[llvm-bugs] [Bug 39159] New: [llvm-exegesis] Instructions should avoid tied registers (BLENDVPD/BLENDVPS/PBLENDVB etc.)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39159

            Bug ID: 39159
           Summary: [llvm-exegesis] Instructions should avoid tied
                    registers (BLENDVPD/BLENDVPS/PBLENDVB etc.)
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: andrea.dibiagio at gmail.com, clement.courbet at gmail.com,
                    gchatelet at google.com, llvm-bugs at lists.llvm.org

BLENDVPD/BLENDVPS/PBLENDVB use xmm0 as the mask src register, but
llvm-exegesis's uop computation uses this register both as a src and dst,
resulting in spurious results (extra uop counts, stalls etc.)

mode:            uops
key:             
  instructions:    
    - 'BLENDVPDrm0 XMM0 XMM0 RDI i_0x1x  i_0x0x '
    - 'BLENDVPDrm0 XMM1 XMM1 RDI i_0x1x  i_0x64x '
    - 'BLENDVPDrm0 XMM2 XMM2 RDI i_0x1x  i_0x128x '
    - 'BLENDVPDrm0 XMM3 XMM3 RDI i_0x1x  i_0x192x '
    - 'BLENDVPDrm0 XMM4 XMM4 RDI i_0x1x  i_0x256x '
    - 'BLENDVPDrm0 XMM5 XMM5 RDI i_0x1x  i_0x320x '
    - 'BLENDVPDrm0 XMM6 XMM6 RDI i_0x1x  i_0x384x '
    - 'BLENDVPDrm0 XMM7 XMM7 RDI i_0x1x  i_0x448x '
    - 'BLENDVPDrm0 XMM8 XMM8 RDI i_0x1x  i_0x512x '
    - 'BLENDVPDrm0 XMM9 XMM9 RDI i_0x1x  i_0x576x '
    - 'BLENDVPDrm0 XMM10 XMM10 RDI i_0x1x  i_0x640x '
    - 'BLENDVPDrm0 XMM11 XMM11 RDI i_0x1x  i_0x704x '
    - 'BLENDVPDrm0 XMM12 XMM12 RDI i_0x1x  i_0x768x '
    - 'BLENDVPDrm0 XMM13 XMM13 RDI i_0x1x  i_0x832x '
    - 'BLENDVPDrm0 XMM14 XMM14 RDI i_0x1x  i_0x896x '
    - 'BLENDVPDrm0 XMM15 XMM15 RDI i_0x1x  i_0x960x '
  config:          ''
  register_initial_values: 
    - 'XMM0=0x0'
    - 'XMM1=0x0'
    - 'XMM2=0x0'
    - 'XMM3=0x0'
    - 'XMM4=0x0'
    - 'XMM5=0x0'
    - 'XMM6=0x0'
    - 'XMM7=0x0'
    - 'XMM8=0x0'
    - 'XMM9=0x0'
    - 'XMM10=0x0'
    - 'XMM11=0x0'
    - 'XMM12=0x0'
    - 'XMM13=0x0'
    - 'XMM14=0x0'
    - 'XMM15=0x0'
cpu_name:        btver2
llvm_triple:     x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:    
  - { debug_string: JFPU0, value: 1.47, per_snippet_value: 23.52, key: JFPU0 }
  - { debug_string: JFPU1, value: 1.5349, per_snippet_value: 24.5584, key:
JFPU1 }
  - { debug_string: NumMicroOps, value: 4.0158, per_snippet_value: 64.2528, 
      key: NumMicroOps }

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