[llvm-dev] [Hexagon] Type Legalization
Craig Topper via llvm-dev
llvm-dev at lists.llvm.org
Thu Sep 21 22:19:05 PDT 2017
Is VT a legal type on Hexagon? It looks like Hexagon may be setting SHL as
Custom for every defined vector type. Try adding TLI.isTypeLegal(VT) too.
~Craig
On Thu, Sep 21, 2017 at 10:06 PM, Haidl, Michael <
michael.haidl at uni-muenster.de> wrote:
> Hi Sanjay,
>
> thanks for this information. I did get a little bit further with the
> patch. However, Hexagon gives me headaches.
>
> I tried to limit the scope of the patch to the BeforeLegalizeTypes phase
> and Hexagon still reaches the unreachable. Hexagon tries to split or
> widen a vector type for a node with custom lowering where the
> unreachable arises from inside TargetLowering::ReplaceNodeResults which
> is not overwritten in the Hexagon backend.
>
> To avoid generating illegal code after all I queried TLI if all
> generated operations are legal operations for the given vector type.
>
> if ( TLI.isOperationLegal(ISD::SUB, VT)
> && TLI.isOperationLegal(ISD::ADD, VT)
> && TLI.isOperationLegal(ISD::SHL, VT)
> && TLI.isOperationLegal(ISD::SRA, VT)) {
>
> The Hexagon backend says happily: yes! Go ahead!
> When it comes to HexagonDAGToDAGISel and the type should be legalized no
> custom lowering is found and TargetLowering::ReplaceNodeResults is
> called which falls back to the default implementation and the
> unreachable is trigged.
>
> Is this really working as intended or am I missing something here?
>
> Cheers,
> Michael
>
> On 20.09.2017 16:10, Sanjay Patel wrote:
> > There are multiple problems/questions here:
> >
> > 1. Make sure you've updated trunk to the latest rev before running
> > update_llc_test_checks.py on lea-3.ll. Ie, I would only expect the
> > output you're seeing if you're running the script on a version of that
> > test file before r313631. After that commit, each RUN has its own check
> > prefix, so there should be no conflict opportunity.
> >
> > 2. I didn't realize the scope of the patch covered all targets and both
> > scalars and vectors. That isn't going to work as-is. We can't assume
> > that every target and data type will prefer to replace that multiply.
> > Even the x86 diffs in lea-3.ll are regressions:
> >
> > -; LNX1-NEXT: leal (%rdi,%rdi,2), %eax
> > +; LNX1-NEXT: leal (,%rdi,4), %eax
> > +; LNX1-NEXT: subl %edi, %eax
> >
> > I suggest taking a smaller first step by limiting the patch to cases
> > where the multiply is not a legal op for a target
> (TLI.isOperationLegal()).
> >
> > 3. Since the patch can cause a crash, that needs to be investigated
> > first. I didn't look into it, but my guess for the Hexagon crash (and
> > probably other targets) is that you're trying to create illegal
> > ops after the DAG has been legalized. So that's another potential way to
> > limit the scope of the patch - don't try the transform unless we're
> > pre-legalization:
> > if (Level < AfterLegalizeDAG) { // do something }
> >
> >
> >
> > On Wed, Sep 20, 2017 at 4:17 AM, Haidl, Michael
> > <michael.haidl at uni-muenster.de <mailto:michael.haidl at uni-muenster.de>>
> > wrote:
> >
> > Hi,
> >
> > I am currently working on a more or less intrusive patch (D37896),
> which
> > pulls optimizations on multiplications from some back-ends, e.g.,
> (mul
> > x, 2^N + 1) => (add (shl x, N), x) in AArch64, into the DAGCombiner
> to
> > have this optimization generic on all targets.
> > However, running the LLVM Tests leads to 67 unexpected results.
> >
> > Am 19.09.2017 um 15:58 schrieb Sanjay Patel:
> > > For the tests that are changing, you should see if those changes
> are
> > > improvements, regressions, or neutral. This is unfortunately not
> > always
> > > obvious for x86 asm, so feel free to just post those diffs in an
> > updated
> > > version of the patch at D37896.
> > >
> > > If the test files have auto-generated assertions (look for this
> > string
> > > on the first line of the test file: "NOTE: Assertions have been
> > > autogenerated by utils/update_llc_test_checks.py"...
> > > and both of these do as of: https://reviews.llvm.org/rL313631
> > <https://reviews.llvm.org/rL313631>
> > > <https://reviews.llvm.org/rL313631
> > <https://reviews.llvm.org/rL313631>> ), then it's easy to observe
> the
> > > diffs by re-running that script after your code patch is applied:
> > > $ /path/to/update_llc_test_checks.py
> --llc=/path/to/local/and/new/llc
> > > lea-3.ll
> > > $ svn diff lea-3.ll
> >
> > As described by Sanjay in the original thread, I updated the llc
> tests
> > but some of the tests were not updated.
> >
> > For example: CodeGen/X86/lea-3.ll produces the following output:
> > llvm/utils/update_llc_test_checks.py --llc=/home/dev/local/bin/llc
> > CodeGen/X86/lea-3.ll
> > WARNING: Found conflicting asm under the same prefix: 'CHECK'!
> > WARNING: Found conflicting asm under the same prefix: 'CHECK'!
> > WARNING: Found conflicting asm under the same prefix: 'CHECK'!
> >
> > leaving parts of the test unchanged and the tests still fail.
> >
> > Other tests like CodeGen/AArch64/aarch64-gep-opt.ll results in:
> > WARNING: Skipping non-FileChecked RUN line: llc -O3
> > -aarch64-enable-gep-opt=true -mattr=-use-aa
> -print-after=codegenprepare
> > < %s >%t 2>&1 && FileCheck --check-prefix=CHECK-NoAA <%t %s
> > WARNING: Skipping non-FileChecked RUN line: llc -O3
> > -aarch64-enable-gep-opt=true -mattr=+use-aa
> -print-after=codegenprepare
> > < %s >%t 2>&1 && FileCheck --check-prefix=CHECK-UseAA <%t %s
> > WARNING: Skipping non-FileChecked RUN line: llc -O3
> > -aarch64-enable-gep-opt=true -print-after=codegenprepare
> -mcpu=cyclone <
> > %s >%t 2>&1 && FileCheck --check-prefix=CHECK-NoAA <%t %s
> > WARNING: Skipping non-FileChecked RUN line: llc -O3
> > -aarch64-enable-gep-opt=true -print-after=codegenprepare
> > -mcpu=cortex-a53 < %s >%t 2>&1 && FileCheck
> --check-prefix=CHECK-UseAA
> > <%t %s
> >
> > And the worst thing I witnessed was with the Hexagon back-end were my
> > changes in DAGCombiner trigger an Unreachable:
> >
> > home/dev/llvm/build/./bin/llc -march=hexagon -mcpu=hexagonv5
> > -disable-hsdr <
> > /home/dev/llvm/llvm/test/CodeGen/Hexagon/vect/vect-cst-v4i32.ll |
> > /home/dev/llvm/build/./bin/FileCheck
> > /home/dev/llvm/llvm/test/CodeGen/Hexagon/vect/vect-cst-v4i32.ll
> > --
> > Exit Code: 2
> >
> > Command Output (stderr):
> > --
> > ReplaceNodeResults not implemented for this target!
> > UNREACHABLE executed at
> > /home/dev/llvm/llvm/include/llvm/Target/TargetLowering.h:3164!
> > #0 0x00007f1b2d330cfa llvm::sys::PrintStackTrace(llvm::raw_ostream&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMSupport.so.6+0x116cfa)
> > #1 0x00007f1b2d32ea9e llvm::sys::RunSignalHandlers()
> > (/home/dev/llvm/build/bin/../lib/libLLVMSupport.so.6+0x114a9e)
> > #2 0x00007f1b2d32ec04 SignalHandler(int)
> > (/home/dev/llvm/build/bin/../lib/libLLVMSupport.so.6+0x114c04)
> > #3 0x00007f1b2c3ed7f0 (/lib/x86_64-linux-gnu/libc.so.6+0x357f0)
> > #4 0x00007f1b2c3ed77f gsignal (/lib/x86_64-linux-gnu/libc.
> so.6+0x3577f)
> > #5 0x00007f1b2c3ef37a abort (/lib/x86_64-linux-gnu/libc.
> so.6+0x3737a)
> > #6 0x00007f1b2d2b012a
> > (/home/dev/llvm/build/bin/../lib/libLLVMSupport.so.6+0x9612a)
> > #7 0x00007f1b359326ec
> > (/home/dev/llvm/build/bin/../lib/libLLVMHexagonCodeGen.so.
> 6+0x1176ec)
> > #8 0x00007f1b2d6a37a6
> > llvm::DAGTypeLegalizer::CustomLowerNode(llvm::SDNode*, llvm::EVT,
> bool)
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x1247a6)
> > #9 0x00007f1b2d6be0d9
> > llvm::DAGTypeLegalizer::SplitVectorResult(llvm::SDNode*, unsigned
> int)
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x13f0d9)
> > #10 0x00007f1b2d69f156 llvm::DAGTypeLegalizer::run()
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x120156)
> > #11 0x00007f1b2d6a01ff llvm::SelectionDAG::LegalizeTypes()
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x1211ff)
> > #12 0x00007f1b2d785d42 llvm::SelectionDAGISel::CodeGenAndEmitDAG()
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x206d42)
> > #13 0x00007f1b2d790fd8
> > llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x211fd8)
> > #14 0x00007f1b2d7930e2
> > llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&)
> > [clone .part.873]
> > (/home/dev/llvm/build/bin/../lib/libLLVMSelectionDAG.so.6+0x2140e2)
> > #15 0x00007f1b35931d6a (anonymous
> > namespace)::HexagonDAGToDAGISel::runOnMachineFunction(llvm::
> MachineFunction&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMHexagonCodeGen.so.
> 6+0x116d6a)
> > #16 0x00007f1b2ef22585
> > llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMCodeGen.so.6+0x21f585)
> > #17 0x00007f1b2e922dd3
> > llvm::FPPassManager::runOnFunction(llvm::Function&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMCore.so.6+0x18ddd3)
> > #18 0x00007f1b2e922e93 llvm::FPPassManager::
> runOnModule(llvm::Module&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMCore.so.6+0x18de93)
> > #19 0x00007f1b2e9239e1 llvm::legacy::PassManagerImpl:
> :run(llvm::Module&)
> > (/home/dev/llvm/build/bin/../lib/libLLVMCore.so.6+0x18e9e1)
> > #20 0x000055b29c4ef3e2 compileModule(char**, llvm::LLVMContext&)
> > (/home/dev/llvm/build/./bin/llc+0x213e2)
> > #21 0x000055b29c4e23bc main (/home/dev/llvm/build/./bin/llc+0x143bc)
> > #22 0x00007f1b2c3d83f1 __libc_start_main
> > (/lib/x86_64-linux-gnu/libc.so.6+0x203f1)
> > #23 0x000055b29c4e256a _start (/home/dev/llvm/build/./bin/
> llc+0x1456a)
> > Stack dump:
> > 0. Program arguments: /home/dev/llvm/build/./bin/llc
> -march=hexagon
> > -mcpu=hexagonv5 -disable-hsdr
> > 1. Running pass 'Function Pass Manager' on module '<stdin>'.
> > 2. Running pass 'Hexagon DAG->DAG Pattern Instruction
> Selection' on
> > function '@run'
> > FileCheck error: '-' is empty.
> > FileCheck command line: /home/dev/llvm/build/./bin/FileCheck
> > /home/dev/llvm/llvm/test/CodeGen/Hexagon/vect/vect-cst-v4i32.ll
> >
> > How do I proceed to get the patch running all tests as expected? The
> > Tests directly focused on the results of the patch are passing
> without
> > problems.
> >
> > Cheers,
> > Michael
> >
> >
>
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