[lld] [llvm] [InstrProf] No linkage prefixes in IRPGO names (PR #76994)
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Thu Jan 4 11:55:47 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-pgo
Author: Ellis Hoag (ellishg)
<details>
<summary>Changes</summary>
Change the format of IRPGO counter names to `[<filepath>;]<mangled-name>` which is computed by `GlobalValue::getGlobalIdentifier()` to fix #<!-- -->74565.
In fe051934cbb0aaf25d960d7d45305135635d650b (https://reviews.llvm.org/D156569) the format of IRPGO counter names was changed to be `[<filepath>;]<linkage-name>` where `<linkage-name>` is basically `F.getName()` with some prefix, e.g., `_` or `l_` on Mach-O (yes, it is confusing that `<linkage-name>` is computed with `Mangler().getNameWithPrefix()` while `<mangled-name>` is just `F.getName()`). We discovered in #<!-- -->74565 that this causes some missed import issues on some targets and #<!-- -->74008 is a partial fix.
Since `<mangled-name>` may not match the `<linkage-name>` on some targets like Mach-O, we will need to post-process the output of `llvm-profdata order` before passing to the linker via `-order_file`.
Profiles generated after fe051934cbb0aaf25d960d7d45305135635d650b will become stale after this diff, but I think this is acceptable since that patch landed after the LLVM 18 cut which hasn't been released yet.
---
Full diff: https://github.com/llvm/llvm-project/pull/76994.diff
4 Files Affected:
- (modified) lld/test/MachO/pgo-warn-mismatch.ll (+1-1)
- (modified) llvm/lib/ProfileData/InstrProf.cpp (+18-34)
- (modified) llvm/tools/llvm-profdata/llvm-profdata.cpp (+5-1)
- (modified) llvm/unittests/ProfileData/InstrProfTest.cpp (+2-16)
``````````diff
diff --git a/lld/test/MachO/pgo-warn-mismatch.ll b/lld/test/MachO/pgo-warn-mismatch.ll
index 632adffb01fb3e..365eeaccb4b403 100644
--- a/lld/test/MachO/pgo-warn-mismatch.ll
+++ b/lld/test/MachO/pgo-warn-mismatch.ll
@@ -24,7 +24,7 @@ entry:
;--- cs.proftext
:csir
-_foo
+foo
# Func Hash:
2277602155505015273
# Num Counters:
diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
index 134a400e639c4b..08126cff7d06be 100644
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -14,7 +14,6 @@
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
@@ -27,7 +26,6 @@
#include "llvm/IR/Instruction.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
-#include "llvm/IR/Mangler.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
@@ -297,31 +295,6 @@ static StringRef getStrippedSourceFileName(const GlobalObject &GO) {
return FileName;
}
-// The PGO name has the format [<filepath>;]<linkage-name> where <filepath>; is
-// provided if linkage is local and <linkage-name> is the mangled function
-// name. The filepath is used to discriminate possibly identical function names.
-// ; is used because it is unlikely to be found in either <filepath> or
-// <linkage-name>.
-//
-// Older compilers used getPGOFuncName() which has the format
-// [<filepath>:]<function-name>. <filepath> is used to discriminate between
-// possibly identical function names when linkage is local and <function-name>
-// simply comes from F.getName(). This caused trouble for Objective-C functions
-// which commonly have :'s in their names. Also, since <function-name> is not
-// mangled, they cannot be passed to Mach-O linkers via -order_file. We still
-// need to compute this name to lookup functions from profiles built by older
-// compilers.
-static std::string
-getIRPGONameForGlobalObject(const GlobalObject &GO,
- GlobalValue::LinkageTypes Linkage,
- StringRef FileName) {
- SmallString<64> Name;
- // FIXME: Mangler's handling is kept outside of `getGlobalIdentifier` for now.
- // For more details please check issue #74565.
- Mangler().getNameWithPrefix(Name, &GO, /*CannotUsePrivateLabel=*/true);
- return GlobalValue::getGlobalIdentifier(Name, Linkage, FileName);
-}
-
static std::optional<std::string> lookupPGONameFromMetadata(MDNode *MD) {
if (MD != nullptr) {
StringRef S = cast<MDString>(MD->getOperand(0))->getString();
@@ -330,7 +303,17 @@ static std::optional<std::string> lookupPGONameFromMetadata(MDNode *MD) {
return {};
}
-// Returns the PGO object name. This function has some special handling
+// The PGO name has the format [<filepath>;]<function-name> where <filepath>; is
+// provided if linkage is local and is used to discriminate possibly identical
+// function names. ";" is used because it is unlikely to be found in either
+// <filepath> or <linkage-name>.
+//
+// Older compilers used getPGOFuncName() which has the format
+// [<filepath>:]<function-name>. This caused trouble for Objective-C functions
+// which commonly have :'s in their names. We still need to compute this name to
+// lookup functions from profiles built by older compilers.
+//
+// This function has some special handling
// when called in LTO optimization. The following only applies when calling in
// LTO passes (when \c InLTO is true): LTO's internalization privatizes many
// global linkage symbols. This happens after value profile annotation, but
@@ -347,7 +330,8 @@ static std::string getIRPGOObjectName(const GlobalObject &GO, bool InLTO,
MDNode *PGONameMetadata) {
if (!InLTO) {
auto FileName = getStrippedSourceFileName(GO);
- return getIRPGONameForGlobalObject(GO, GO.getLinkage(), FileName);
+ return GlobalValue::getGlobalIdentifier(GO.getName(), GO.getLinkage(),
+ FileName);
}
// In LTO mode (when InLTO is true), first check if there is a meta data.
@@ -357,7 +341,8 @@ static std::string getIRPGOObjectName(const GlobalObject &GO, bool InLTO,
// If there is no meta data, the function must be a global before the value
// profile annotation pass. Its current linkage may be internal if it is
// internalized in LTO mode.
- return getIRPGONameForGlobalObject(GO, GlobalValue::ExternalLinkage, "");
+ return GlobalValue::getGlobalIdentifier(GO.getName(),
+ GlobalValue::ExternalLinkage, "");
}
// Returns the IRPGO function name and does special handling when called
@@ -371,8 +356,8 @@ std::string getIRPGOFuncName(const Function &F, bool InLTO) {
// The implementation is kept for profile matching from older profiles.
// This is similar to `getIRPGOFuncName` except that this function calls
// 'getPGOFuncName' to get a name and `getIRPGOFuncName` calls
-// 'getIRPGONameForGlobalObject'. See the difference between two callees in the
-// comments of `getIRPGONameForGlobalObject`.
+// 'getIRPGOObjectName'. See the difference between two callees in the
+// comments of `getIRPGOObjectName`.
std::string getPGOFuncName(const Function &F, bool InLTO, uint64_t Version) {
if (!InLTO) {
auto FileName = getStrippedSourceFileName(F);
@@ -401,8 +386,7 @@ getParsedIRPGOFuncName(StringRef IRPGOFuncName) {
StringRef getFuncNameWithoutPrefix(StringRef PGOFuncName, StringRef FileName) {
if (FileName.empty())
return PGOFuncName;
- // Drop the file name including ':' or ';'. See getIRPGONameForGlobalObject as
- // well.
+ // Drop the file name including ':' or ';'. See getIRPGOObjectName as well.
if (PGOFuncName.starts_with(FileName))
PGOFuncName = PGOFuncName.drop_front(FileName.size() + 1);
return PGOFuncName;
diff --git a/llvm/tools/llvm-profdata/llvm-profdata.cpp b/llvm/tools/llvm-profdata/llvm-profdata.cpp
index 12b81d411cfa91..0a611d199026d8 100644
--- a/llvm/tools/llvm-profdata/llvm-profdata.cpp
+++ b/llvm/tools/llvm-profdata/llvm-profdata.cpp
@@ -3157,7 +3157,11 @@ static int order_main(int argc, const char *argv[]) {
BalancedPartitioning BP(Config);
BP.run(Nodes);
- WithColor::note() << "# Ordered " << Nodes.size() << " functions\n";
+ OS << "# Ordered " << Nodes.size() << " functions\n";
+ OS << "# Warning: Mach-O prefixes symbols with \"_\" or \"l_\" depending on "
+ "the linkage and this output does not take this into account. Some "
+ "post processing may be required before passing to the linker via "
+ "-order_file.\n";
for (auto &N : Nodes) {
auto [Filename, ParsedFuncName] =
getParsedIRPGOFuncName(Reader->getSymtab().getFuncOrVarName(N.Id));
diff --git a/llvm/unittests/ProfileData/InstrProfTest.cpp b/llvm/unittests/ProfileData/InstrProfTest.cpp
index 6a71a975fbb12d..8ffb68de7a2d20 100644
--- a/llvm/unittests/ProfileData/InstrProfTest.cpp
+++ b/llvm/unittests/ProfileData/InstrProfTest.cpp
@@ -542,22 +542,14 @@ TEST_F(InstrProfTest, test_memprof_merge) {
TEST_F(InstrProfTest, test_irpgo_function_name) {
LLVMContext Ctx;
auto M = std::make_unique<Module>("MyModule.cpp", Ctx);
- // Use Mach-O mangling so that non-private symbols get a `_` prefix.
- M->setDataLayout(DataLayout("m:o"));
auto *FTy = FunctionType::get(Type::getVoidTy(Ctx), /*isVarArg=*/false);
std::vector<std::tuple<StringRef, Function::LinkageTypes, StringRef>> Data;
- Data.emplace_back("ExternalFoo", Function::ExternalLinkage, "_ExternalFoo");
+ Data.emplace_back("ExternalFoo", Function::ExternalLinkage, "ExternalFoo");
Data.emplace_back("InternalFoo", Function::InternalLinkage,
- "MyModule.cpp;_InternalFoo");
- Data.emplace_back("PrivateFoo", Function::PrivateLinkage,
- "MyModule.cpp;l_PrivateFoo");
- Data.emplace_back("WeakODRFoo", Function::WeakODRLinkage, "_WeakODRFoo");
- // Test Objective-C symbols
+ "MyModule.cpp;InternalFoo");
Data.emplace_back("\01-[C dynamicFoo:]", Function::ExternalLinkage,
"-[C dynamicFoo:]");
- Data.emplace_back("-<C directFoo:>", Function::ExternalLinkage,
- "_-<C directFoo:>");
Data.emplace_back("\01-[C internalFoo:]", Function::InternalLinkage,
"MyModule.cpp;-[C internalFoo:]");
@@ -590,10 +582,6 @@ TEST_F(InstrProfTest, test_pgo_function_name) {
Data.emplace_back("ExternalFoo", Function::ExternalLinkage, "ExternalFoo");
Data.emplace_back("InternalFoo", Function::InternalLinkage,
"MyModule.cpp:InternalFoo");
- Data.emplace_back("PrivateFoo", Function::PrivateLinkage,
- "MyModule.cpp:PrivateFoo");
- Data.emplace_back("WeakODRFoo", Function::WeakODRLinkage, "WeakODRFoo");
- // Test Objective-C symbols
Data.emplace_back("\01-[C externalFoo:]", Function::ExternalLinkage,
"-[C externalFoo:]");
Data.emplace_back("\01-[C internalFoo:]", Function::InternalLinkage,
@@ -611,8 +599,6 @@ TEST_F(InstrProfTest, test_pgo_function_name) {
TEST_F(InstrProfTest, test_irpgo_read_deprecated_names) {
LLVMContext Ctx;
auto M = std::make_unique<Module>("MyModule.cpp", Ctx);
- // Use Mach-O mangling so that non-private symbols get a `_` prefix.
- M->setDataLayout(DataLayout("m:o"));
auto *FTy = FunctionType::get(Type::getVoidTy(Ctx), /*isVarArg=*/false);
auto *InternalFooF =
Function::Create(FTy, Function::InternalLinkage, "InternalFoo", M.get());
``````````
</details>
https://github.com/llvm/llvm-project/pull/76994
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