[llvm] aa2ddfc - [SampleFDO] For functions without profiles, provide an option to put
Wei Mi via llvm-commits
llvm-commits at lists.llvm.org
Tue May 12 10:31:58 PDT 2020
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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