[StaticDataLayout] Factor out a helper function for section prefix eligibility and use it in both optimizer and codegen

llvm/include/llvm/Analysis/StaticDataProfileInfo.h

@@ -10,6 +10,24 @@
 
 namespace llvm {
 
+namespace memprof {
+// Represents the eligibility status of a global variable for section prefix
+// annotation. Other than AnnotationOk, each enum value indicates a specific
+// reason for ineligibility.
+enum class AnnotationKind : uint8_t {
+  AnnotationOK,
+  DeclForLinker,
+  ExplicitSection,
+  ReservedName,
+};
+/// Returns the annotation kind of the global variable \p GV.
+AnnotationKind getAnnotationKind(const GlobalVariable &GV);
+
+/// Returns true if the annotation kind of the global variable \p GV is
+/// AnnotationOK.
+bool IsAnnotationOK(const GlobalVariable &GV);
+} // namespace memprof
+
 /// A class that holds the constants that represent static data and their
 /// profile information and provides methods to operate on them.
 class StaticDataProfileInfo {

llvm/lib/Analysis/StaticDataProfileInfo.cpp

@@ -6,6 +6,43 @@
 #include "llvm/ProfileData/InstrProf.h"
 
 using namespace llvm;
+
+namespace llvm {
+namespace memprof {
+// Returns true iff the global variable has custom section either by
+// __attribute__((section("name")))
+// (https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate)
+// or #pragma clang section directives
+// (https://clang.llvm.org/docs/LanguageExtensions.html#specifying-section-names-for-global-objects-pragma-clang-section).
+static bool hasExplicitSectionName(const GlobalVariable &GVar) {
+  if (GVar.hasSection())
+    return true;
+
+  auto Attrs = GVar.getAttributes();
+  if (Attrs.hasAttribute("bss-section") || Attrs.hasAttribute("data-section") ||
+      Attrs.hasAttribute("relro-section") ||
+      Attrs.hasAttribute("rodata-section"))
+    return true;
+  return false;
+}
+
+AnnotationKind getAnnotationKind(const GlobalVariable &GV) {
+  if (GV.isDeclarationForLinker())
+    return AnnotationKind::DeclForLinker;
+  StringRef Name = GV.getName();
+  if (Name.starts_with("llvm."))
+    return AnnotationKind::ReservedName;
+  if (hasExplicitSectionName(GV))
+    return AnnotationKind::ExplicitSection;
+  return AnnotationKind::AnnotationOK;
+}
+
+bool IsAnnotationOK(const GlobalVariable &GV) {
+  return getAnnotationKind(GV) == AnnotationKind::AnnotationOK;
+}
+} // namespace memprof
+} // namespace llvm
+
 void StaticDataProfileInfo::addConstantProfileCount(
     const Constant *C, std::optional<uint64_t> Count) {
   if (!Count) {

llvm/lib/CodeGen/StaticDataAnnotator.cpp

@@ -75,7 +75,7 @@ bool StaticDataAnnotator::runOnModule(Module &M) {
 
   bool Changed = false;
   for (auto &GV : M.globals()) {
-    if (GV.isDeclarationForLinker())
+    if (!llvm::memprof::IsAnnotationOK(GV))
       continue;
 
     // The implementation below assumes prior passes don't set section prefixes,

llvm/lib/Transforms/Instrumentation/MemProfUse.cpp

@@ -17,6 +17,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/MemoryProfileInfo.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
+#include "llvm/Analysis/StaticDataProfileInfo.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Function.h"
@@ -775,36 +776,21 @@ PreservedAnalyses MemProfUsePass::run(Module &M, ModuleAnalysisManager &AM) {
   return PreservedAnalyses::none();
 }
 
-// Returns true iff the global variable has custom section either by
-// __attribute__((section("name")))
-// (https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate)
-// or #pragma clang section directives
-// (https://clang.llvm.org/docs/LanguageExtensions.html#specifying-section-names-for-global-objects-pragma-clang-section).
-static bool hasExplicitSectionName(const GlobalVariable &GVar) {
-  if (GVar.hasSection())
-    return true;
-
-  auto Attrs = GVar.getAttributes();
-  if (Attrs.hasAttribute("bss-section") || Attrs.hasAttribute("data-section") ||
-      Attrs.hasAttribute("relro-section") ||
-      Attrs.hasAttribute("rodata-section"))
-    return true;
-  return false;
-}
-
 bool MemProfUsePass::annotateGlobalVariables(
     Module &M, const memprof::DataAccessProfData *DataAccessProf) {
   if (!AnnotateStaticDataSectionPrefix || M.globals().empty())
     return false;
 
   if (!DataAccessProf) {
+    M.addModuleFlag(Module::Warning, "EnableDataAccessProf", 0U);
     M.getContext().diagnose(DiagnosticInfoPGOProfile(
         MemoryProfileFileName.data(),
         StringRef("Data access profiles not found in memprof. Ignore "
                   "-memprof-annotate-static-data-prefix."),
         DS_Warning));
     return false;
   }
+  M.addModuleFlag(Module::Warning, "EnableDataAccessProf", 1U);
 
   bool Changed = false;
   // Iterate all global variables in the module and annotate them based on
@@ -815,13 +801,16 @@ bool MemProfUsePass::annotateGlobalVariables(
   for (GlobalVariable &GVar : M.globals()) {
     assert(!GVar.getSectionPrefix().has_value() &&
            "GVar shouldn't have section prefix yet");
-    if (GVar.isDeclarationForLinker())
-      continue;
-
-    if (hasExplicitSectionName(GVar)) {
+    auto Kind = llvm::memprof::getAnnotationKind(GVar);
+    switch (Kind) {
+    case llvm::memprof::AnnotationKind::AnnotationOK:
+      break;
+    case llvm::memprof::AnnotationKind::ExplicitSection:
       ++NumOfMemProfExplicitSectionGlobalVars;
       LLVM_DEBUG(dbgs() << "Global variable " << GVar.getName()
                         << " has explicit section name. Skip annotating.\n");
+      [[fallthrough]];
+    default:
       continue;
     }
 
@@ -831,7 +820,6 @@ bool MemProfUsePass::annotateGlobalVariables(
     // TODO: Track string content hash in the profiles and compute it inside the
     // compiler to categeorize the hotness string literals.
     if (Name.starts_with(".str")) {
-
       LLVM_DEBUG(dbgs() << "Skip annotating string literal " << Name << "\n");
       continue;
     }

llvm/test/Transforms/PGOProfile/data-access-profile.ll

@@ -3,22 +3,28 @@
 
 ; RUN: rm -rf %t && split-file %s %t && cd %t
 
-;; Read a text profile and merge it into indexed profile.
+;; Read text profiles and merge them into indexed profiles.
 ; RUN: llvm-profdata merge --memprof-version=4 memprof.yaml -o memprof.profdata
+; RUN: llvm-profdata merge --memprof-version=4 memprof-no-dap.yaml -o memprof-no-dap.profdata
 
 ;; Run optimizer pass on an IR module without IR functions, and test that global
 ;; variables in the module could be annotated (i.e., no early return),
 ; RUN: opt -passes='memprof-use<profile-filename=memprof.profdata>' -memprof-annotate-static-data-prefix \
-; RUN: -debug-only=memprof -stats -S funcless-module.ll -o - 2>&1 | FileCheck %s --check-prefixes=LOG,PREFIX,STAT
+; RUN: -debug-only=memprof -stats -S funcless-module.ll -o - 2>&1 | FileCheck %s --check-prefixes=LOG,IR,STAT
 
 ;; Run optimizer pass on the IR, and check the section prefix.
 ; RUN: opt -passes='memprof-use<profile-filename=memprof.profdata>' -memprof-annotate-static-data-prefix \
-; RUN: -debug-only=memprof -stats -S input.ll -o - 2>&1 | FileCheck %s --check-prefixes=LOG,PREFIX,STAT
+; RUN: -debug-only=memprof -stats -S input.ll -o - 2>&1 | FileCheck %s --check-prefixes=LOG,IR,STAT
 
-;; Run optimizer pass without explicitly setting -memprof-annotate-static-data-prefix.
-;; The output text IR shouldn't have `section_prefix`
+;; Run memprof without providing memprof data. Test that IR has module flag
+;; `EnableDataAccessProf` as 0.
+; RUN: opt -passes='memprof-use<profile-filename=memprof-no-dap.profdata>' -memprof-annotate-static-data-prefix \
+; RUN: -debug-only=memprof -stats -S input.ll -o - 2>&1 | FileCheck %s --check-prefix=FLAG
+
+;; Run memprof without explicitly setting -memprof-annotate-static-data-prefix.
+;; The output text IR shouldn't have `section_prefix` or EnableDataAccessProf module flag.
 ; RUN: opt -passes='memprof-use<profile-filename=memprof.profdata>' \
-; RUN: -debug-only=memprof -stats -S input.ll -o - | FileCheck %s --implicit-check-not="section_prefix"
+; RUN: -debug-only=memprof -stats -S input.ll -o - | FileCheck %s --check-prefix=FLAGLESS --implicit-check-not="section_prefix"
 
 ; LOG: Skip annotating string literal .str
 ; LOG: Global variable var1 is annotated as hot
@@ -29,29 +35,33 @@
 ; LOG: Global variable var4 has explicit section name. Skip annotating.
 
 ;; String literals are not annotated.
-; PREFIX: @.str = unnamed_addr constant [5 x i8] c"abcde"
-; PREFIX-NOT: section_prefix
-; PREFIX: @var1 = global i32 123, !section_prefix !0
+; IR: @.str = unnamed_addr constant [5 x i8] c"abcde"
+; IR-NOT: section_prefix
+; IR: @var1 = global i32 123, !section_prefix !0
 
 ;; @var.llvm.125 will be canonicalized to @var2 for profile look-up.
-; PREFIX-NEXT: @var2.llvm.125 = global i64 0, !section_prefix !0
+; IR-NEXT: @var2.llvm.125 = global i64 0, !section_prefix !0
 
 ;; @bar is not seen in hot symbol or known symbol set, so it won't get a section
 ;; prefix. Test this by testing that there is no section_prefix between @bar and
 ;; @foo.
-; PREFIX-NEXT: @bar = global i16 3
-; PREFIX-NOT: !section_prefix
+; IR-NEXT: @bar = global i16 3
+; IR-NOT: !section_prefix
 
 ;; @foo is unlikely.
-; PREFIX-NEXT: @foo = global i8 2, !section_prefix !1
+; IR-NEXT: @foo = global i8 2, !section_prefix !1
+
+; IR-NEXT: @var3 = constant [2 x i32] [i32 12345, i32 6789], section "sec1"
+; IR-NEXT: @var4 = constant [1 x i64] [i64 98765] #0
 
-; PREFIX-NEXT: @var3 = constant [2 x i32] [i32 12345, i32 6789], section "sec1"
-; PREFIX-NEXT: @var4 = constant [1 x i64] [i64 98765] #0
+; IR: attributes #0 = { "rodata-section"="sec2" }
 
-; PREFIX: attributes #0 = { "rodata-section"="sec2" }
+; IR: !0 = !{!"section_prefix", !"hot"}
+; IR-NEXT: !1 = !{!"section_prefix", !"unlikely"}
+; IR-NEXT: !2 = !{i32 2, !"EnableDataAccessProf", i32 1}
 
-; PREFIX: !0 = !{!"section_prefix", !"hot"}
-; PREFIX-NEXT: !1 = !{!"section_prefix", !"unlikely"}
+; FLAG: !{i32 2, !"EnableDataAccessProf", i32 0}
+; FLAGLESS-NOT: EnableDataAccessProf
 
 ; STAT: 1 memprof - Number of global vars annotated with 'unlikely' section prefix.
 ; STAT: 2 memprof - Number of global vars with user-specified section (not annotated).
@@ -72,6 +82,24 @@ DataAccessProfiles:
     - foo
   KnownColdStrHashes: [ 999, 1001 ]
 ...
+;--- memprof-no-dap.yaml
+---
+# A memprof file with without data access profiles. The heap records are simplified
+# to pass profile parsing and don't need to match the IR.
+HeapProfileRecords:
+  - GUID:            0xdeadbeef12345678
+    AllocSites:
+      - Callstack:
+          - { Function: 0x1111111111111111, LineOffset: 11, Column: 10, IsInlineFrame: true }
+        MemInfoBlock:
+          AllocCount:      111
+          TotalSize:       222
+          TotalLifetime:   333
+          TotalLifetimeAccessDensity: 444
+    CallSites:
+      - Frames:
+        - { Function: 0x5555555555555555, LineOffset: 55, Column: 50, IsInlineFrame: true }
+...
 ;--- input.ll
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"