[llvm-branch-commits] [llvm] [nfc][StaticDataLayout] Factor out helper functions for section prefix eligibility (PR #162348)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Mingming Liu (mingmingl-llvm)

<details>
<summary>Changes</summary>

This change introduces new helper functions to check if a global variable is eligible for section prefix annotation.

This shared logic will be used by both MemProfUse and StaticDataSplitter to avoid annotating ineligible variables.



---
Full diff: https://github.com/llvm/llvm-project/pull/162348.diff


4 Files Affected:

- (modified) llvm/include/llvm/Analysis/StaticDataProfileInfo.h (+18) 
- (modified) llvm/lib/Analysis/StaticDataProfileInfo.cpp (+37) 
- (modified) llvm/lib/CodeGen/StaticDataAnnotator.cpp (+1-1) 
- (modified) llvm/lib/Transforms/Instrumentation/MemProfUse.cpp (+8-22) 


``````````diff
diff --git a/llvm/include/llvm/Analysis/StaticDataProfileInfo.h b/llvm/include/llvm/Analysis/StaticDataProfileInfo.h
index fa21eba1377df..f06e7ceaa74ce 100644
--- a/llvm/include/llvm/Analysis/StaticDataProfileInfo.h
+++ b/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 {
diff --git a/llvm/lib/Analysis/StaticDataProfileInfo.cpp b/llvm/lib/Analysis/StaticDataProfileInfo.cpp
index b036b2dde770e..ff4582ca7eeb1 100644
--- a/llvm/lib/Analysis/StaticDataProfileInfo.cpp
+++ b/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) {
diff --git a/llvm/lib/CodeGen/StaticDataAnnotator.cpp b/llvm/lib/CodeGen/StaticDataAnnotator.cpp
index 53a9ab4dbda02..9b737751c4a98 100644
--- a/llvm/lib/CodeGen/StaticDataAnnotator.cpp
+++ b/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,
diff --git a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp b/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
index d86fcf268ce4f..ca2af1a9534d3 100644
--- a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
+++ b/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"
@@ -775,23 +776,6 @@ 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())
@@ -817,13 +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;
     }
 
@@ -833,7 +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;
     }

``````````

</details>


https://github.com/llvm/llvm-project/pull/162348