[llvm-bugs] [Bug 42228] New: [llvm-exegesis] fails to measure scalar division instructions

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Jun 11 03:00:42 PDT 2019


            Bug ID: 42228
           Summary: [llvm-exegesis] fails to measure scalar division
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: llvm-exegesis
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: clement.courbet at gmail.com, gchatelet at google.com,
                    llvm-bugs at lists.llvm.org

$ ./bin/llvm-exegesis -mode=latency --opcode-name=DIV8r
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-d9586f.o
mode:            latency
    - 'DIV8r R15B'
  config:          ''
    - 'R15B=0x0'
    - 'AX=0x0'
cpu_name:        bdver2
llvm_triple:     x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:    []
error:           snippet crashed while running
info:            Repeating a single implicitly serial instruction

$ /usr/bin/objdump -d /tmp/snippet-d9586f.o

/tmp/snippet-d9586f.o:     file format elf64-x86-64

Disassembly of section .text:

0000000000000000 <foo>:
       0:       41 57                   push   %r15
       2:       41 b7 00                mov    $0x0,%r15b
       5:       66 b8 00 00             mov    $0x0,%ax
       9:       41 f6 f7                div    %r15b
       c:       41 f6 f7                div    %r15b
       f:       41 f6 f7                div    %r15b
      12:       41 f6 f7                div    %r15b

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