llvm dev - Jan 2016 - Diff to add ARMv6L to Target parser

Hi all.

I’ve been working with Swift on ARMv6 and v7.  While working with ARMv6 on
linux, I noticed that my arm architecture canonicalization code didn’t produce
the expected result.  The code that I had been using (within Swift’s Driver.cpp
the following:

static llvm::Triple computeTargetTriple(StringRef DefaultTargetTriple) {
  llvm::Triple triple = llvm::Triple(DefaultTargetTriple);

  // Canonicalization of all armv6 sub architectures to armv6
  if (triple.getArch() == llvm::Triple::ArchType::arm) {
    if (triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6  ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6m ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6k ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6t2) {
      triple.setArchName("armv6");
    }
  }

  // Canonicalization of all armv7 sub architectures to armv7
  if (triple.getArch() == llvm::Triple::ArchType::arm) {
    if (triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7   ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7em ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7m  ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7s  ||
        triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7k) {
      triple.setArchName("armv7");
    }
  }

  return triple;
}
However, because the DefaultTargetTriple is armv6l-unknown-linux-gnueabihf, and
llvm didn’t know about v6l, it would fail to match and canonicalize to armv6.  I
added the notion of v6l to llvm to address this.

Thoughts/comments?
- Will

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On 3 January 2016 at 22:28, William Dillon via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> However, because the DefaultTargetTriple is armv6l-unknown-linux-gnueabihf,
and llvm didn’t know about v6l, it would fail to match and canonicalize to
armv6.  I added the notion of v6l to llvm to address this.
Hi Will,

ARMv6l was definitely there once. I'm not sure what happened.

I'm copying the ARM folks that did most of the recent changes in hope
they can shed some light.

cheers,
--renato

>> However, because the DefaultTargetTriple is
armv6l-unknown-linux-gnueabihf,
>> and llvm didn’t know about v6l, it would fail to match and canonicalize
to armv6.
>>  I added the notion of v6l to llvm to address this.
>
> ARMv6l was definitely there once. I'm not sure what happened.
>
> I'm copying the ARM folks that did most of the recent changes in hope
they can
> shed some light.
Going back through SVN history, I cannot find any evidence that ARMv6L ever
existed.

There used to be ARMv6HL, until r252903 changed it from an architecture variant
into an alias for ARMv6K; i.e. ARMv6HL can still be used in a target triple.

For a reference,
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/TargetParser.cpp?revision=238651
is the last version of TargetParser before any of our changes, i.e. authored
purely by Renato.
One can see it has v6HL but not v6L.