[llvm-bugs] [Bug 39721] New: [AArch64] print "uxtl" simplified mnemonic asm

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Nov 20 08:19:13 PST 2018


            Bug ID: 39721
           Summary: [AArch64] print "uxtl" simplified mnemonic asm
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: spatel+llvm at rotateright.com
                CC: arnaud.degrandmaison at arm.com,
                    llvm-bugs at lists.llvm.org, peter.smith at linaro.org,
                    Ties.Stuij at arm.com

As noted in https://reviews.llvm.org/D54392 :

define <8 x i16> @uxtl(<8 x i8> %a) {
  %r = zext <8 x i8> %a to <8 x i16>
  ret <8 x i16> %r

$ llc -o - uxtl.ll -mtriple=aarch64
        ushll   v0.8h, v0.8b, #0

The ARM ARM says:
"UXTL{2} <Vd>.<Ta>, <Vn>.<Tb>
is equivalent to
USHLL{2} <Vd>.<Ta>, <Vn>.<Tb>, #0
and is the preferred disassembly..."

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