llvm · mingmingl-llvm · Feb 6, 2025 · Feb 4, 2025 · Feb 5, 2025 · Feb 5, 2025
diff --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
@@ -346,12 +346,6 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   /// sample PGO, to enable the same inlines as the profiled optimized binary.
   DenseSet<GlobalValue::GUID> getImportGUIDs() const;
 
-  /// Set the section prefix for this function.
-  void setSectionPrefix(StringRef Prefix);
-
-  /// Get the section prefix for this function.
-  std::optional<StringRef> getSectionPrefix() const;
-
   /// hasGC/getGC/setGC/clearGC - The name of the garbage collection algorithm
   ///                             to use during code generation.
   bool hasGC() const {

diff --git a/llvm/include/llvm/IR/GlobalObject.h b/llvm/include/llvm/IR/GlobalObject.h
@@ -124,6 +124,17 @@ class GlobalObject : public GlobalValue {
   /// appropriate default object file section.
   void setSection(StringRef S);
 
+  /// Set the section prefix for this global object.
+  void setSectionPrefix(StringRef Prefix);
+
+  /// Update the section prefix, unless the existing prefix is the same as
+  /// `KeepPrefix`.
+  void updateSectionPrefix(StringRef Prefix,
+                           std::optional<StringRef> KeepPrefix = std::nullopt);
+
+  /// Get the section prefix for this global object.
+  std::optional<StringRef> getSectionPrefix() const;
+
   bool hasComdat() const { return getComdat() != nullptr; }
   const Comdat *getComdat() const { return ObjComdat; }
   Comdat *getComdat() { return ObjComdat; }

diff --git a/llvm/include/llvm/IR/MDBuilder.h b/llvm/include/llvm/IR/MDBuilder.h
@@ -89,8 +89,8 @@ class MDBuilder {
   MDNode *createFunctionEntryCount(uint64_t Count, bool Synthetic,
                                    const DenseSet<GlobalValue::GUID> *Imports);
 
-  /// Return metadata containing the section prefix for a function.
-  MDNode *createFunctionSectionPrefix(StringRef Prefix);
+  /// Return metadata containing the section prefix for a global object.
+  MDNode *createGlobalObjectSectionPrefix(StringRef Prefix);
 
   /// Return metadata containing the pseudo probe descriptor for a function.
   MDNode *createPseudoProbeDesc(uint64_t GUID, uint64_t Hash, StringRef FName);

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -687,6 +687,11 @@ getELFSectionNameForGlobal(const GlobalObject *GO, SectionKind Kind,
       raw_svector_ostream(Name) << '.' << *Prefix;
       HasPrefix = true;
     }
+  } else if (const auto *GV = dyn_cast<GlobalVariable>(GO)) {
+    if (std::optional<StringRef> Prefix = GV->getSectionPrefix()) {
+      raw_svector_ostream(Name) << '.' << *Prefix;
+      HasPrefix = true;
+    }
   }
 
   if (UniqueSectionName) {

diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
@@ -1164,22 +1164,6 @@ DenseSet<GlobalValue::GUID> Function::getImportGUIDs() const {
   return R;
 }
 
-void Function::setSectionPrefix(StringRef Prefix) {
-  MDBuilder MDB(getContext());
-  setMetadata(LLVMContext::MD_section_prefix,
-              MDB.createFunctionSectionPrefix(Prefix));
-}
-
-std::optional<StringRef> Function::getSectionPrefix() const {
-  if (MDNode *MD = getMetadata(LLVMContext::MD_section_prefix)) {
-    assert(cast<MDString>(MD->getOperand(0))->getString() ==
-               "function_section_prefix" &&
-           "Metadata not match");
-    return cast<MDString>(MD->getOperand(1))->getString();
-  }
-  return std::nullopt;
-}
-
 bool Function::nullPointerIsDefined() const {
   return hasFnAttribute(Attribute::NullPointerIsValid);
 }

diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -286,6 +287,35 @@ void GlobalObject::setSection(StringRef S) {
   setGlobalObjectFlag(HasSectionHashEntryBit, !S.empty());
 }
 
+void GlobalObject::setSectionPrefix(StringRef Prefix) {
+  MDBuilder MDB(getContext());
+  setMetadata(LLVMContext::MD_section_prefix,
+              MDB.createGlobalObjectSectionPrefix(Prefix));
+}
+
+void GlobalObject::updateSectionPrefix(StringRef Prefix,
+                                       std::optional<StringRef> KeepPrefix) {
+  auto SectionPrefix = getSectionPrefix();
+  if (SectionPrefix && (*SectionPrefix == Prefix ||
+                        (KeepPrefix && *SectionPrefix == *KeepPrefix)))
+    return;
+
+  setSectionPrefix(Prefix);
+  return;
+}
+
+std::optional<StringRef> GlobalObject::getSectionPrefix() const {
+  if (MDNode *MD = getMetadata(LLVMContext::MD_section_prefix)) {
+    [[maybe_unused]] StringRef MDName =
+        cast<MDString>(MD->getOperand(0))->getString();
+    assert((MDName == "section_prefix" ||
+            (isa<Function>(this) && MDName == "function_section_prefix")) &&
+           "Metadata not match");
+    return cast<MDString>(MD->getOperand(1))->getString();
+  }
+  return std::nullopt;
+}
+
 bool GlobalValue::isNobuiltinFnDef() const {
   const Function *F = dyn_cast<Function>(this);
   if (!F || F->empty())

diff --git a/llvm/lib/IR/MDBuilder.cpp b/llvm/lib/IR/MDBuilder.cpp
@@ -87,9 +87,9 @@ MDNode *MDBuilder::createFunctionEntryCount(
   return MDNode::get(Context, Ops);
 }
 
-MDNode *MDBuilder::createFunctionSectionPrefix(StringRef Prefix) {
-  return MDNode::get(
-      Context, {createString("function_section_prefix"), createString(Prefix)});
+MDNode *MDBuilder::createGlobalObjectSectionPrefix(StringRef Prefix) {
+  return MDNode::get(Context,
+                     {createString("section_prefix"), createString(Prefix)});
 }
 
 MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {

diff --git a/llvm/test/CodeGen/X86/data-section-prefix.ll b/llvm/test/CodeGen/X86/data-section-prefix.ll
@@ -0,0 +1,27 @@
+; RUN: llc -mtriple x86_64-linux-gnu -data-sections %s -o - | FileCheck %s --check-prefix=ELF
+; RUN: llc -mtriple x86_64-linux-gnu -unique-section-names=0 -data-sections %s -o - | FileCheck %s --check-prefix=ELF-NOUNIQ
+
+; RUN: llc -mtriple x86_64-windows-msvc -data-sections %s -o - | FileCheck %s --check-prefix=COFF-MSVC
+
+; ELF: .section .data.hot.foo,
+; ELF: .section .data.bar,
+; ELF: .section .bss.unlikely.baz,
+; ELF: .section .bss.quz,
+
+; ELF-NOUNIQ: .section    .data.hot.,"aw",@progbits,unique,1
+; ELF-NOUNIQ: .section    .data,"aw",@progbits,unique,2
+; ELF-NOUNIQ: .section    .bss.unlikely.,"aw",@nobits,unique,3
+; ELF-NOUNIQ: .section    .bss,"aw",@nobits,unique,4
+
+; COFF-MSVC: .section .data,"dw",one_only,foo
+; COFF-MSVC: .section .data,"dw",one_only,bar
+; COFF-MSVC: .section .bss,"bw",one_only,baz
+; COFF-MSVC: .section .bss,"bw",one_only,quz
+
+@foo = global i32 1, !section_prefix !0
+@bar = global i32 2
+@baz = global i32 0, !section_prefix !1
+@quz = global i32 0
+
+!0 = !{!"section_prefix", !"hot"}
+!1 = !{!"section_prefix", !"unlikely"}
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/section-samplepgo.ll b/llvm/test/Transforms/CodeGenPrepare/X86/section-samplepgo.ll
@@ -34,8 +34,8 @@ define void @cold_func() !prof !16 {
   ret void
 }
 
-; CHECK: ![[HOT_ID]] = !{!"function_section_prefix", !"hot"}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[HOT_ID]] = !{!"section_prefix", !"hot"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}

diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/section.ll b/llvm/test/Transforms/CodeGenPrepare/X86/section.ll
@@ -66,8 +66,8 @@ define void @cold_func3() !prof !16 {
   ret void
 }
 
-; CHECK: ![[HOT_ID]] = !{!"function_section_prefix", !"hot"}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[HOT_ID]] = !{!"section_prefix", !"hot"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}

diff --git a/llvm/test/Transforms/HotColdSplit/coldentrycount.ll b/llvm/test/Transforms/HotColdSplit/coldentrycount.ll
@@ -27,9 +27,9 @@ declare void @sink() cold
 ; CHECK: define {{.*}} @fun.cold.1{{.*}} ![[PROF:[0-9]+]] {{.*}}section_prefix ![[UNLIKELY:[0-9]+]]
 
 ; CHECK: ![[HOTPROF]] = !{!"function_entry_count", i64 100}
-; CHECK: ![[LIKELY]] = !{!"function_section_prefix", !"hot"}
+; CHECK: ![[LIKELY]] = !{!"section_prefix", !"hot"}
 ; CHECK: ![[PROF]] = !{!"function_entry_count", i64 0}
-; CHECK: ![[UNLIKELY]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[UNLIKELY]] = !{!"section_prefix", !"unlikely"}
 
 !llvm.module.flags = !{!0}
 !0 = !{i32 1, !"ProfileSummary", !1}

diff --git a/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll b/llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll
@@ -36,11 +36,11 @@ attributes #1 = { "use-sample-profile" }
 
 ; CHECK: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
 ; CHECK: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 ; UNKNOWN: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
-; UNKNOWN: ![[UNKNOWN_ID]] = !{!"function_section_prefix", !"unknown"}
+; UNKNOWN: ![[UNKNOWN_ID]] = !{!"section_prefix", !"unknown"}
 ; ACCURATE: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
-; ACCURATE: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; ACCURATE: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}

diff --git a/llvm/unittests/IR/CMakeLists.txt b/llvm/unittests/IR/CMakeLists.txt
@@ -28,6 +28,7 @@ add_llvm_unittest(IRTests
   DominatorTreeBatchUpdatesTest.cpp
   DroppedVariableStatsIRTest.cpp
   FunctionTest.cpp
+  GlobalObjectTest.cpp
   PassBuilderCallbacksTest.cpp
   IRBuilderTest.cpp
   InstructionsTest.cpp

diff --git a/llvm/unittests/IR/GlobalObjectTest.cpp b/llvm/unittests/IR/GlobalObjectTest.cpp
@@ -0,0 +1,56 @@
+//===- GlobalObjectTest.cpp - Global Object unit tests
+//-----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-c/Core.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+using namespace llvm;
+
+namespace {
+
+static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
+  if (!Mod)
+    Err.print("GlobalObjectTest", errs());
+  return Mod;
+}
+
+} // namespace
+
+TEST(GlobalObjectTest, updateSectionPrefix) {
+  LLVMContext C;
+
+  std::unique_ptr<Module> M = parseIR(C, R"(
+@foo = global i32 1, !section_prefix !0
+@bar = global i32 2
+@baz = global i32 0, !section_prefix !1
+
+!0 = !{!"section_prefix", !"hot"}
+!1 = !{!"section_prefix", !"unlikely"}
+)");
+
+  GlobalVariable *Foo = M->getGlobalVariable("foo");
+  EXPECT_EQ(Foo->getSectionPrefix(), "hot");
+  Foo->updateSectionPrefix("unlikely", std::make_optional(StringRef("hot")));
+  EXPECT_EQ(Foo->getSectionPrefix(), "hot");
+
+  GlobalVariable *Bar = M->getGlobalVariable("bar");
+  EXPECT_EQ(Bar->getSectionPrefix(), std::nullopt);
+  Bar->setSectionPrefix("unlikely");
+  EXPECT_EQ(Bar->getSectionPrefix(), "unlikely");
+
+  GlobalVariable *Baz = M->getGlobalVariable("baz");
+  EXPECT_EQ(Baz->getSectionPrefix(), "unlikely");
+  Baz->updateSectionPrefix("hot");
+  EXPECT_EQ(Baz->getSectionPrefix(), "hot");
+}