LOOPNE (Rel8) - Latency

Experiment 1

• Instruction: LOOPNE 1f; 1:
• Code:

     0:	e0 00                	loopne 0x2
  

• Show nanoBench command
• Results:
  • Instructions retired: 1.0
  • Core cycles: 10.0
  • Reference cycles: 4.98
  • UOPS_RETIRED.ALL: 8.0

Experiment 2

• Instruction: LOOPNE 1f; 1:
• Chain instructions: MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX
• Chain latency: 17
• Code:

     0:	e0 00                	loopne 0x2
     2:	48 63 c9             	movsxd rcx,ecx
     5:	48 63 c9             	movsxd rcx,ecx
     8:	48 63 c9             	movsxd rcx,ecx
     b:	48 63 c9             	movsxd rcx,ecx
     e:	48 63 c9             	movsxd rcx,ecx
    11:	48 63 c9             	movsxd rcx,ecx
    14:	48 63 c9             	movsxd rcx,ecx
    17:	48 63 c9             	movsxd rcx,ecx
    1a:	48 63 c9             	movsxd rcx,ecx
    1d:	48 63 c9             	movsxd rcx,ecx
    20:	48 63 c9             	movsxd rcx,ecx
    23:	48 63 c9             	movsxd rcx,ecx
    26:	48 63 c9             	movsxd rcx,ecx
    29:	48 63 c9             	movsxd rcx,ecx
    2c:	48 63 c9             	movsxd rcx,ecx
    2f:	48 63 c9             	movsxd rcx,ecx
    32:	48 63 c9             	movsxd rcx,ecx
  

• Show nanoBench command
• Results:
  • Instructions retired: 18.0
  • Core cycles: 21.0
  • Reference cycles: 10.47
  • UOPS_RETIRED.ALL: 25.0

Experiment 1

• Instruction: LOOPNE 1f; 1:
• Chain instructions: MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;MOVSX RCX, ECX;TEST RCX, RCX
• Chain latency: 17
• Code:

     0:	e0 00                	loopne 0x2
     2:	48 63 c9             	movsxd rcx,ecx
     5:	48 63 c9             	movsxd rcx,ecx
     8:	48 63 c9             	movsxd rcx,ecx
     b:	48 63 c9             	movsxd rcx,ecx
     e:	48 63 c9             	movsxd rcx,ecx
    11:	48 63 c9             	movsxd rcx,ecx
    14:	48 63 c9             	movsxd rcx,ecx
    17:	48 63 c9             	movsxd rcx,ecx
    1a:	48 63 c9             	movsxd rcx,ecx
    1d:	48 63 c9             	movsxd rcx,ecx
    20:	48 63 c9             	movsxd rcx,ecx
    23:	48 63 c9             	movsxd rcx,ecx
    26:	48 63 c9             	movsxd rcx,ecx
    29:	48 63 c9             	movsxd rcx,ecx
    2c:	48 63 c9             	movsxd rcx,ecx
    2f:	48 63 c9             	movsxd rcx,ecx
    32:	48 85 c9             	test   rcx,rcx
  

• Show nanoBench command
• Results:
  • Instructions retired: 18.0
  • Core cycles: 21.0
  • Reference cycles: 10.44
  • UOPS_RETIRED.ALL: 25.0

Experiment 2

• Instruction: LOOPNE 1f; 1:
• Chain instruction: TEST RCX, RCX
• Chain latency: 1
• Code:

     0:	e0 00                	loopne 0x2
     2:	48 85 c9             	test   rcx,rcx
  

• Show nanoBench command
• Results:
  • Instructions retired: 2.0
  • Core cycles: 13.0
  • Reference cycles: 6.5
  • UOPS_RETIRED.ALL: 9.0

Experiment 3 (with dependency-breaking instructions)

• Instruction: LOOPNE 1f; 1:
• Chain instructions: TEST RCX, RCX;;MOV RCX, 0
• Chain latency: 1
• Code:

     0:	e0 00                	loopne 0x2
     2:	48 85 c9             	test   rcx,rcx
     5:	48 c7 c1 00 00 00 00 	mov    rcx,0x0
  

• Show nanoBench command
• Results:
  • Instructions retired: 3.0
  • Core cycles: 11.0
  • Reference cycles: 5.48
  • UOPS_RETIRED.ALL: 10.0