for a C predicate such as (a < b)

   #assumes a is in %edx, b is in %eax

      cmpl   %eax,%edx       # compute %edx - %eax (thats a - b)
      setl   %al             # low order byte = SF^0F (1 if a < b signed)
      movzbl %al,%eax        # upper 24 bits of %eax set to zero

   When a "cmpl b,a" instruction is followed by "setl", we need to
   read the combination as "cmpl b>a". The "less" refers to the second
   operand of the cmpl. Very confusing (and the result of the assembler
   using AT&T syntax rather than Intel syntax). 


5. Practice Problem 3.7 on page 151