[llvm-bugs] [Bug 31345] New: Optimize 16-bit ANDs with '1'

via llvm-bugs llvm-bugs at lists.llvm.org
Sat Dec 10 20:48:36 PST 2016


            Bug ID: 31345
           Summary: Optimize 16-bit ANDs with '1'
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: AVR
          Assignee: unassignedbugs at nondot.org
          Reporter: dylanmckay34 at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Currently if we get an AND with immediate '0xff00', we will emit two ANDI
instructions, one to AND with '0xff' and one to AND with '0x00'.

ANDing with 255 is unnecessary and it just causes an extra redundant operation.

Let's optimise this operation in the pseudo instruction expander.

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