reconcile hotness
diff --git a/llvm/include/llvm/Analysis/StaticDataProfileInfo.h b/llvm/include/llvm/Analysis/StaticDataProfileInfo.h
index d7bbf71..fbbc13a 100644
--- a/llvm/include/llvm/Analysis/StaticDataProfileInfo.h
+++ b/llvm/include/llvm/Analysis/StaticDataProfileInfo.h
@@ -14,8 +14,10 @@
/// profile information and provides methods to operate on them.
class StaticDataProfileInfo {
public:
- /// Accummulate the profile count of a constant that will be lowered to static
- /// data sections.
+ /// A constant and its profile count.
+ /// A constant is tracked if both conditions are met:
+ /// 1) It has local (i.e., private or internal) linkage.
+ // 2) Its data kind is one of {.rodata, .data, .bss, .data.rel.ro}.
DenseMap<const Constant *, uint64_t> ConstantProfileCounts;
/// Keeps track of the constants that are seen at least once without profile
@@ -26,11 +28,24 @@
LLVM_ABI std::optional<uint64_t>
getConstantProfileCount(const Constant *C) const;
- LLVM_ABI std::optional<StringRef>
- getDataHotnessBasedOnProfileCount(const Constant *C,
- const ProfileSummaryInfo *PSI) const;
+ enum class StaticDataHotness : uint8_t {
+ Cold = 0,
+ LukewarmOrUnknown = 1,
+ Hot = 2,
+ };
+
+ LLVM_ABI StaticDataHotness getSectionHotnessUsingProfileCount(
+ const Constant *C, const ProfileSummaryInfo *PSI, uint64_t Count) const;
+ LLVM_ABI StaticDataHotness
+ getSectionHotnessUsingDAP(std::optional<StringRef> SectionPrefix) const;
+
+ LLVM_ABI StringRef hotnessToStr(StaticDataHotness Hotness) const;
+
+ bool HasDataAccessProf = false;
public:
+ StaticDataProfileInfo(bool HasDataAccessProf)
+ : HasDataAccessProf(HasDataAccessProf) {}
StaticDataProfileInfo() = default;
/// If \p Count is not nullopt, add it to the profile count of the constant \p
@@ -40,14 +55,10 @@
LLVM_ABI void addConstantProfileCount(const Constant *C,
std::optional<uint64_t> Count);
- /// Return a section prefix for the constant \p C based on its profile count.
- /// - If a constant doesn't have a counter, return an empty string.
- /// - Otherwise,
- /// - If it has a hot count, return "hot".
- /// - If it is seen by unprofiled function, return an empty string.
- /// - If it has a cold count, return "unlikely".
- /// - Otherwise (e.g. it's used by lukewarm functions), return an empty
- /// string.
+ /// Given a constant \p C, returns a section prefix.
+ /// If \p C is a global variable, the section prefix is the bigger one
+ /// between its existing section prefix and its use profile count. Otherwise,
+ /// the section prefix is based on its use profile count.
LLVM_ABI StringRef getConstantSectionPrefix(
const Constant *C, const ProfileSummaryInfo *PSI) const;
};
diff --git a/llvm/include/llvm/IR/GlobalObject.h b/llvm/include/llvm/IR/GlobalObject.h
index 08a02b4..58138c79 100644
--- a/llvm/include/llvm/IR/GlobalObject.h
+++ b/llvm/include/llvm/IR/GlobalObject.h
@@ -121,9 +121,13 @@
/// appropriate default object file section.
LLVM_ABI void setSection(StringRef S);
- /// Set the section prefix for this global object.
+ /// Set the section prefix for this global object. If \p Prefix is empty,
+ /// the section prefix metadata will be cleared if it exists.
LLVM_ABI void setSectionPrefix(StringRef Prefix);
+ /// If \p Prefix is different from existing prefix, update section prefix. Returns true if an update happens and false otherwise.
+ LLVM_ABI bool updateSectionPrefix(StringRef Prefix);
+
/// Get the section prefix for this global object.
LLVM_ABI std::optional<StringRef> getSectionPrefix() const;
diff --git a/llvm/lib/Analysis/StaticDataProfileInfo.cpp b/llvm/lib/Analysis/StaticDataProfileInfo.cpp
index b7ca654..05b1adf 100644
--- a/llvm/lib/Analysis/StaticDataProfileInfo.cpp
+++ b/llvm/lib/Analysis/StaticDataProfileInfo.cpp
@@ -1,11 +1,17 @@
#include "llvm/Analysis/StaticDataProfileInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/ProfileData/InstrProf.h"
using namespace llvm;
+
+extern cl::opt<bool> AnnotateStaticDataSectionPrefix;
+
void StaticDataProfileInfo::addConstantProfileCount(
const Constant *C, std::optional<uint64_t> Count) {
if (!Count) {
@@ -28,65 +34,79 @@
return I->second;
}
-std::optional<StringRef>
-StaticDataProfileInfo::getDataHotnessBasedOnProfileCount(
- const Constant *C, const ProfileSummaryInfo *PSI) const {
- auto Count = getConstantProfileCount(C);
- // The constant `C` doesn't have a profile count. `C` might be a external
- // linkage global variable, whose PGO-based counter is not tracked within one
- // IR module.
- if (!Count)
- return std::nullopt;
+StaticDataProfileInfo::StaticDataHotness
+StaticDataProfileInfo::getSectionHotnessUsingProfileCount(
+ const Constant *C, const ProfileSummaryInfo *PSI, uint64_t Count) const {
// The accummulated counter shows the constant is hot. Return 'hot' whether
// this variable is seen by unprofiled functions or not.
- if (PSI->isHotCount(*Count))
- return "hot";
+ if (PSI->isHotCount(Count))
+ return StaticDataHotness::Hot;
// The constant is not hot, and seen by unprofiled functions. We don't want to
// assign it to unlikely sections, even if the counter says 'cold'. So return
// an empty prefix before checking whether the counter is cold.
if (ConstantWithoutCounts.count(C))
- return std::nullopt;
+ return StaticDataHotness::LukewarmOrUnknown;
// The accummulated counter shows the constant is cold. Return 'unlikely'.
- if (PSI->isColdCount(*Count)) {
+ if (PSI->isColdCount(Count))
+ return StaticDataHotness::Cold;
+
+ return StaticDataHotness::LukewarmOrUnknown;
+}
+
+StringRef StaticDataProfileInfo::hotnessToStr(
+ StaticDataProfileInfo::StaticDataHotness Hotness) const {
+ switch (Hotness) {
+ case StaticDataProfileInfo::StaticDataHotness::Cold:
return "unlikely";
- }
- return "";
-}
-
-static StringRef reconcileHotness(StringRef SectionPrefix, StringRef Hotness) {
- assert((SectionPrefix == "hot" || SectionPrefix == "unlikely") &&
- "Section prefix must be 'hot' or 'unlikely'");
-
- if (SectionPrefix == "hot" || Hotness == "hot")
+ case StaticDataProfileInfo::StaticDataHotness::Hot:
return "hot";
- assert(SectionPrefix == "unlikely" && "Section prefix must be 'unlikely'.");
- return Hotness;
+ default:
+ return "";
+ }
}
-static StringRef
-reconcileOptionalHotness(std::optional<StringRef> SectionPrefix,
- std::optional<StringRef> Hotness) {
- if (!SectionPrefix)
- return Hotness.value_or("");
- if (!Hotness)
- return SectionPrefix.value_or("");
-
- return reconcileHotness(*SectionPrefix, *Hotness);
+StaticDataProfileInfo::StaticDataHotness
+StaticDataProfileInfo::getSectionHotnessUsingDAP(
+ std::optional<StringRef> MaybeSectionPrefix) const {
+ if (!MaybeSectionPrefix)
+ return StaticDataProfileInfo::StaticDataHotness::LukewarmOrUnknown;
+ StringRef Prefix = *MaybeSectionPrefix;
+ assert((Prefix == "hot" || Prefix == "unlikely") &&
+ "Expect section_prefix to be one of hot or unlikely");
+ return Prefix == "hot" ? StaticDataProfileInfo::StaticDataHotness::Hot
+ : StaticDataProfileInfo::StaticDataHotness::Cold;
}
StringRef StaticDataProfileInfo::getConstantSectionPrefix(
const Constant *C, const ProfileSummaryInfo *PSI) const {
- std::optional<StringRef> HotnessBasedOnCount =
- getDataHotnessBasedOnProfileCount(C, PSI);
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
- return reconcileOptionalHotness(GV->getSectionPrefix(),
- HotnessBasedOnCount);
+ auto Count = getConstantProfileCount(C);
- return HotnessBasedOnCount.value_or("");
+ if (HasDataAccessProf) {
+ // Module flag `HasDataAccessProf` is 1 -> empty section prefix means uknown
+ // hotness except for string literals.
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(C);
+ GV && !GV->getName().starts_with(".str")) {
+ auto HotnessFromDAP = getSectionHotnessUsingDAP(GV->getSectionPrefix());
+
+ if (!Count)
+ return hotnessToStr(HotnessFromDAP);
+
+ auto HotnessFromPGO = getSectionHotnessUsingProfileCount(C, PSI, *Count);
+ return hotnessToStr(std::max(HotnessFromDAP, HotnessFromPGO));
+ }
+ }
+
+ if (!Count)
+ return "";
+ return hotnessToStr(getSectionHotnessUsingProfileCount(C, PSI, *Count));
}
bool StaticDataProfileInfoWrapperPass::doInitialization(Module &M) {
- Info.reset(new StaticDataProfileInfo());
+ bool HasDataAccessProf = false;
+ if (auto *MD = mdconst::extract_or_null<ConstantInt>(
+ M.getModuleFlag("HasDataAccessProf")))
+ HasDataAccessProf = MD->getZExtValue();
+ Info.reset(new StaticDataProfileInfo(HasDataAccessProf));
return false;
}
diff --git a/llvm/lib/CodeGen/StaticDataAnnotator.cpp b/llvm/lib/CodeGen/StaticDataAnnotator.cpp
index fdf48e1..72735d2 100644
--- a/llvm/lib/CodeGen/StaticDataAnnotator.cpp
+++ b/llvm/lib/CodeGen/StaticDataAnnotator.cpp
@@ -31,6 +31,8 @@
#include "llvm/Analysis/StaticDataProfileInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/Analysis.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
@@ -79,11 +81,7 @@
continue;
StringRef SectionPrefix = SDPI->getConstantSectionPrefix(&GV, PSI);
- if (SectionPrefix.empty())
- continue;
-
- GV.setSectionPrefix(SectionPrefix);
- Changed = true;
+ Changed |= GV.updateSectionPrefix(SectionPrefix);
}
return Changed;
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 11d33e2..0731fcb 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -289,11 +289,28 @@
}
void GlobalObject::setSectionPrefix(StringRef Prefix) {
+ if (Prefix.empty()) {
+ setMetadata(LLVMContext::MD_section_prefix, nullptr);
+ return;
+ }
MDBuilder MDB(getContext());
setMetadata(LLVMContext::MD_section_prefix,
MDB.createGlobalObjectSectionPrefix(Prefix));
}
+bool GlobalObject::updateSectionPrefix(StringRef Prefix) {
+ auto MD = getMetadata(LLVMContext::MD_section_prefix);
+ StringRef ExistingPrefix; // Empty by default.
+ if (MD != nullptr)
+ ExistingPrefix = cast<MDString>(MD->getOperand(1))->getString();
+
+ if (ExistingPrefix != Prefix) {
+ setSectionPrefix(Prefix);
+ return true;
+ }
+ return false;
+}
+
std::optional<StringRef> GlobalObject::getSectionPrefix() const {
if (MDNode *MD = getMetadata(LLVMContext::MD_section_prefix)) {
[[maybe_unused]] StringRef MDName =
diff --git a/llvm/lib/ProfileData/DataAccessProf.cpp b/llvm/lib/ProfileData/DataAccessProf.cpp
index a1e686b..d16d0b6f 100644
--- a/llvm/lib/ProfileData/DataAccessProf.cpp
+++ b/llvm/lib/ProfileData/DataAccessProf.cpp
@@ -1,6 +1,7 @@
#include "llvm/ProfileData/DataAccessProf.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ProfileData/InstrProf.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compression.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Errc.h"
@@ -9,6 +10,9 @@
#include "llvm/Support/raw_ostream.h"
namespace llvm {
+cl::opt<bool> AnnotateStaticDataSectionPrefix(
+ "memprof-annotate-static-data-prefix", cl::init(false), cl::Hidden,
+ cl::desc("If true, annotate the static data section prefix"));
namespace memprof {
// If `Map` has an entry keyed by `Str`, returns the entry iterator. Otherwise,
diff --git a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp b/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
index ecb2f2d..789396c 100644
--- a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
@@ -41,6 +41,7 @@
#define DEBUG_TYPE "memprof"
namespace llvm {
+extern cl::opt<bool> AnnotateStaticDataSectionPrefix;
extern cl::opt<bool> PGOWarnMissing;
extern cl::opt<bool> NoPGOWarnMismatch;
extern cl::opt<bool> NoPGOWarnMismatchComdatWeak;
@@ -76,10 +77,6 @@
"memprof-matching-cold-threshold", cl::init(100), cl::Hidden,
cl::desc("Min percent of cold bytes matched to hint allocation cold"));
-static cl::opt<bool> AnnotateStaticDataSectionPrefix(
- "memprof-annotate-static-data-prefix", cl::init(false), cl::Hidden,
- cl::desc("If true, annotate the static data section prefix"));
-
// Matching statistics
STATISTIC(NumOfMemProfMissing, "Number of functions without memory profile.");
STATISTIC(NumOfMemProfMismatch,
@@ -797,7 +794,11 @@
if (!AnnotateStaticDataSectionPrefix || M.globals().empty())
return false;
+ // The module flag helps codegen passes interpret empty section prefix:
+ // - 0 : empty section prefix is expected for each GV.
+ // - 1 : empty section prefix means the GV has unknown hotness.
if (!DataAccessProf) {
+ M.addModuleFlag(Module::Warning, "HasDataAccessProf", 0U);
M.getContext().diagnose(DiagnosticInfoPGOProfile(
MemoryProfileFileName.data(),
StringRef("Data access profiles not found in memprof. Ignore "
@@ -806,6 +807,8 @@
return false;
}
+ M.addModuleFlag(Module::Warning, "HasDataAccessProf", 1);
+
bool Changed = false;
// Iterate all global variables in the module and annotate them based on
// data access profiles. Note it's up to the linker to decide how to map input
diff --git a/llvm/test/CodeGen/X86/global-variable-partition.ll b/llvm/test/CodeGen/X86/global-variable-partition.ll
index 63d37f2..8a81481 100644
--- a/llvm/test/CodeGen/X86/global-variable-partition.ll
+++ b/llvm/test/CodeGen/X86/global-variable-partition.ll
@@ -109,9 +109,9 @@
; section prefix. PGO counter analysis categorizes it as cold, so it will have
; section name `.data.unlikely`.
; COMMON: .type data3,@object
-; SYM-NEXT: .section .data.unlikely.data3,"aw",@progbits
-; UNIQ-NEXT: .section .data.unlikely.,"aw",@progbits,unique,8
-; AGG-NEXT: .section .data.unlikely.,"aw",@progbits
+; SYM-NEXT: .section .data.data3,"aw",@progbits
+; UNIQ-NEXT: .section .data,"aw",@progbits,unique,8
+; AGG-NEXT: .data
; For @data_with_unknown_hotness
; SYM: .type .Ldata_with_unknown_hotness,@object # @data_with_unknown_hotness
@@ -119,8 +119,6 @@
; UNIQ: .section .data,"aw",@progbits,unique,9
; The `.section` directive is omitted for .data with -unique-section-names=false.
; See MCSectionELF::shouldOmitSectionDirective for the implementation details.
-; AGG: .data
-; COMMON: .Ldata_with_unknown_hotness:
; For @hot_data_custom_bar_section
; It has an explicit section attribute 'var' and shouldn't have hot or unlikely suffix.
@@ -130,20 +128,27 @@
; UNIQ: .section bar,"aw",@progbits
; AGG: .section bar,"aw",@progbits
+; For @external_cold_bss
+; COMMON: .type external_cold_bss,@object
+; SYM-NEXT: .section .bss.external_cold_bss,"aw",@nobits
+; UNIQ-NEXT: .section .bss,"aw",@nobits,unique,
+; AVG-NEXT: .bss
+
@.str = private unnamed_addr constant [5 x i8] c"hot\09\00", align 1
@.str.1 = private unnamed_addr constant [10 x i8] c"%d\09%d\09%d\0A\00", align 1
@hot_relro_array = internal constant [2 x ptr] [ptr @bss2, ptr @data3]
@hot_data = internal global i32 5
@hot_bss = internal global i32 0
@.str.2 = private unnamed_addr constant [14 x i8] c"cold%d\09%d\09%d\0A\00", align 1
-@cold_bss = internal global i32 0
-@cold_data = internal global i32 4
+@cold_bss = internal global i32 0, !section_prefix !18
+@cold_data = internal global i32 4, !section_prefix !18
@cold_data_custom_foo_section = internal global i32 100, section "foo"
-@cold_relro_array = internal constant [2 x ptr] [ptr @data3, ptr @bss2]
+@cold_relro_array = internal constant [2 x ptr] [ptr @data3, ptr @bss2], !section_prefix !18
@bss2 = internal global i32 0, !section_prefix !17
@data3 = internal global i32 3
@data_with_unknown_hotness = private global i32 5
@hot_data_custom_bar_section = internal global i32 101 #0
+@external_cold_bss = global i32 0
define void @cold_func(i32 %0) !prof !15 {
%2 = load i32, ptr @cold_bss
@@ -156,7 +161,8 @@
%9 = load i32, ptr @data_with_unknown_hotness
%11 = load i32, ptr @hot_data
%12 = load i32, ptr @cold_data_custom_foo_section
- %13 = call i32 (...) @func_taking_arbitrary_param(ptr @.str.2, i32 %2, i32 %3, i32 %8, i32 %9, i32 %11, i32 %12)
+ %val = load i32, ptr @external_cold_bss
+ %13 = call i32 (...) @func_taking_arbitrary_param(ptr @.str.2, i32 %2, i32 %3, i32 %8, i32 %9, i32 %11, i32 %12, i32 %val)
ret void
}
@@ -216,8 +222,9 @@
attributes #0 = {"data-section"="bar"}
-!llvm.module.flags = !{!1}
+!llvm.module.flags = !{!0, !1}
+!0 = !{i32 2, !"HasDataAccessProf", i32 1}
!1 = !{i32 1, !"ProfileSummary", !2}
!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
!3 = !{!"ProfileFormat", !"InstrProf"}
@@ -235,3 +242,5 @@
!15 = !{!"function_entry_count", i64 1}
!16 = !{!"branch_weights", i32 1, i32 99999}
!17 = !{!"section_prefix", !"hot"}
+!18 = !{!"section_prefix", !"unlikely"}
+
