[lld] r232866 - [ELF] OrderPass : Order atoms only by ordinals.
Shankar Easwaran
shankare at codeaurora.org
Fri Mar 20 17:50:46 PDT 2015
I have another change to support --ctors-in-init-array, which will allow
sections by name .ctors to be placed in .init_array sections too.
This would also be used by linker scripts to support
SORT_BY_INIT_PRIORITY(*(.blah.*)) too.
Shankar Easwaran
On 3/20/2015 7:40 PM, Rui Ueyama wrote:
> OK. Maybe we should sort .init_array and fini_array section members
> unconditionally. Unlike atoms, the number of output sections is pretty
> small. This change seems a bit too clever than it needs to be. No need to
> parameterize this code for x86/x86-64.
>
> On Fri, Mar 20, 2015 at 5:31 PM, Shankar Easwaran <shankare at codeaurora.org>
> wrote:
>
>> The sorting is done by using the input section name. Sorting still holds
>> good.
>>
>>
>> On 3/20/2015 7:26 PM, Rui Ueyama wrote:
>>
>>> Oh, I'm not sure if this change is correct at all.
>>>
>>> Instead of sorting atoms, you sort output sections. Output sections are
>>> created, and its name is given by getOutputSection function. That function
>>> returns ".fini_array" for any input sections start with ".fini_array".
>>> Thus, all .fini_array input sections are binned to the same section
>>> *before* you sort them. So, sorting it is too late, no?
>>>
>>> I really don't like to see this kind of patch is submitted without review.
>>>
>>> On Fri, Mar 20, 2015 at 5:22 PM, Rui Ueyama <ruiu at google.com> wrote:
>>>
>>> This is non-trivial change, you should have sent this to pre-commit
>>>> review. Please do so next time. This change sacrificed readability a bit.
>>>> Also, I believe there's a bug in the code.
>>>>
>>>> On Fri, Mar 20, 2015 at 4:47 PM, Shankar Easwaran <
>>>> shankare at codeaurora.org
>>>>
>>>>> wrote:
>>>>> Author: shankare
>>>>> Date: Fri Mar 20 18:47:03 2015
>>>>> New Revision: 232866
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=232866&view=rev
>>>>> Log:
>>>>> [ELF] OrderPass : Order atoms only by ordinals.
>>>>>
>>>>> Move the init array/fini array sorting to the Output ELF writer.
>>>>>
>>>>> AFAIK, this is only needed by the X86_64/ARM ABI.
>>>>>
>>>>> This shaves time taken to self host lld by 0.2 seconds.
>>>>>
>>>>> Before patch
>>>>> ----------------
>>>>> 4791.062059 task-clock # 1.634 CPUs utilized
>>>>> ( +- 0.28% )
>>>>> 61,107 context-switches # 0.013 M/sec
>>>>> ( +- 0.56% )
>>>>> 2.932902671 seconds time elapsed
>>>>> ( +- 0.84% )
>>>>>
>>>>> After patch
>>>>> -------------
>>>>> 4608.417248 task-clock # 1.669 CPUs utilized
>>>>> ( +- 0.30% )
>>>>> 61,616 context-switches # 0.013 M/sec
>>>>> ( +- 0.63% )
>>>>> 2.761012703 seconds time elapsed
>>>>> ( +- 0.63% )
>>>>>
>>>>> Modified:
>>>>> lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
>>>>> lld/trunk/lib/ReaderWriter/ELF/OrderPass.h
>>>>> lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.h
>>>>> lld/trunk/test/elf/init_array-order.test
>>>>>
>>>>> Modified: lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/
>>>>> DefaultLayout.h?rev=232866&r1=232865&r2=232866&view=diff
>>>>>
>>>>> ============================================================
>>>>> ==================
>>>>> --- lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h (original)
>>>>> +++ lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h Fri Mar 20 18:47:03
>>>>> 2015
>>>>> @@ -316,13 +316,25 @@ public:
>>>>> return _copiedDynSymNames.count(sla->name());
>>>>> }
>>>>>
>>>>> + /// \brief Handle SORT_BY_PRIORITY.
>>>>> + void sortOutputSectionByPriority(StringRef outputSectionName,
>>>>> + StringRef prefix);
>>>>> +
>>>>> protected:
>>>>> + /// \brief TargetLayouts may use these functions to reorder the input
>>>>> sections
>>>>> + /// in a order defined by their ABI.
>>>>> + virtual void finalizeOutputSectionLayout() {}
>>>>> +
>>>>> /// \brief Allocate a new section.
>>>>> virtual AtomSection<ELFT> *createSection(
>>>>> StringRef name, int32_t contentType,
>>>>> DefinedAtom::ContentPermissions contentPermissions,
>>>>> SectionOrder sectionOrder);
>>>>>
>>>>> +private:
>>>>> + /// Helper function that returns the priority value from an input
>>>>> section.
>>>>> + uint32_t getPriorityFromSectionName(StringRef sectionName) const;
>>>>> +
>>>>> protected:
>>>>> llvm::BumpPtrAllocator _allocator;
>>>>> SectionMapT _sectionMap;
>>>>> @@ -657,13 +669,56 @@ template <class ELFT> void DefaultLayout
>>>>> }
>>>>> }
>>>>>
>>>>> +template <class ELFT>
>>>>> +uint32_t
>>>>> +DefaultLayout<ELFT>::getPriorityFromSectionName(StringRef sectionName)
>>>>> const {
>>>>> + StringRef priority = sectionName.drop_front().rsplit('.').second;
>>>>> + uint32_t prio;
>>>>> + if (priority.getAsInteger(10, prio))
>>>>> + return std::numeric_limits<uint32_t>::max();
>>>>> + return prio;
>>>>> +}
>>>>> +
>>>>> +template <class ELFT>
>>>>> +void DefaultLayout<ELFT>::sortOutputSectionByPriority(
>>>>> + StringRef outputSectionName, StringRef prefix) {
>>>>> + OutputSection<ELFT> *outputSection =
>>>>> findOutputSection(outputSectionName);
>>>>> + if (!outputSection)
>>>>> + return;
>>>>> +
>>>>> + auto sections = outputSection->sections();
>>>>> +
>>>>> + std::sort(sections.begin(), sections.end(),
>>>>> + [&](Chunk<ELFT> *lhs, Chunk<ELFT> *rhs) {
>>>>> + Section<ELFT> *lhsSection = dyn_cast<Section<ELFT>>(lhs);
>>>>> + Section<ELFT> *rhsSection = dyn_cast<Section<ELFT>>(rhs);
>>>>> + if (!lhsSection || !rhsSection)
>>>>> + return false;
>>>>> + StringRef lhsSectionName = lhsSection->inputSectionName()
>>>>> ;
>>>>> + StringRef rhsSectionName = rhsSection->inputSectionName()
>>>>> ;
>>>>> +
>>>>> + if (!prefix.empty()) {
>>>>> + if (!lhsSectionName.startswith(prefix) ||
>>>>> + !rhsSectionName.startswith(prefix))
>>>>> + return false;
>>>>> + }
>>>>>
>>>> + return getPriorityFromSectionName(lhsSectionName) <
>>>>
>>>>> + getPriorityFromSectionName(rhsSectionName);
>>>>> + });
>>>>>
>>>>> This sort does not preserve the original section order if they don't
>>>> start
>>>> with a given prefix.
>>>>
>>>> +};
>>>>
>>>>> +
>>>>> template <class ELFT> void
>>>>> DefaultLayout<ELFT>::assignSectionsToSegments() {
>>>>> ScopedTask task(getDefaultDomain(), "assignSectionsToSegments");
>>>>> ELFLinkingContext::OutputMagic outputMagic =
>>>>> _context.getOutputMagic();
>>>>> // sort the sections by their order as defined by the layout
>>>>> sortInputSections();
>>>>> +
>>>>> // Create output sections.
>>>>> createOutputSections();
>>>>> +
>>>>> + // Finalize output section layout.
>>>>> + finalizeOutputSectionLayout();
>>>>> +
>>>>> // Set the ordinal after sorting the sections
>>>>> int ordinal = 1;
>>>>> for (auto osi : _outputSections) {
>>>>>
>>>>> Modified: lld/trunk/lib/ReaderWriter/ELF/OrderPass.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/
>>>>> ReaderWriter/ELF/OrderPass.h?rev=232866&r1=232865&r2=232866&view=diff
>>>>>
>>>>> ============================================================
>>>>> ==================
>>>>> --- lld/trunk/lib/ReaderWriter/ELF/OrderPass.h (original)
>>>>> +++ lld/trunk/lib/ReaderWriter/ELF/OrderPass.h Fri Mar 20 18:47:03 2015
>>>>> @@ -17,49 +17,13 @@ namespace lld {
>>>>> namespace elf {
>>>>>
>>>>> /// \brief This pass sorts atoms by file and atom ordinals.
>>>>> -/// .{init,fini}_array.<priority> sections are handled specially.
>>>>> class OrderPass : public Pass {
>>>>> public:
>>>>> void perform(std::unique_ptr<MutableFile> &file) override {
>>>>> - MutableFile::DefinedAtomRange defined = file->definedAtoms();
>>>>> - auto last = std::partition(defined.begin(), defined.end(),
>>>>> isInitFini);
>>>>> - parallel_sort(defined.begin(), last, compareInitFini);
>>>>> - parallel_sort(last, defined.end(), DefinedAtom::
>>>>> compareByPosition);
>>>>> - }
>>>>> -
>>>>> -private:
>>>>> - static bool isInitFini(const DefinedAtom *atom) {
>>>>> - if (atom->sectionChoice() != DefinedAtom::sectionCustomRequired)
>>>>> - return false;
>>>>> - StringRef name = atom->customSectionName();
>>>>> - return name.startswith(".init_array") ||
>>>>> name.startswith(".fini_array");
>>>>> - }
>>>>> -
>>>>> - // Parses the number in .{init,fini}_array.<number>.
>>>>> - // Returns UINT32_MAX by default.
>>>>> - static uint32_t getPriority(const DefinedAtom *atom) {
>>>>> - StringRef sec = atom->customSectionName();
>>>>> - StringRef num = sec.drop_front().rsplit('.').second;
>>>>> - uint32_t prio;
>>>>> - if (num.getAsInteger(10, prio))
>>>>> - return std::numeric_limits<uint32_t>::max();
>>>>> - return prio;
>>>>> - }
>>>>> -
>>>>> - static bool compareInitFini(const DefinedAtom *lhs, const DefinedAtom
>>>>> *rhs) {
>>>>> - // Sort {.init_array, .fini_array}[.<num>] sections
>>>>> - // according to their number. Sections without optional
>>>>> - // numer suffix should go last.
>>>>> - uint32_t lp = getPriority(lhs);
>>>>> - uint32_t rp = getPriority(rhs);
>>>>> - if (lp != rp)
>>>>> - return lp < rp;
>>>>> -
>>>>> - // If both atoms have the same priority, fall back to default.
>>>>> - return DefinedAtom::compareByPosition(lhs, rhs);
>>>>> + parallel_sort(file->definedAtoms().begin(),
>>>>> file->definedAtoms().end(),
>>>>> + DefinedAtom::compareByPosition);
>>>>> }
>>>>> };
>>>>> -
>>>>> }
>>>>> }
>>>>>
>>>>>
>>>>> Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/
>>>>> ReaderWriter/ELF/X86_64/X86_64TargetHandler.h?rev=232866&
>>>>> r1=232865&r2=232866&view=diff
>>>>>
>>>>> ============================================================
>>>>> ==================
>>>>> --- lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.h
>>>>> (original)
>>>>> +++ lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.h Fri Mar
>>>>> 20 18:47:03 2015
>>>>> @@ -24,6 +24,11 @@ class X86_64TargetLayout : public Target
>>>>> public:
>>>>> X86_64TargetLayout(X86_64LinkingContext &context)
>>>>> : TargetLayout(context) {}
>>>>> +
>>>>> + void finalizeOutputSectionLayout() override {
>>>>> + sortOutputSectionByPriority(".init_array", ".init_array");
>>>>> + sortOutputSectionByPriority(".fini_array", ".fini_array");
>>>>>
>>>>> And you call the function twice. The result of the first invocation
>>>> would
>>>> be invalidated by the second invocation.
>>>>
>>>>
>>>> + }
>>>>> };
>>>>>
>>>>> class X86_64TargetHandler
>>>>>
>>>>> Modified: lld/trunk/test/elf/init_array-order.test
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/
>>>>> init_array-order.test?rev=232866&r1=232865&r2=232866&view=diff
>>>>>
>>>>> ============================================================
>>>>> ==================
>>>>> --- lld/trunk/test/elf/init_array-order.test (original)
>>>>> +++ lld/trunk/test/elf/init_array-order.test Fri Mar 20 18:47:03 2015
>>>>> @@ -1,6 +1,7 @@
>>>>> #RUN: yaml2obj -format=elf %s > %t
>>>>> #RUN: lld -flavor gnu -target x86_64-linux %t --noinhibit-exec \
>>>>> -#RUN: --output-filetype=yaml | FileCheck %s
>>>>> +#RUN: -o %t1.out
>>>>> +#RUN: llvm-objdump -s %t1.out | FileCheck %s
>>>>>
>>>>> !ELF
>>>>> FileHeader:
>>>>> @@ -62,12 +63,5 @@ Symbols:
>>>>> Type: STT_SECTION
>>>>> Section: .init_array
>>>>>
>>>>> -#CHECK: defined-atoms:
>>>>> -#CHECK: content: [ 01,
>>>>> -#CHECK: section-name: .init_array.1
>>>>> -#CHECK: content: [ 02,
>>>>> -#CHECK: section-name: .init_array.2
>>>>> -#CHECK: content: [ 03,
>>>>> -#CHECK: section-name: .init_array.3
>>>>> -#CHECK: content: [ 99,
>>>>> -#CHECK: section-name: .init_array
>>>>> +#CHECK: {{[0xa-f0-9]+}} 01000000 00000000 02000000 00000000
>>>>> +#CHECK: {{[0xa-f0-9]+}} 03000000 00000000 99000000 00000000
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>>
>>>>>
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>> by the Linux Foundation
>>
>>
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