[llvm] [IR]Support set/read/update the section prefix for global objects (PR #125757)
Mingming Liu via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 5 14:23:09 PST 2025
https://github.com/mingmingl-llvm updated https://github.com/llvm/llvm-project/pull/125757
>From 0b9dc8db4a66b05cb15b9d1cbe5fd38f63e6c0dd Mon Sep 17 00:00:00 2001
From: mingmingl <mingmingl at google.com>
Date: Tue, 4 Feb 2025 11:50:32 -0800
Subject: [PATCH 1/2] [IR]Support set/read/update the section prefix for global
objects
---
llvm/include/llvm/IR/Function.h | 6 -----
llvm/include/llvm/IR/GlobalObject.h | 11 ++++++++
llvm/include/llvm/IR/MDBuilder.h | 4 +--
.../CodeGen/TargetLoweringObjectFileImpl.cpp | 5 ++++
llvm/lib/IR/Function.cpp | 16 -----------
llvm/lib/IR/Globals.cpp | 19 +++++++++++++
llvm/lib/IR/MDBuilder.cpp | 6 ++---
llvm/test/CodeGen/X86/data-section-prefix.ll | 27 +++++++++++++++++++
.../CodeGenPrepare/X86/section-samplepgo.ll | 4 +--
.../Transforms/CodeGenPrepare/X86/section.ll | 4 +--
.../Transforms/HotColdSplit/coldentrycount.ll | 4 +--
.../section-accurate-samplepgo.ll | 6 ++---
12 files changed, 76 insertions(+), 36 deletions(-)
create mode 100644 llvm/test/CodeGen/X86/data-section-prefix.ll
diff --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
index fcd5396ccfdbc8..29041688124bc2 100644
--- 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
index 08edc13d81f880..bb50c39813e140 100644
--- 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
index e02ec8f5a3d8bb..ce4e1da656049d 100644
--- 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
index 3c2c7c8c9fed69..6cbc4b9776a1b0 100644
--- 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
index e6f0d64d071ba6..5666f0a53866fd 100644
--- 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
index db5e1cb57b1bab..148f8e26535d2e 100644
--- 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 +287,24 @@ 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));
+}
+
+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
index 26c8ab9fc36c85..b6aa8844a7eafa 100644
--- 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
new file mode 100644
index 00000000000000..4812fc70758fbc
--- /dev/null
+++ 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", at progbits,unique,1
+; ELF-NOUNIQ: .section .data,"aw", at progbits,unique,2
+; ELF-NOUNIQ: .section .bss.unlikely.,"aw", at nobits,unique,3
+; ELF-NOUNIQ: .section .bss,"aw", at 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
+
+ at foo = global i32 1, !section_prefix !0
+ at bar = global i32 2
+ at baz = global i32 0, !section_prefix !1
+ at 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
index 58af88d8cf3653..48d02e5cebc69c 100644
--- 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
index 6dad1122e42945..4baa0b5baa4be5 100644
--- 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
index 6e5ef1aa253921..1e8825e651ec4c 100644
--- 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
index ef2ddbc33cee4c..af4b875818f6fe 100644
--- 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}
>From aa17d193860f072e3ab4e73db08cdbf1d94d5680 Mon Sep 17 00:00:00 2001
From: mingmingl <mingmingl at google.com>
Date: Wed, 5 Feb 2025 13:24:55 -0800
Subject: [PATCH 2/2] Implement GlobalObject::updateSectionPrefix and add a
unit test
---
llvm/lib/IR/Globals.cpp | 11 +++++
llvm/unittests/IR/CMakeLists.txt | 1 +
llvm/unittests/IR/GlobalObjectTest.cpp | 56 ++++++++++++++++++++++++++
3 files changed, 68 insertions(+)
create mode 100644 llvm/unittests/IR/GlobalObjectTest.cpp
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 148f8e26535d2e..884089262e4659 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -293,6 +293,17 @@ void GlobalObject::setSectionPrefix(StringRef 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 =
diff --git a/llvm/unittests/IR/CMakeLists.txt b/llvm/unittests/IR/CMakeLists.txt
index bea6b1b46f5732..edb7381fd8faf3 100644
--- 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
new file mode 100644
index 00000000000000..0c67fc61b7d5a4
--- /dev/null
+++ 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"(
+ at foo = global i32 1, !section_prefix !0
+ at bar = global i32 2
+ at 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");
+}
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