[llvm] aa2ddfc - [SampleFDO] For functions without profiles, provide an option to put
Wei Mi via llvm-commits
llvm-commits at lists.llvm.org
Thu May 14 14:12:45 PDT 2020
Artur, I have renamed the flag in llvm-profdata:
https://github.com/llvm/llvm-project/commit/56926ae0faa67ac4c3b75609bfeea2eb324c0851
Thanks,
Wei.
On Tue, May 12, 2020 at 10:31 AM Wei Mi <wmi at google.com> wrote:
> Thanks Artur for letting me know the problem. I will prepare a patch to
> fix it.
>
> Wei.
>
> On Tue, May 12, 2020 at 9:50 AM Artur Pilipenko <apilipenko at azul.com>
> wrote:
>
>> Hi Wei,
>>
>> This change introduces a cl::opt partial-profile which conflicts with
>> partial-profile option in llvm-profdata tool. The conflict happens in
>> builds with LLVM_LINK_LLVM_DYLIB enabled. In this case the tools are linked
>> with libLLVM and we end up with two definitions for the same cl::opt.
>>
>> Can we rename one of the options to avoid this?
>>
>> Artur
>>
>> > On 8 May 2020, at 11:30, Wei Mi via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>> >
>> >
>> > Author: Wei Mi
>> > Date: 2020-05-08T11:18:09-07:00
>> > New Revision: aa2ddfc73d6e4a3369b7992aecaf107987c505b6
>> >
>> > URL:
>> https://github.com/llvm/llvm-project/commit/aa2ddfc73d6e4a3369b7992aecaf107987c505b6
>> > DIFF:
>> https://github.com/llvm/llvm-project/commit/aa2ddfc73d6e4a3369b7992aecaf107987c505b6.diff
>> >
>> > LOG: [SampleFDO] For functions without profiles, provide an option to
>> put
>> > them in a special text section.
>> >
>> > For sampleFDO, because the optimized build uses profile generated from
>> > previous release, previously we couldn't tell a function without profile
>> > was truely cold or just newly created so we had to treat them
>> conservatively
>> > and put them in .text section instead of .text.unlikely. The result was
>> when
>> > we persuing the best performance by locking .text.hot and .text in
>> memory,
>> > we wasted a lot of memory to keep cold functions inside.
>> >
>> > In https://reviews.llvm.org/D66374, we introduced profile symbol list
>> to
>> > discriminate functions being cold versus functions being newly added.
>> > This mechanism works quite well for regular use cases in AutoFDO.
>> However,
>> > in some case, we can only have a partial profile when optimizing a
>> target.
>> > The partial profile may be an aggregated profile collected from many
>> targets.
>> > The profile symbol list method used for regular sampleFDO profile is not
>> > applicable to partial profile use case because it may be too large and
>> > introduce many false positives.
>> >
>> > To solve the problem for partial profile use case, we provide an option
>> called
>> > --profile-unknown-in-special-section. For functions without profile, we
>> will
>> > still treat them conservatively in compiler optimizations -- for
>> example,
>> > treat them as warm instead of cold in inliner. When we use profile info
>> to
>> > add section prefix for functions, we will discriminate functions known
>> to be
>> > not cold versus functions without profile (being unknown), and we will
>> put
>> > functions being unknown in a special text section called .text.unknown.
>> > Runtime system will have the flexibility to decide where to put the
>> special
>> > section in order to achieve a balance between performance and memory
>> saving.
>> >
>> > Differential Revision: https://reviews.llvm.org/D62540
>> >
>> > Added:
>> >
>> >
>> > Modified:
>> > llvm/include/llvm/Analysis/ProfileSummaryInfo.h
>> > llvm/lib/Analysis/ProfileSummaryInfo.cpp
>> > llvm/lib/CodeGen/CodeGenPrepare.cpp
>> > llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
>> >
>> > Removed:
>> >
>> >
>> >
>> >
>> ################################################################################
>> > diff --git a/llvm/include/llvm/Analysis/ProfileSummaryInfo.h
>> b/llvm/include/llvm/Analysis/ProfileSummaryInfo.h
>> > index e293d069f1f1..8fbc9e8990b2 100644
>> > --- a/llvm/include/llvm/Analysis/ProfileSummaryInfo.h
>> > +++ b/llvm/include/llvm/Analysis/ProfileSummaryInfo.h
>> > @@ -72,13 +72,6 @@ class ProfileSummaryInfo {
>> > Summary->getKind() == ProfileSummary::PSK_Sample;
>> > }
>> >
>> > - /// Returns true if module \c M has partial-profile sample profile.
>> > - bool hasPartialSampleProfile() {
>> > - return hasProfileSummary() &&
>> > - Summary->getKind() == ProfileSummary::PSK_Sample &&
>> > - Summary->isPartialProfile();
>> > - }
>> > -
>> > /// Returns true if module \c M has instrumentation profile.
>> > bool hasInstrumentationProfile() {
>> > return hasProfileSummary() &&
>> > @@ -106,6 +99,8 @@ class ProfileSummaryInfo {
>> > Optional<uint64_t> getProfileCount(const CallBase &CallInst,
>> > BlockFrequencyInfo *BFI,
>> > bool AllowSynthetic = false);
>> > + /// Returns true if module \c M has partial-profile sample profile.
>> > + bool hasPartialSampleProfile();
>> > /// Returns true if the working set size of the code is considered
>> huge.
>> > bool hasHugeWorkingSetSize();
>> > /// Returns true if the working set size of the code is considered
>> large.
>> > @@ -118,6 +113,8 @@ class ProfileSummaryInfo {
>> > bool isFunctionEntryCold(const Function *F);
>> > /// Returns true if \p F contains only cold code.
>> > bool isFunctionColdInCallGraph(const Function *F, BlockFrequencyInfo
>> &BFI);
>> > + /// Returns true if the hotness of \p F is unknown.
>> > + bool isFunctionHotnessUnknown(const Function &F);
>> > /// Returns true if \p F contains hot code with regard to a given hot
>> > /// percentile cutoff value.
>> > bool isFunctionHotInCallGraphNthPercentile(int PercentileCutoff,
>> >
>> > diff --git a/llvm/lib/Analysis/ProfileSummaryInfo.cpp
>> b/llvm/lib/Analysis/ProfileSummaryInfo.cpp
>> > index dd53aa78f40f..ef33b9b1de5a 100644
>> > --- a/llvm/lib/Analysis/ProfileSummaryInfo.cpp
>> > +++ b/llvm/lib/Analysis/ProfileSummaryInfo.cpp
>> > @@ -66,6 +66,10 @@ static cl::opt<int> ProfileSummaryColdCount(
>> > cl::desc("A fixed cold count that overrides the count derived from"
>> > " profile-summary-cutoff-cold"));
>> >
>> > +static cl::opt<bool> PartialProfile(
>> > + "partial-profile", cl::Hidden, cl::init(false),
>> > + cl::desc("Specify the current profile is used as a partial
>> profile."));
>> > +
>> > // Find the summary entry for a desired percentile of counts.
>> > static const ProfileSummaryEntry
>> &getEntryForPercentile(SummaryEntryVector &DS,
>> > uint64_t
>> Percentile) {
>> > @@ -192,6 +196,11 @@ bool
>> ProfileSummaryInfo::isFunctionColdInCallGraph(const Function *F,
>> > return true;
>> > }
>> >
>> > +bool ProfileSummaryInfo::isFunctionHotnessUnknown(const Function &F) {
>> > + assert(hasPartialSampleProfile() && "Expect partial sample profile");
>> > + return !F.getEntryCount().hasValue();
>> > +}
>> > +
>> > template<bool isHot>
>> > bool ProfileSummaryInfo::isFunctionHotOrColdInCallGraphNthPercentile(
>> > int PercentileCutoff, const Function *F, BlockFrequencyInfo &BFI) {
>> > @@ -399,6 +408,12 @@ bool ProfileSummaryInfo::isColdCallSite(const
>> CallBase &CB,
>> > return hasSampleProfile() && CB.getCaller()->hasProfileData();
>> > }
>> >
>> > +bool ProfileSummaryInfo::hasPartialSampleProfile() {
>> > + return hasProfileSummary() &&
>> > + Summary->getKind() == ProfileSummary::PSK_Sample &&
>> > + (PartialProfile || Summary->isPartialProfile());
>> > +}
>> > +
>> > INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
>> > "Profile summary info", false, true)
>> >
>> >
>> > diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp
>> b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>> > index 359618d6669a..eceee30c532f 100644
>> > --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
>> > +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>> > @@ -177,6 +177,17 @@ static cl::opt<bool> ProfileGuidedSectionPrefix(
>> > "profile-guided-section-prefix", cl::Hidden, cl::init(true),
>> cl::ZeroOrMore,
>> > cl::desc("Use profile info to add section prefix for hot/cold
>> functions"));
>> >
>> > +static cl::opt<bool> ProfileUnknownInSpecialSection(
>> > + "profile-unknown-in-special-section", cl::Hidden, cl::init(false),
>> > + cl::ZeroOrMore,
>> > + cl::desc("In profiling mode like sampleFDO, if a function doesn't
>> have "
>> > + "profile, we cannot tell the function is cold for sure
>> because "
>> > + "it may be a function newly added without ever being
>> sampled. "
>> > + "With the flag enabled, compiler can put such profile
>> unknown "
>> > + "functions into a special section, so runtime system can
>> choose "
>> > + "to handle it in a
>> > diff erent way than .text section, to save "
>> > + "RAM for example. "));
>> > +
>> > static cl::opt<unsigned> FreqRatioToSkipMerge(
>> > "cgp-freq-ratio-to-skip-merge", cl::Hidden, cl::init(2),
>> > cl::desc("Skip merging empty blocks if (frequency of empty block) /
>> "
>> > @@ -452,6 +463,9 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
>> > F.setSectionPrefix(".hot");
>> > else if (PSI->isFunctionColdInCallGraph(&F, *BFI))
>> > F.setSectionPrefix(".unlikely");
>> > + else if (ProfileUnknownInSpecialSection &&
>> PSI->hasPartialSampleProfile() &&
>> > + PSI->isFunctionHotnessUnknown(F))
>> > + F.setSectionPrefix(".unknown");
>> > }
>> >
>> > /// This optimization identifies DIV instructions that can be
>> >
>> > diff --git
>> a/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
>> b/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
>> > index 82c407ebb9d2..6ac39a167689 100644
>> > --- a/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
>> > +++ b/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
>> > @@ -1,5 +1,6 @@
>> > ; REQUIRES: x86-registered-target
>> > ; RUN: opt < %s -sample-profile
>> -sample-profile-file=%S/Inputs/inline.prof -codegenprepare -S | FileCheck %s
>> > +; RUN: opt < %s -sample-profile
>> -sample-profile-file=%S/Inputs/inline.prof -codegenprepare
>> -profile-unknown-in-special-section -partial-profile -S | FileCheck %s
>> --check-prefix UNKNOWN
>> > ; RUN: opt < %s -sample-profile
>> -sample-profile-file=%S/Inputs/inline.prof -codegenprepare
>> -profile-sample-accurate -S | FileCheck %s --check-prefix ACCURATE
>> >
>> > target triple = "x86_64-pc-linux-gnu"
>> > @@ -11,7 +12,8 @@ target triple = "x86_64-pc-linux-gnu"
>> > declare void @hot_func()
>> >
>> > ; CHECK-NOT: foo_not_in_profile{{.*}}!section_prefix
>> > -; CHECK: foo_not_in_profile{{.*}}!prof ![[UNKNOWN_ID:[0-9]+]]
>> > +; CHECK: foo_not_in_profile{{.*}}!prof ![[NOPROFILE_ID:[0-9]+]]
>> > +; UNKNOWN: foo_not_in_profile{{.*}}!prof ![[NOPROFILE_ID:[0-9]+]]
>> !section_prefix ![[UNKNOWN_ID:[0-9]+]]
>> > ; ACCURATE: foo_not_in_profile{{.*}}!prof ![[ZERO_ID:[0-9]+]]
>> !section_prefix ![[COLD_ID:[0-9]+]]
>> > ; The function not appearing in profile is cold when
>> -profile-sample-accurate
>> > ; is on.
>> > @@ -31,9 +33,11 @@ define void @bar_not_in_profile() #0 {
>> >
>> > attributes #0 = { "profile-sample-accurate" }
>> >
>> > -; CHECK: ![[UNKNOWN_ID]] = !{!"function_entry_count", i64 -1}
>> > +; CHECK: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
>> > ; CHECK: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
>> > ; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !".unlikely"}
>> > +; UNKNOWN: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
>> > +; UNKNOWN: ![[UNKNOWN_ID]] = !{!"function_section_prefix", !".unknown"}
>> > ; ACCURATE: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
>> > ; ACCURATE: ![[COLD_ID]] = !{!"function_section_prefix", !".unlikely"}
>> > !llvm.module.flags = !{!1}
>> >
>> >
>> >
>> > _______________________________________________
>> > llvm-commits mailing list
>> > llvm-commits at lists.llvm.org
>> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>>
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