[llvm] [MemProf] Strip callsite metadata when inlining an unprofiled callsite (PR #110998)

[Teresa Johnson via llvm-commits]

https://github.com/teresajohnson created https://github.com/llvm/llvm-project/pull/110998

We weren't flagging inlined callee functions with callsite but not
memprof metadata correctly, leading to the callsite metadata not being
stripped when that function was inlined into a callsite that didn't
itself have callsite metadata.

In practice, this meant that we went into the LTO link with many more
calls than necessary having callsite metadata / summary records, which
in turn made the graph larger than necessary.

Fixing this oversight resulted in huge reductions in the thin link of a
large target:
99% fewer duplicated context ids (recall we have to duplicate when
callsites containing the same stack ids are in different functions)
71% fewer graph edges
17% fewer graph nodes
13% fewer functions cloned
44% smaller peak memory
47% smaller time


>From 078ac710d2f514a768cb70392221f476b120f7a4 Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson at google.com>
Date: Thu, 3 Oct 2024 07:04:09 -0700
Subject: [PATCH] [MemProf] Strip callsite metadata when inlining an unprofiled
 callsite

We weren't flagging inlined callee functions with callsite but not
memprof metadata correctly, leading to the callsite metadata not being
stripped when that function was inlined into a callsite that didn't
itself have callsite metadata.

In practice, this meant that we went into the LTO link with many more
calls than necessary having callsite metadata / summary records, which
in turn made the graph larger than necessary.

Fixing this oversight resulted in huge reductions in the thin link of a
large target:
99% fewer duplicated context ids (recall we have to duplicate when
callsites containing the same stack ids are in different functions)
71% fewer graph edges
17% fewer graph nodes
13% fewer functions cloned
44% smaller peak memory
47% smaller time
---
 llvm/lib/Transforms/Utils/CloneFunction.cpp    | 2 ++
 llvm/test/Transforms/Inline/memprof_inline2.ll | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index dc9ca1423f3e79..fc03643e3542cc 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -70,6 +70,7 @@ BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
     if (isa<CallInst>(I) && !I.isDebugOrPseudoInst()) {
       hasCalls = true;
       hasMemProfMetadata |= I.hasMetadata(LLVMContext::MD_memprof);
+      hasMemProfMetadata |= I.hasMetadata(LLVMContext::MD_callsite);
     }
     if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
       if (!AI->isStaticAlloca()) {
@@ -556,6 +557,7 @@ void PruningFunctionCloner::CloneBlock(
     if (isa<CallInst>(II) && !II->isDebugOrPseudoInst()) {
       hasCalls = true;
       hasMemProfMetadata |= II->hasMetadata(LLVMContext::MD_memprof);
+      hasMemProfMetadata |= II->hasMetadata(LLVMContext::MD_callsite);
     }
 
     CloneDbgRecordsToHere(NewInst, II);
diff --git a/llvm/test/Transforms/Inline/memprof_inline2.ll b/llvm/test/Transforms/Inline/memprof_inline2.ll
index 625971c5fa37f6..21448f142ed079 100644
--- a/llvm/test/Transforms/Inline/memprof_inline2.ll
+++ b/llvm/test/Transforms/Inline/memprof_inline2.ll
@@ -90,10 +90,18 @@ entry:
 ; CHECK-LABEL: define dso_local noundef ptr @notprofiled
 define dso_local noundef ptr @notprofiled() #0 !dbg !66 {
 entry:
+  ;; When foo is inlined, both the memprof and callsite metadata should be
+  ;; stripped from the inlined call to new, as there is no callsite metadata on
+  ;; the call.
   ; CHECK: call {{.*}} @_Znam
   ; CHECK-NOT: !memprof
   ; CHECK-NOT: !callsite
   %call = call noundef ptr @_Z3foov(), !dbg !67
+  ;; When baz is inlined, the callsite metadata should be stripped from the
+  ;; inlined call to foo2, as there is no callsite metadata on the call.
+  ; CHECK: call {{.*}} @_Z4foo2v
+  ; CHECK-NOT: !callsite
+  %call2 = call noundef ptr @_Z3bazv()
   ; CHECK-NEXT: ret
   ret ptr %call, !dbg !68
 }