[llvm-bugs] [Bug 36881] New: [X86] TZCNT/LZCNT/BSR/BSF have weird SchedRW

via llvm-bugs llvm-bugs at lists.llvm.org
Fri Mar 23 11:11:51 PDT 2018


            Bug ID: 36881
           Summary: [X86] TZCNT/LZCNT/BSR/BSF have weird SchedRW
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: craig.topper at gmail.com
                CC: llvm-bugs at lists.llvm.org

BSR and BSF are using WriteShift. TZCNT/LZCNT are using WriteIMul.

I assume that generally WriteShift would be faster than WriteIMul. But
TZCNT/LZCNT are know to be better than BSR/BSF on some CPUs.

You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180323/af3b2c33/attachment-0001.html>

More information about the llvm-bugs mailing list