BSR (R64, M64) - Latency

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
  

• Show nanoBench command
• Results:
  • Instructions retired: 1.0
  • Core cycles: 1.01
  • Reference cycles: 0.96
  • RS_UOPS_DISPATCHED: 3.0

Experiment 2

• Instruction: BSR R8, qword ptr [R14]
• Chain instructions: MOVSX R8, R8D;MOVSX R8, R8D;MOVSX R8, R8D;MOVSX R8, R8D;MOVSX R8, R8D
• Chain latency: 5
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 63 c0             	movsxd r8,r8d
     7:	4d 63 c0             	movsxd r8,r8d
     a:	4d 63 c0             	movsxd r8,r8d
     d:	4d 63 c0             	movsxd r8,r8d
    10:	4d 63 c0             	movsxd r8,r8d
  

• Show nanoBench command
• Results:
  • Instructions retired: 6.0
  • Core cycles: 6.15
  • Reference cycles: 6.14
  • RS_UOPS_DISPATCHED: 8.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Chain instructions: CMOVZ R15, R15;MOVSX R8, R15D;MOVSX R8, R8D;MOVSX R8, R8D;MOVSX R8, R8D;MOVSX R8, R8D
• Chain latency: 7
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 0f 44 ff          	cmove  r15,r15
     8:	4d 63 c7             	movsxd r8,r15d
     b:	4d 63 c0             	movsxd r8,r8d
     e:	4d 63 c0             	movsxd r8,r8d
    11:	4d 63 c0             	movsxd r8,r8d
    14:	4d 63 c0             	movsxd r8,r8d
  

• Show nanoBench command
• Results:
  • Instructions retired: 7.0
  • Core cycles: 4.29
  • Reference cycles: 4.29
  • RS_UOPS_DISPATCHED: 10.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Chain instructions: MOVSX R8, R8D;XOR R14, R8;XOR R14, R8;XOR R14, R8;XOR R14, R8
• Chain latency: 5
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 63 c0             	movsxd r8,r8d
     7:	4d 31 c6             	xor    r14,r8
     a:	4d 31 c6             	xor    r14,r8
     d:	4d 31 c6             	xor    r14,r8
    10:	4d 31 c6             	xor    r14,r8
  

• Show nanoBench command
• Results:
  • Instructions retired: 6.0
  • Core cycles: 10.38
  • Reference cycles: 10.38
  • RS_UOPS_DISPATCHED: 8.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14+R13]
• Chain instructions: MOVSX R8, R8D;XOR R13, R8;XOR R13, R8;XOR R13, R8;XOR R13, R8
• Chain latency: 5
• Code:

     0:	4f 0f bd 04 2e       	bsr    r8,QWORD PTR [r14+r13*1]
     5:	4d 63 c0             	movsxd r8,r8d
     8:	4d 31 c5             	xor    r13,r8
     b:	4d 31 c5             	xor    r13,r8
     e:	4d 31 c5             	xor    r13,r8
    11:	4d 31 c5             	xor    r13,r8
  

• Init:

  XOR R13, R13

• Show nanoBench command
• Results:
  • Instructions retired: 6.0
  • Core cycles: 10.38
  • Reference cycles: 10.37
  • RS_UOPS_DISPATCHED: 8.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Chain instructions: MOVSX R12, R8D;MOVSX R12, R12d;MOVSX R12, R12d;MOVSX R12, R12d;mov [R14], R12
• Chain latency: ≥5
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 63 e0             	movsxd r12,r8d
     7:	4d 63 e4             	movsxd r12,r12d
     a:	4d 63 e4             	movsxd r12,r12d
     d:	4d 63 e4             	movsxd r12,r12d
    10:	4d 89 26             	mov    QWORD PTR [r14],r12
  

• Show nanoBench command
• Results:
  • Instructions retired: 6.0
  • Core cycles: 11.06
  • Reference cycles: 11.09
  • RS_UOPS_DISPATCHED: 9.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Chain instruction: CMOVZ R14, R14
• Chain latency: 2
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 0f 44 f6          	cmove  r14,r14
  

• Show nanoBench command
• Results:
  • Instructions retired: 2.0
  • Core cycles: 6.68
  • Reference cycles: 6.66
  • RS_UOPS_DISPATCHED: 5.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14+R13]
• Chain instruction: CMOVZ R13, R13
• Chain latency: 2
• Code:

     0:	4f 0f bd 04 2e       	bsr    r8,QWORD PTR [r14+r13*1]
     5:	4d 0f 44 ed          	cmove  r13,r13
  

• Init:

  XOR R13, R13

• Show nanoBench command
• Results:
  • Instructions retired: 2.0
  • Core cycles: 6.68
  • Reference cycles: 6.66
  • RS_UOPS_DISPATCHED: 5.0

Experiment 1

• Instruction: BSR R8, qword ptr [R14]
• Chain instructions: CMOVZ R12, R12;MOVSX R12, R12d;MOVSX R12, R12d;MOVSX R12, R12d;MOVSX R12, R12d;mov [R14], R12
• Chain latency: ≥7
• Code:

     0:	4d 0f bd 06          	bsr    r8,QWORD PTR [r14]
     4:	4d 0f 44 e4          	cmove  r12,r12
     8:	4d 63 e4             	movsxd r12,r12d
     b:	4d 63 e4             	movsxd r12,r12d
     e:	4d 63 e4             	movsxd r12,r12d
    11:	4d 63 e4             	movsxd r12,r12d
    14:	4d 89 26             	mov    QWORD PTR [r14],r12
  

• Show nanoBench command
• Results:
  • Instructions retired: 7.0
  • Core cycles: 13.0
  • Reference cycles: 13.02
  • RS_UOPS_DISPATCHED: 11.0