[clang] [llvm] [MemProf] Convert removal of memprof attrs and metadata to a pass (PR #163841)
Teresa Johnson via cfe-commits
cfe-commits at lists.llvm.org
Thu Oct 16 11:29:26 PDT 2025
https://github.com/teresajohnson created https://github.com/llvm/llvm-project/pull/163841
In preparation for a follow on fix that removes these attributes and
metadata in non-LTO pipelines, convert updateMemProfAttributes to a new
MemProfRemoveInfo pass that executes at the start of the LTO backend
pass pipelines when we don't have an index indicating that we linked
with a library support hot cold operator new.
This is largely NFC from an end user perspective but changes where the
removal can be observed, hence the test updates.
A follow on change will use the new pass for non-LTO pipelines (for
cases when the bitcode is initially matched with memprof data but we
decide to complete the compile without LTO).
>From 08d47c8f2ca515e25adf12219b7c76ff6b5b32ab Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson at google.com>
Date: Thu, 16 Oct 2025 11:23:58 -0700
Subject: [PATCH] [MemProf] Convert removal of memprof attrs and metadata to a
pass
In preparation for a follow on fix that removes these attributes and
metadata in non-LTO pipelines, convert updateMemProfAttributes to a new
MemProfRemoveInfo pass that executes at the start of the LTO backend
pass pipelines when we don't have an index indicating that we linked
with a library support hot cold operator new.
This is largely NFC from an end user perspective but changes where the
removal can be observed, hence the test updates.
A follow on change will use the new pass for non-LTO pipelines (for
cases when the bitcode is initially matched with memprof data but we
decide to complete the compile without LTO).
---
.../supports-hot-cold-new.ll | 4 +-
llvm/include/llvm/LTO/LTO.h | 6 ---
.../IPO/MemProfContextDisambiguation.h | 10 +++++
llvm/lib/LTO/LTO.cpp | 34 ----------------
llvm/lib/LTO/LTOBackend.cpp | 1 -
llvm/lib/Passes/PassBuilderPipelines.cpp | 12 ++++++
llvm/lib/Passes/PassRegistry.def | 1 +
.../IPO/MemProfContextDisambiguation.cpp | 39 +++++++++++++++++++
.../LTO/X86/memprof-supports-hot-cold-new.ll | 18 ++++-----
.../X86/memprof-supports-hot-cold-new.ll | 18 ++++-----
10 files changed, 81 insertions(+), 62 deletions(-)
diff --git a/clang/test/CodeGen/distributed-thin-lto/supports-hot-cold-new.ll b/clang/test/CodeGen/distributed-thin-lto/supports-hot-cold-new.ll
index 08c1a2946971c..9f15c803abe84 100644
--- a/clang/test/CodeGen/distributed-thin-lto/supports-hot-cold-new.ll
+++ b/clang/test/CodeGen/distributed-thin-lto/supports-hot-cold-new.ll
@@ -22,7 +22,7 @@
; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.o.thinlto.bc -save-temps=obj
-; RUN: llvm-dis %t.s.3.import.bc -o - | FileCheck %s --check-prefix=CHECK-IR
+; RUN: llvm-dis %t.s.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR
; CHECK-IR: !memprof {{.*}} !callsite
; CHECK-IR: "memprof"="cold"
@@ -42,7 +42,7 @@
; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.o.thinlto.bc -save-temps=obj
-; RUN: llvm-dis %t.s.3.import.bc -o - | FileCheck %s \
+; RUN: llvm-dis %t.s.4.opt.bc -o - | FileCheck %s \
; RUN: --implicit-check-not "!memprof" --implicit-check-not "!callsite" \
; RUN: --implicit-check-not "memprof"="cold"
diff --git a/llvm/include/llvm/LTO/LTO.h b/llvm/include/llvm/LTO/LTO.h
index 3a9a7f7c25859..000472fe9a3c4 100644
--- a/llvm/include/llvm/LTO/LTO.h
+++ b/llvm/include/llvm/LTO/LTO.h
@@ -105,12 +105,6 @@ setupStatsFile(StringRef StatsFilename);
/// ordered indices to elements in the input array.
LLVM_ABI std::vector<int> generateModulesOrdering(ArrayRef<BitcodeModule *> R);
-/// Updates MemProf attributes (and metadata) based on whether the index
-/// has recorded that we are linking with allocation libraries containing
-/// the necessary APIs for downstream transformations.
-LLVM_ABI void updateMemProfAttributes(Module &Mod,
- const ModuleSummaryIndex &Index);
-
class LTO;
struct SymbolResolution;
diff --git a/llvm/include/llvm/Transforms/IPO/MemProfContextDisambiguation.h b/llvm/include/llvm/Transforms/IPO/MemProfContextDisambiguation.h
index f2de08353f2a6..576f1eb09953a 100644
--- a/llvm/include/llvm/Transforms/IPO/MemProfContextDisambiguation.h
+++ b/llvm/include/llvm/Transforms/IPO/MemProfContextDisambiguation.h
@@ -95,6 +95,16 @@ class MemProfContextDisambiguation
function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
isPrevailing);
};
+
+/// Strips MemProf attributes and metadata. Can be invoked by the pass pipeline
+/// when we don't have an index that has recorded that we are linking with
+/// allocation libraries containing the necessary APIs for downstream
+/// transformations.
+class MemProfRemoveInfo : public PassInfoMixin<MemProfRemoveInfo> {
+public:
+ PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
+};
+
} // end namespace llvm
#endif // LLVM_TRANSFORMS_IPO_MEMPROF_CONTEXT_DISAMBIGUATION_H
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index e6544f3bafff4..aec8891eabe77 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -1257,38 +1257,6 @@ Error LTO::run(AddStreamFn AddStream, FileCache Cache) {
return Result;
}
-void lto::updateMemProfAttributes(Module &Mod,
- const ModuleSummaryIndex &Index) {
- llvm::TimeTraceScope timeScope("LTO update memprof attributes");
- if (Index.withSupportsHotColdNew())
- return;
-
- // The profile matcher applies hotness attributes directly for allocations,
- // and those will cause us to generate calls to the hot/cold interfaces
- // unconditionally. If supports-hot-cold-new was not enabled in the LTO
- // link then assume we don't want these calls (e.g. not linking with
- // the appropriate library, or otherwise trying to disable this behavior).
- for (auto &F : Mod) {
- for (auto &BB : F) {
- for (auto &I : BB) {
- auto *CI = dyn_cast<CallBase>(&I);
- if (!CI)
- continue;
- if (CI->hasFnAttr("memprof"))
- CI->removeFnAttr("memprof");
- // Strip off all memprof metadata as it is no longer needed.
- // Importantly, this avoids the addition of new memprof attributes
- // after inlining propagation.
- // TODO: If we support additional types of MemProf metadata beyond hot
- // and cold, we will need to update the metadata based on the allocator
- // APIs supported instead of completely stripping all.
- CI->setMetadata(LLVMContext::MD_memprof, nullptr);
- CI->setMetadata(LLVMContext::MD_callsite, nullptr);
- }
- }
- }
-}
-
Error LTO::runRegularLTO(AddStreamFn AddStream) {
llvm::TimeTraceScope timeScope("Run regular LTO");
LLVMContext &CombinedCtx = RegularLTO.CombinedModule->getContext();
@@ -1346,8 +1314,6 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
}
}
- updateMemProfAttributes(*RegularLTO.CombinedModule, ThinLTO.CombinedIndex);
-
bool WholeProgramVisibilityEnabledInLTO =
Conf.HasWholeProgramVisibility &&
// If validation is enabled, upgrade visibility only when all vtables
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 11a7b3221bec9..280c3d1d8dfa8 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -726,7 +726,6 @@ Error lto::thinBackend(const Config &Conf, unsigned Task, AddStreamFn AddStream,
}
// Do this after any importing so that imported code is updated.
- updateMemProfAttributes(Mod, CombinedIndex);
updatePublicTypeTestCalls(Mod, CombinedIndex.withWholeProgramVisibility());
if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index fea0d255cc91a..2d688957c952e 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1803,6 +1803,12 @@ ModulePassManager PassBuilder::buildThinLTODefaultPipeline(
OptimizationLevel Level, const ModuleSummaryIndex *ImportSummary) {
ModulePassManager MPM;
+ // If we are invoking this without a summary index noting that we are linking
+ // with a library containing the necessary APIs, remove any MemProf related
+ // attributes and metadata.
+ if (!ImportSummary || !ImportSummary->withSupportsHotColdNew())
+ MPM.addPass(MemProfRemoveInfo());
+
if (ImportSummary) {
// For ThinLTO we must apply the context disambiguation decisions early, to
// ensure we can correctly match the callsites to summary data.
@@ -1874,6 +1880,12 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
invokeFullLinkTimeOptimizationEarlyEPCallbacks(MPM, Level);
+ // If we are invoking this without a summary index noting that we are linking
+ // with a library containing the necessary APIs, remove any MemProf related
+ // attributes and metadata.
+ if (!ExportSummary || !ExportSummary->withSupportsHotColdNew())
+ MPM.addPass(MemProfRemoveInfo());
+
// Create a function that performs CFI checks for cross-DSO calls with targets
// in the current module.
MPM.addPass(CrossDSOCFIPass());
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index 1b1652555cd28..884d8daf63463 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -113,6 +113,7 @@ MODULE_PASS("pgo-force-function-attrs",
? PGOOpt->ColdOptType
: PGOOptions::ColdFuncOpt::Default))
MODULE_PASS("memprof-context-disambiguation", MemProfContextDisambiguation())
+MODULE_PASS("memprof-remove-attributes", MemProfRemoveInfo())
MODULE_PASS("memprof-module", ModuleMemProfilerPass())
MODULE_PASS("mergefunc", MergeFunctionsPass())
MODULE_PASS("metarenamer", MetaRenamerPass())
diff --git a/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp b/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
index 5066a99fa0858..894d83fa530b1 100644
--- a/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
+++ b/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
@@ -6150,3 +6150,42 @@ void MemProfContextDisambiguation::run(
IndexCallsiteContextGraph CCG(Index, isPrevailing);
CCG.process();
}
+
+// Strips MemProf attributes and metadata. Can be invoked by the pass pipeline
+// when we don't have an index that has recorded that we are linking with
+// allocation libraries containing the necessary APIs for downstream
+// transformations.
+PreservedAnalyses MemProfRemoveInfo::run(Module &M, ModuleAnalysisManager &AM) {
+ // The profile matcher applies hotness attributes directly for allocations,
+ // and those will cause us to generate calls to the hot/cold interfaces
+ // unconditionally. If supports-hot-cold-new was not enabled in the LTO
+ // link then assume we don't want these calls (e.g. not linking with
+ // the appropriate library, or otherwise trying to disable this behavior).
+ bool Changed = false;
+ for (auto &F : M) {
+ for (auto &BB : F) {
+ for (auto &I : BB) {
+ auto *CI = dyn_cast<CallBase>(&I);
+ if (!CI)
+ continue;
+ if (CI->hasFnAttr("memprof")) {
+ CI->removeFnAttr("memprof");
+ Changed = true;
+ }
+ if (!CI->hasMetadata(LLVMContext::MD_callsite)) {
+ assert(!CI->hasMetadata(LLVMContext::MD_memprof));
+ continue;
+ }
+ // Strip off all memprof metadata as it is no longer needed.
+ // Importantly, this avoids the addition of new memprof attributes
+ // after inlining propagation.
+ CI->setMetadata(LLVMContext::MD_memprof, nullptr);
+ CI->setMetadata(LLVMContext::MD_callsite, nullptr);
+ Changed = true;
+ }
+ }
+ }
+ if (!Changed)
+ return PreservedAnalyses::all();
+ return PreservedAnalyses::none();
+}
diff --git a/llvm/test/LTO/X86/memprof-supports-hot-cold-new.ll b/llvm/test/LTO/X86/memprof-supports-hot-cold-new.ll
index 3ed68e8137a35..966c66d362e88 100644
--- a/llvm/test/LTO/X86/memprof-supports-hot-cold-new.ll
+++ b/llvm/test/LTO/X86/memprof-supports-hot-cold-new.ll
@@ -13,14 +13,14 @@
; RUN: -r=%t.o,main,plx \
; RUN: -r=%t.o,_Znam, \
; RUN: -memprof-dump-ccg \
-; RUN: -save-temps \
-; RUN: -o %t.out 2>&1 | FileCheck %s --check-prefix=DUMP
-; DUMP: Callsite Context Graph:
+; RUN: -print-before=memprof-context-disambiguation \
+; RUN: -o %t.out 2>&1 | FileCheck %s --check-prefix=DUMP --check-prefix=IR
-; RUN: llvm-dis %t.out.0.0.preopt.bc -o - | FileCheck %s --check-prefix=IR
; IR: !memprof {{.*}} !callsite
; IR: "memprof"="cold"
+; DUMP: Callsite Context Graph:
+
;; Next check without -supports-hot-cold-new, we should not perform
;; context disambiguation, and we should strip memprof metadata and
;; attributes before optimization.
@@ -28,13 +28,11 @@
; RUN: -r=%t.o,main,plx \
; RUN: -r=%t.o,_Znam, \
; RUN: -memprof-dump-ccg \
-; RUN: -save-temps \
+; RUN: -print-before=memprof-context-disambiguation \
; RUN: -o %t.out 2>&1 | FileCheck %s --allow-empty \
-; RUN: --implicit-check-not "Callsite Context Graph:"
-
-; RUN: llvm-dis %t.out.0.0.preopt.bc -o - | FileCheck %s \
-; RUN: --implicit-check-not "!memprof" --implicit-check-not "!callsite" \
-; RUN: --implicit-check-not "memprof"="cold"
+; RUN: --implicit-check-not "Callsite Context Graph:" \
+; RUN: --implicit-check-not "!memprof" --implicit-check-not "!callsite" \
+; RUN: --implicit-check-not "memprof"="cold"
source_filename = "memprof-supports-hot-cold-new.ll"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/ThinLTO/X86/memprof-supports-hot-cold-new.ll b/llvm/test/ThinLTO/X86/memprof-supports-hot-cold-new.ll
index 7a4d860d8d0d9..fe2a00259f4c9 100644
--- a/llvm/test/ThinLTO/X86/memprof-supports-hot-cold-new.ll
+++ b/llvm/test/ThinLTO/X86/memprof-supports-hot-cold-new.ll
@@ -17,11 +17,12 @@
; RUN: -r=%t/foo.o,foo,plx \
; RUN: -r=%t/foo.o,_Znam, \
; RUN: -memprof-dump-ccg \
-; RUN: -save-temps \
-; RUN: -o %t.out 2>&1 | FileCheck %s --check-prefix=DUMP
+; RUN: -print-before=memprof-context-disambiguation \
+; RUN: -thinlto-threads=1 \
+; RUN: -o %t.out 2>&1 | FileCheck %s --check-prefix=DUMP --check-prefix=IR
+
; DUMP: Callsite Context Graph:
-; RUN: llvm-dis %t.out.1.3.import.bc -o - | FileCheck %s --check-prefix=IR
; IR: @main()
; IR: !memprof {{.*}} !callsite
; IR: @_Znam(i64 0) #[[ATTR:[0-9]+]]
@@ -41,13 +42,12 @@
; RUN: -r=%t/foo.o,foo,plx \
; RUN: -r=%t/foo.o,_Znam, \
; RUN: -memprof-dump-ccg \
-; RUN: -save-temps \
+; RUN: -print-before=memprof-context-disambiguation \
+; RUN: -thinlto-threads=1 \
; RUN: -o %t.out 2>&1 | FileCheck %s --allow-empty \
-; RUN: --implicit-check-not "Callsite Context Graph:"
-
-; RUN: llvm-dis %t.out.1.3.import.bc -o - | FileCheck %s \
-; RUN: --implicit-check-not "!memprof" --implicit-check-not "!callsite" \
-; RUN: --implicit-check-not "memprof"="cold"
+; RUN: --implicit-check-not "Callsite Context Graph:" \
+; RUN: --implicit-check-not "!memprof" --implicit-check-not "!callsite" \
+; RUN: --implicit-check-not "memprof"="cold"
;--- main.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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