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ltoplugin: preserve names for shared sret slots #2345

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ltoplugin: preserve names for shared sret slots #2345

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16 changes: 16 additions & 0 deletions cl/compile_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ import (
"github.com/goplus/llgo/internal/build"
"github.com/goplus/llgo/internal/buildenv"
"github.com/goplus/llgo/internal/cabi"
"github.com/goplus/llgo/internal/filecheck"
"github.com/goplus/llgo/internal/llgen"
"github.com/goplus/llgo/internal/lto"
llvmenv "github.com/goplus/llgo/xtool/env/llvm"
Expand Down Expand Up @@ -390,6 +391,21 @@ func TestBuildAndCheckSymbolsFromTestltoLTOPluginAggregateABI(t *testing.T) {
}
}

func TestBuildAndCheckSymbolsFromTestltoLTOPluginSharedSRet(t *testing.T) {
conf := testltoLTOPluginConf(t, build.ModeGen)
checkFile := filepath.Join("..", "ltoplugin", "testdata", "shared_sret.ll")
opt := filepath.Join(llvmenv.New("").BinDir(), "opt")
cmd := exec.Command(opt, "-load-pass-plugin="+conf.LTOPlugin.Path,
"-passes=llgo-lto-pre-globaldce", "-S", "-o", "-", checkFile)
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("run LTO plugin for shared sret: %v\n%s", err, out)
}
if err := filecheck.Match(checkFile, string(out)); err != nil {
t.Fatal(err)
}
}

func TestFilterEmulatorOutput(t *testing.T) {
tests := []struct {
name string
Expand Down
57 changes: 53 additions & 4 deletions ltoplugin/LLGOReflectMethodByNamePass.cpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#include "LLGOLTOPasses.h"

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ConstantFolding.h"
Expand Down Expand Up @@ -1219,6 +1220,11 @@ Value *getSRetArg(CallBase *CB) {
return nullptr;
}

Value *getSRetStorage(CallBase *CB) {
Value *SRet = getSRetArg(CB);
return SRet ? SRet->stripPointerCasts() : nullptr;
}

void addReflectMethodCheckedLoad(CallBase *CheckedLoad, StringRef GenericTypeID,
SmallPtrSetImpl<CallBase *> &SeenLoads,
SmallVectorImpl<CallBase *> &Loads) {
Expand Down Expand Up @@ -1288,7 +1294,20 @@ class LLGOLTOPreGlobalDCEPass : public PassInfoMixin<LLGOLTOPreGlobalDCEPass> {

bool Changed = false;
const DataLayout &DL = M.getDataLayout();
DenseMap<CallBase *, Value *> SRetStorageByCall;
DenseMap<Value *, SmallVector<CallBase *, 4>> CallsBySRetStorage;
for (CallBase *ReflectCall : Calls) {
Value *SRetStorage = getSRetStorage(ReflectCall);
SRetStorageByCall.insert({ReflectCall, SRetStorage});
if (SRetStorage)
CallsBySRetStorage[SRetStorage].push_back(ReflectCall);
}

SmallPtrSet<CallBase *, 16> ProcessedCalls;
for (CallBase *ReflectCall : Calls) {
if (!ProcessedCalls.insert(ReflectCall).second)
continue;

Attribute KindAttr = ReflectCall->getFnAttr(ReflectMethodByNameCallAttr);
if (!KindAttr.isStringAttribute() || ReflectCall->arg_empty())
continue;
Expand All @@ -1306,17 +1325,47 @@ class LLGOLTOPreGlobalDCEPass : public PassInfoMixin<LLGOLTOPreGlobalDCEPass> {
continue;
}

// Optimizations can leave several MethodByName calls sharing one sret
// slot. The checked-load walk starts from the slot and sees the loads for
// all of those calls. Refine them with the union of every provable name
// instead of letting the first call claim all of them. If any name is
// unknown, leave the generic markers intact so GlobalDCE remains
// conservative.
Value *SRetStorage = SRetStorageByCall.lookup(ReflectCall);
SmallVector<CallBase *, 4> SharedCalls{ReflectCall};
if (SRetStorage) {
for (CallBase *Candidate :
CallsBySRetStorage.find(SRetStorage)->second) {
if (Candidate == ReflectCall)
continue;
Attribute CandidateKind =
Candidate->getFnAttr(ReflectMethodByNameCallAttr);
if (!CandidateKind.isStringAttribute() ||
CandidateKind.getValueAsString() != Kind)
continue;
SharedCalls.push_back(Candidate);
ProcessedCalls.insert(Candidate);
}
}

SmallVector<std::string, 4> Names;
bool KnownNames = collectStringSetFromCallArgs(ReflectCall, DL, Names);
bool KnownNames = true;
// The bounded name budget applies to the combined group. Exceeding it
// leaves every generic marker intact.
for (CallBase *SharedCall : SharedCalls) {
if (!collectStringSetFromCallArgs(SharedCall, DL, Names)) {

@fennoai fennoai Bot Aug 17, 2026

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Behavior note: MaxReflectMethodNames (32) is now applied to the union of names across the whole shared group, not per call. A shared slot with several calls whose combined unique names exceed 32 will hit the cap in addName, set KnownNames=false, and refine none of them (falling back to the generic marker). This is safe/conservative, but the shared budget is a subtle change from the previous per-call limit — worth a one-line comment here so a future maintainer isn't surprised.

@zhouguangyuan0718 zhouguangyuan0718 Aug 17, 2026

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Added a comment that the bounded name budget applies to the combined shared group and that exceeding it preserves the generic markers.

KnownNames = false;
break;
}
}
if (!KnownNames || Names.empty())
continue;

SmallVector<CallBase *, 2> GenericLoads;
SmallPtrSet<CallBase *, 4> SeenLoads;
SmallPtrSet<Value *, 16> SeenValues;
collectSRetReflectMethodCheckedLoads(getSRetArg(ReflectCall),
GenericTypeID, SeenValues, SeenLoads,
GenericLoads);
collectSRetReflectMethodCheckedLoads(SRetStorage, GenericTypeID,
SeenValues, SeenLoads, GenericLoads);
for (CallBase *GenericLoad : GenericLoads) {
insertMethodNameChecks(GenericLoad, Names, Prefix);
if (!eraseGenericCheckedLoad(GenericLoad))
Expand Down
104 changes: 104 additions & 0 deletions ltoplugin/testdata/shared_sret.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,104 @@
; RUN: opt -load-pass-plugin=%plugin -passes=llgo-lto-pre-globaldce -S %s | FileCheck %s

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"

%reflect.Value = type { ptr }

@query = private unnamed_addr constant [5 x i8] c"Query"
@mutation = private unnamed_addr constant [8 x i8] c"Mutation"
@subscription = private unnamed_addr constant [12 x i8] c"Subscription"

declare void @reflect.Value.MethodByName(ptr sret(%reflect.Value), ptr, i64)
declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)
declare void @llvm.assume(i1)

define void @shared_sret(ptr %receiver) {
entry:
%ret = alloca %reflect.Value
call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @query, i64 5) #0
%query.fn = load ptr, ptr %ret
%query.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %query.fn, i32 0, metadata !"go.method.value.reflect")
%query.ok = extractvalue { ptr, i1 } %query.checked, 1
call void @llvm.assume(i1 %query.ok)

call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @mutation, i64 8) #0
%mutation.fn = load ptr, ptr %ret
%mutation.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %mutation.fn, i32 0, metadata !"go.method.value.reflect")
%mutation.ok = extractvalue { ptr, i1 } %mutation.checked, 1
call void @llvm.assume(i1 %mutation.ok)

call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @subscription, i64 12) #0
%subscription.fn = load ptr, ptr %ret
%subscription.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %subscription.fn, i32 0, metadata !"go.method.value.reflect")
%subscription.ok = extractvalue { ptr, i1 } %subscription.checked, 1
call void @llvm.assume(i1 %subscription.ok)
ret void
}

define void @shared_sret_unknown(ptr %receiver, ptr %dynamic.name, i64 %dynamic.len) {
entry:
%ret = alloca %reflect.Value
call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @query, i64 5) #0
%query.fn = load ptr, ptr %ret
%query.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %query.fn, i32 0, metadata !"go.method.value.reflect")
%query.ok = extractvalue { ptr, i1 } %query.checked, 1
call void @llvm.assume(i1 %query.ok)

call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" %dynamic.name, i64 %dynamic.len) #0
%dynamic.fn = load ptr, ptr %ret
%dynamic.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %dynamic.fn, i32 0, metadata !"go.method.value.reflect")
%dynamic.ok = extractvalue { ptr, i1 } %dynamic.checked, 1
call void @llvm.assume(i1 %dynamic.ok)
ret void
}

define void @shared_sret_duplicate(ptr %receiver) {
entry:
%ret = alloca %reflect.Value
call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @query, i64 5) #0
%first.fn = load ptr, ptr %ret
%first.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %first.fn, i32 0, metadata !"go.method.value.reflect")
%first.ok = extractvalue { ptr, i1 } %first.checked, 1
call void @llvm.assume(i1 %first.ok)

call void @reflect.Value.MethodByName(ptr sret(%reflect.Value) %ret, ptr "llgo.reflect.methodbyname.name"="1" @query, i64 5) #0
%second.fn = load ptr, ptr %ret
%second.checked = call { ptr, i1 } @llvm.type.checked.load(ptr %second.fn, i32 0, metadata !"go.method.value.reflect")
%second.ok = extractvalue { ptr, i1 } %second.checked, 1
call void @llvm.assume(i1 %second.ok)
ret void
}

; CHECK-LABEL: define void @shared_sret(
; CHECK: call void @reflect.Value.MethodByName({{.*}}@query
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Query")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Mutation")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Subscription")
; CHECK: call void @reflect.Value.MethodByName({{.*}}@mutation
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Query")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Mutation")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Subscription")
; CHECK: call void @reflect.Value.MethodByName({{.*}}@subscription
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Query")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Mutation")
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Subscription")
; CHECK-NOT: !"go.method.value.reflect"

; CHECK-LABEL: define void @shared_sret_unknown(
; CHECK-NOT: !"go.method.value.reflect.Query"
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect")
; CHECK-NOT: !"go.method.value.reflect.Query"
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect")
; CHECK-NOT: !"go.method.value.reflect.Query"
; CHECK: ret void

; CHECK-LABEL: define void @shared_sret_duplicate(
; CHECK: call void @reflect.Value.MethodByName({{.*}}@query
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Query")
; CHECK-NOT: !"go.method.value.reflect.Query"
; CHECK: call void @reflect.Value.MethodByName({{.*}}@query
; CHECK: @llvm.type.checked.load({{.*}}!"go.method.value.reflect.Query")
; CHECK-NOT: !"go.method.value.reflect.Query"
; CHECK: ret void

attributes #0 = { "llgo.reflect.methodbyname"="value" }
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