Amd Athlon Processor Specific Code; Blended Amd-K6 And Amd Athlon Processor Code - AMD Athlon Processor x86 Optimization Manual

AMD Athlon™ Processor x86 Code Optimization
AMD Athlon™ Processor Specific Code
Blended AMD-K6
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Example 1 — Signed integer ABS function (X = labs(X)):
MOV ECX, [X]
MOV EBX, ECX
NEG ECX
CMOVS ECX, EBX
MOV [X], ECX
Example 2 — Unsigned integer min function (z = x < y ? x : y):
MOV EAX, [X]
MOV EBX, [Y]
CMP EAX, EBX
CMOVNC EAX, EBX
MOV [Z], EAX
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and AMD Athlon™ Processor Code
Example 3 — Signed integer ABS function (X = labs(X)):
MOV ECX, [X]
MOV EBX, ECX
SAR ECX, 31
XOR EBX, ECX
SUB EBX, ECX
MOV [X], EBX
Example 4 — Unsigned integer min function (z = x < y ? x : y):
MOV EAX, [x]
MOV EBX, [y]
SUB EAX, EBX
SBB ECX, ECX
AND ECX, EAX
ADD ECX, EBX
MOV [z], ECX
Example 5 — Hexadecimal to ASCII conversion
(y=x < 10 ? x + 0x30: x + 0x41):
MOV AL, [X]
CMP AL, 10
SBB AL, 69h
DAS
MOV [Y],AL
;load value
;save value
;–value
;if –value is negative, select value
;save labs result
;load X value
;load Y value
;EBX<=EAX ? CF=0 : CF=1
;EAX=(EBX<=EAX) ? EBX:EAX
;save min (X,Y)
;load value
;save value
;x < 0 ? 0xffffffff : 0
;x < 0 ? ~x : x
;x < 0 ? (~x)+1 : x
;x < 0 ? -x : x
;load x
;load y
;x < y ? CF : NC ; x - y
;x < y ? 0xffffffff : 0
;x < y ? x - y : 0
;x < y ? x - y + y : y
;x < y ? x : y
;load X value
;if x is less than 10, set carry flag
;0..9 –> 96h, Ah..Fh –> A1h...A6h
;0..9: subtract 66h, Ah..Fh: Sub. 60h
;save conversion in y
Avoid Branches Dependent on Random Data
22007E/0—November 1999