[llvm] aa2ddfc - [SampleFDO] For functions without profiles, provide an option to put
Artur Pilipenko via llvm-commits
llvm-commits at lists.llvm.org
Thu May 14 22:25:20 PDT 2020
Thanks!
Artur
On 14 May 2020, at 14:12, Wei Mi <wmi at google.com<mailto:wmi at google.com>> wrote:
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<mailto: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<mailto: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<mailto: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}
>
>
>
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