[llvm] r323371 - [AArch64][GlobalISel] Fall back during AArch64 isel if we have a volatile load.

[Hans Wennborg via llvm-commits]

Sure, r323523.

On Thu, Jan 25, 2018 at 5:59 PM, Amara Emerson <aemerson at apple.com> wrote:

> > On 25 Jan 2018, at 15:29, Hans Wennborg <hans at chromium.org> wrote:
> >
> > OK, merged them in r323434.
> >
> > On Wed, Jan 24, 2018 at 10:02 PM, Amara Emerson <aemerson at apple.com>
> wrote:
> >>> On 24 Jan 2018, at 20:35, Amara Emerson via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
> >>>
> >>> Author: aemerson
> >>> Date: Wed Jan 24 12:35:37 2018
> >>> New Revision: 323371
> >>>
> >>> URL: http://llvm.org/viewvc/llvm-project?rev=323371&view=rev
> >>> Log:
> >>> [AArch64][GlobalISel] Fall back during AArch64 isel if we have a
> volatile load.
> >>>
> >>> The tablegen imported patterns for sext(load(a)) don't check for
> single uses
> >>> of the load or delete the original after matching. As a result two
> loads are
> >>> left in the generated code. This particular issue will be fixed by
> adding
> >>> support for a G_SEXTLOAD opcode in future.
> >>>
> >>> There are however other potential issues around this that wouldn't be
> fixed by
> >>> a G_SEXTLOAD, so until we have a proper solution we don't try to
> handle volatile
> >>> loads at all in the AArch64 selector.
> >>>
> >>> Fixes/works around PR36018.
> >>>
> >>> Added:
> >>>   llvm/trunk/test/CodeGen/AArch64/GlobalISel/
> irtranslator-volatile-load-pr36018.ll
> >>> Modified:
> >>>   llvm/trunk/lib/Target/AArch64/AArch64InstructionSelector.cpp
> >>>
> >>> Modified: llvm/trunk/lib/Target/AArch64/AArch64InstructionSelector.cpp
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/
> AArch64/AArch64InstructionSelector.cpp?rev=323371&r1=323370&r2=
> 323371&view=diff
> >>> ============================================================
> ==================
> >>> --- llvm/trunk/lib/Target/AArch64/AArch64InstructionSelector.cpp
> (original)
> >>> +++ llvm/trunk/lib/Target/AArch64/AArch64InstructionSelector.cpp Wed
> Jan 24 12:35:37 2018
> >>> @@ -931,6 +931,12 @@ bool AArch64InstructionSelector::select(
> >>>      return false;
> >>>    }
> >>>
> >>> +    // FIXME: PR36018: Volatile loads in some cases are incorrectly
> selected by
> >>> +    // folding with an extend. Until we have a G_SEXTLOAD solution
> bail out if
> >>> +    // we hit one.
> >>> +    if (Opcode == TargetOpcode::G_LOAD && MemOp.isVolatile())
> >>> +      return false;
> >>> +
> >>>    const unsigned PtrReg = I.getOperand(1).getReg();
> >>> #ifndef NDEBUG
> >>>    const RegisterBank &PtrRB = *RBI.getRegBank(PtrReg, MRI, TRI);
> >>>
> >>> Added: llvm/trunk/test/CodeGen/AArch64/GlobalISel/
> irtranslator-volatile-load-pr36018.ll
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> CodeGen/AArch64/GlobalISel/irtranslator-volatile-load-
> pr36018.ll?rev=323371&view=auto
> >>> ============================================================
> ==================
> >>> --- llvm/trunk/test/CodeGen/AArch64/GlobalISel/
> irtranslator-volatile-load-pr36018.ll (added)
> >>> +++ llvm/trunk/test/CodeGen/AArch64/GlobalISel/
> irtranslator-volatile-load-pr36018.ll Wed Jan 24 12:35:37 2018
> >>> @@ -0,0 +1,14 @@
> >>> +; RUN: llc -O0 -mtriple=aarch64-apple-ios -o - %s | FileCheck %s
> >>> +
> >>> + at g = global i16 0, align 2
> >>> +declare void @bar(i32)
> >>> +
> >>> +; Check that only one load is generated. We fall back to
> >>> +define hidden void @foo() {
> >>> +; CHECK-NOT: ldrh
> >>> +; CHECK: ldrsh
> >>> +  %1 = load volatile i16, i16* @g, align 2
> >>> +  %2 = sext i16 %1 to i32
> >>> +  call void @bar(i32 %2)
> >>> +  ret void
> >>> +}
> >>>
> >>>
> >>> _______________________________________________
> >>> llvm-commits mailing list
> >>> llvm-commits at lists.llvm.org
> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
> >>
> >> Hi Hans,
> >>
> >> This is a 6.0 blocker, can we have r323369 and this commit on the 6.0
> branch please?
> >>
> >> Thanks,
> >> Amara
>
> Could we also have r323384? It’s just a tweak to a test to skip on
> non-asserts builds.
>
> Thanks,
> Amara
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180126/01d7d878/attachment.html>