cmd/compile: separate entry argument maps from stack growth

.github/workflows/goallc.yml

@@ -25,8 +25,8 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  PINNED_LLVM_RELEASE: goallc-llvm23.1.0-20260814T092516Z
-  PINNED_LLVM_REVISION: 3710742685729c697378ab13a456484e5693aba9
+  PINNED_LLVM_RELEASE: goallc-llvm23.1.0-20260815T075241Z
+  PINNED_LLVM_REVISION: 9bd4c90aca1584de810fd081bc1fd6a0cce602dd
 
 jobs:
   llvm-payload:

doc/goallc-llvm-goobj.md

@@ -171,10 +171,10 @@ use 的 local 不生成 LLVM 栈槽，避免无意义地增大 frame。
 
 GoObj stack growth、SP 恢复和当前 stack-map 路径只支持编译期固定 frame。
 因此 amd64 和 arm64 GoObj target 对 variable-sized `alloca` 都确定性报错，
-不能把动态栈分配交给 LLVM 通用 lowering。当前 GoObj writer 的 args/locals
-pointer maps 仍为空；本实现只保证现有固定栈槽的 dominance、frame placement
-和 stack-growth 约束，不代表已经支持完整 precise-GC stack maps、goroutine、
-defer 或 panic unwind。
+不能把动态栈分配交给 LLVM 通用 lowering。当前 GoObj writer 已为所有 GoObj Go
+函数生成类型推导的入口 ArgsPointerMaps，并为已支持的普通 statepoint 和固定
+`alloca` 生成 LocalsPointerMaps；这仍不代表已经支持完整 precise-GC stack maps、
+goroutine、defer 或 panic unwind。
 
 对应回归包括：
 
@@ -273,9 +273,10 @@ pass plugin 默认从 `llc` 所属 LLVM payload 的
 wrapper 覆盖的 compile action 重新编译。
 
 插件的功能性源码和测试位于 Go 仓库
-`src/cmd/llvmplugin`，不放入 LLVM 源码树。LLVM 只提供通用的
-`-load-pass-plugin` 和 pre-codegen callback；GoALLC statepoint rewrite 及其
-pass 顺序都应继续在这个 Go-owned 工程中实现。当前
+`src/cmd/llvmplugin`，不放入 LLVM 源码树。LLVM 提供通用的
+`-load-pass-plugin`、pre-codegen callback，以及 GoObj 对 Machine StackMaps
+的对象格式适配；GoALLC statepoint rewrite 及其 pass 顺序都应继续在这个
+Go-owned 工程中实现。当前
 `runPreCodeGenPipeline` 调用 Go-owned statepoint pass：它对 Go ABI 函数执行
 CFG 逆向数据流活跃性分析，为普通调用分配稳定 callsite ID，生成
 `gc.statepoint` / `gc.relocate`，并识别 `gc-leaf-function`。受管指针分类当前
@@ -285,21 +286,21 @@ aggregate、`invoke`、`musttail` 和非 leaf inline asm fail closed。未来
 compile 进程内集成 LLVM 时直接复用该 core 入口，不经过 plugin adapter。
 
 机器位置不通过修改 LLVM 通用 `StackMaps.cpp` 截获。SSA→LLVM IR 前端为 Go ABI
-函数声明 `gc "goallc"` 和 `go-stack-growth-statepoint`，插件只负责注册对应的
-GC strategy 与 `GCMetadataPrinter::emitStackMaps`，并消费这些前端标记。在
+函数声明 `gc "goallc"`；GoObj Go 函数默认采用原生 Go 的可扩栈策略，只有
+`go-nosplit`、`go-systemstack` 这样的例外策略需要额外属性。插件负责注册对应的
+GC strategy、执行 statepoint rewrite 并消费这些前端标记。在 LLVM GoObj
 AsmPrinter 模块收尾阶段
 读取标准 `FnInfos/CSInfos`，跳过 statepoint 的 CC、flags 和 deopt 前缀后，把
 原始 GC locations 写入 MCContext。GoObj writer 在最终 layout 后完成 SP
 校验、`Direct`/`Indirect` 解释、LocalsPointerMaps 和 PCDATA_StackMapIndex
-编码。GoALLC 要求 StackMaps 记录 CALL 起点；map 从 CALL 开始。前端添加的
-`go-stack-growth-statepoint` 属性使 LLVM 在 PEI 阶段把
-`runtime.morestack` 调用生成为物理 MIR `STATEPOINT`。其 deopt 和 GC alloca
-区为空，GC pointer 区则记录类型推导出的入口参数 home。它从 morestack CALL
-起点选择入口 ArgsPointerMaps 和空 locals bitmap，因此普通调用与栈增长调用
-走同一 Machine StackMaps 链路，且不依赖 return PC 反推调用范围。已有
-Machine `STATEPOINT` 但缺少该前端属性时，
-LLVM target lowering 会 fail closed；不再使用 slow-path reset label 兼容普通
-morestack CALL。GoObj 先写索引 0 的
+编码。GoALLC 要求 StackMaps 记录 CALL 起点；map 从 CALL 开始。LLVM target
+formal lowering 为每个 GoObj Go 函数推导入口参数 home，并用一个独立、零字节的
+`EntryArgsStackMapID` 表达函数级 ArgsPointerMaps；该记录不是调用点，不生成
+PCDATA。非 nosplit 函数在 PEI 阶段额外把 `runtime.morestack` 调用生成为物理、
+root-free 的 `StackGrowthStatepointID`，从 CALL 起点选择入口 ArgsPointerMaps 和
+空 locals bitmap。nosplit 函数不得包含这个 statepoint。这样普通调用与栈增长
+调用仍走同一 Machine StackMaps 链路，且不依赖 return PC 反推调用范围，同时
+函数级入口图不再伪装成 morestack 调用。GoObj 先写索引 0 的
 `PCDATA_UnsafePoint`（当前恒为 safe 的 `-1`），再写索引 1 的
 `PCDATA_StackMapIndex`；不能只写后一张表，否则 linker 会把它误认成索引 0。
 `Direct SP+offset` 是栈地址本身，不表示该 slot 存有 pointer，因此不会设置

src/cmd/compile/internal/ssa/ssa2llvm.go

@@ -70,7 +70,8 @@ const goABI0SymbolSuffix = "<ABI0>"
 const goResultsTupleAttr = "go_results_tuple"
 const goGCStrategy = "goallc"
 const goGCLeafFunctionAttr = "gc-leaf-function"
-const goStackGrowthStatepointAttr = "go-stack-growth-statepoint"
+const goNoSplitAttr = "go-nosplit"
+const goSystemStackAttr = "go-systemstack"
 const goAsyncUnsafeAttr = "go-async-unsafe"
 const goWriteBarrierIntrinsic = "llvm.go.gc.write.barrier"
 const goDeferEdgeIntrinsic = "llvm.go.defer.edge"
@@ -3087,10 +3088,20 @@ func LLVMCompile(f *Func) {
 		}
 	}
 	FCtxt.LF.AddFunctionAttr(GlobalCtxt.CreateStringAttribute(goAsyncUnsafeAttr, ""))
-	// TODO(goallc): Once LLVM lowering propagates the compiler's precise
-	// morestack policy, attach this only to functions whose prologue can grow
-	// the Go stack.
-	FCtxt.LF.AddFunctionAttr(GlobalCtxt.CreateStringAttribute(goStackGrowthStatepointAttr, ""))
+	// A //go:nosplit function must not acquire that late morestack edge. Besides
+	// violating the runtime's nosplit call graph, it would expose a safepoint the
+	// frontend deliberately prohibited. Give target frame lowering the source
+	// policy directly instead of asking it to infer a pragma from GoObj metadata.
+	if f.NoSplit {
+		FCtxt.LF.AddFunctionAttr(GlobalCtxt.CreateStringAttribute(goNoSplitAttr, ""))
+	}
+	// Native Go gives //go:systemstack functions a distinct stack-growth
+	// prologue: it checks g.stackguard1 and calls runtime.morestackc. Carry the
+	// source pragma through AttrCFunc so target frame lowering cannot silently
+	// use the ordinary goroutine stack-growth protocol for runtime code.
+	if f.OwnAux.Fn.CFunc() {
+		FCtxt.LF.AddFunctionAttr(GlobalCtxt.CreateStringAttribute(goSystemStackAttr, ""))
+	}
 	FCtxt.LF.AddFunctionAttr(GlobalCtxt.CreateStringAttribute(llvmFramePointerAttr, llvmFramePointerNonLeaf))
 	if sig.HasClosureContext {
 		FCtxt.ClosureContext = FCtxt.LF.Param(sig.ClosureContextIndex)

src/cmd/internal/testdir/llvm_abi_test.go

@@ -22,14 +22,29 @@ import (
 type llvmABIDocument struct {
 	Members []struct {
 		GoObject *struct {
-			Symbols []llvmABISymbol `json:"symbols"`
+			Symbols    []llvmABISymbol `json:"symbols"`
+			References []llvmABISymbol `json:"references"`
 		} `json:"go_object"`
 	} `json:"members"`
 }
 
-type llvmABISymbol struct {
+type llvmABIReference struct {
+	PkgKind  string `json:"pkg_kind"`
+	SymIndex uint32 `json:"sym_index"`
 	Name     string `json:"name"`
-	ABI      uint16 `json:"abi"`
+}
+
+type llvmABISymbol struct {
+	Class       string   `json:"class"`
+	ClassIndex  uint32   `json:"class_index"`
+	Name        string   `json:"name"`
+	ABI         uint16   `json:"abi"`
+	Flags       uint64   `json:"flags"`
+	FlagNames   []string `json:"flag_names"`
+	Relocations []struct {
+		Type   string           `json:"type"`
+		Target llvmABIReference `json:"target"`
+	} `json:"relocations"`
 	Function *struct {
 		Info *struct {
 			Args   uint32 `json:"args"`
@@ -132,12 +147,14 @@ func runLLVMAArch64ABIDifferentialTest(t *testing.T, gorootTestDir string) {
 		[]byte("define goabiinternal"),
 		[]byte(`"go_results_tuple"`),
 		[]byte(`gc "goallc"`),
-		[]byte(`"go-stack-growth-statepoint"`),
 	} {
 		if !bytes.Contains(ir, needle) {
 			t.Fatalf("GoALLC IR does not contain %q", needle)
 		}
 	}
+	if bytes.Contains(ir, []byte(`"go-stack-growth-statepoint"`)) {
+		t.Fatal("GoALLC IR still contains the obsolete stack-growth attribute")
+	}
 
 	opt := llvmToolPath(t, "opt", "GOALLC_OPT")
 	runLLVMABICommand(t, ir, opt, "-passes=verify", "-disable-output")
@@ -248,7 +265,7 @@ func runLLVMAArch64ABIDifferentialTest(t *testing.T, gorootTestDir string) {
 			// homes in LocalsPointerMaps through locals-only alloca records.
 			goallcArgsMaps:  [][]int{{2, 4, 18}, {2}},
 			nativeStackMaps: []int32{-1, 0, -1},
-			goallcStackMaps: []int32{-1, 1, -1},
+			goallcStackMaps: []int32{-1, 1, -1, 1},
 			goallcQueryMaps: [][]int{{2, 4, 18}, {2}, {2}, {2}, {2}},
 		},
 		{
@@ -347,7 +364,8 @@ func runLLVMAArch64ABIDifferentialTest(t *testing.T, gorootTestDir string) {
 			nativeArgsMaps:  [][]int{{4}, nil},
 			goallcArgsMaps:  [][]int{{4}, nil, nil},
 			nativeStackMaps: []int32{-1, 0, 1, -1},
-			goallcStackMaps: []int32{-1, 1, 2, -1, 2},
+			goallcStackMaps: []int32{-1, 1, -1, 2},
+			goallcQueryMaps: [][]int{{4}, nil, nil, nil},
 		},
 	}
 	for _, tc := range cases {
@@ -955,6 +973,42 @@ func findLLVMABISymbol(t *testing.T, document llvmABIDocument, name string) llvm
 	return llvmABISymbol{}
 }
 
+func llvmABIRelocationTargetName(document llvmABIDocument, target llvmABIReference) string {
+	if target.Name != "" || target.PkgKind != "none" {
+		return target.Name
+	}
+	for _, member := range document.Members {
+		if member.GoObject == nil {
+			continue
+		}
+		var nonpackageDefinitions uint32
+		for _, symbol := range member.GoObject.Symbols {
+			if symbol.Class == "nonpackage" && symbol.ClassIndex >= nonpackageDefinitions {
+				nonpackageDefinitions = symbol.ClassIndex + 1
+			}
+		}
+		if target.SymIndex < nonpackageDefinitions {
+			continue
+		}
+		classIndex := target.SymIndex - nonpackageDefinitions
+		for _, reference := range member.GoObject.References {
+			if reference.Class == "nonpackage_reference" && reference.ClassIndex == classIndex {
+				return reference.Name
+			}
+		}
+	}
+	return ""
+}
+
+func llvmABIHasRelocationTo(document llvmABIDocument, symbol llvmABISymbol, name string) bool {
+	for _, relocation := range symbol.Relocations {
+		if llvmABIRelocationTargetName(document, relocation.Target) == name {
+			return true
+		}
+	}
+	return false
+}
+
 func checkLLVMABISymbol(t *testing.T, backend string, symbol llvmABISymbol, tc llvmABICase) {
 	t.Helper()
 	if symbol.ABI != 1 {

src/cmd/internal/testdir/llvm_test.go

@@ -15,7 +15,9 @@ import (
 	"os/exec"
 	"path"
 	"path/filepath"
+	"regexp"
 	"runtime"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -189,6 +191,7 @@ func runLLVMInfrastructureTests(t *testing.T, common testCommon) {
 		runLLVMCallerStateTest(t, common.gorootTestDir)
 	})
 	t.Run("getg-abi0-fail-closed", runLLVMGetGABI0FailClosedTest)
+	t.Run("nosplit", runLLVMNoSplitTest)
 	t.Run("writebarrier-helpers", runLLVMWriteBarrierHelperTest)
 	t.Run("compile-only-regressions", func(t *testing.T) {
 		for _, name := range []string{"cmp.go", "typeparam/issue47684c.go"} {
@@ -200,6 +203,91 @@ func runLLVMInfrastructureTests(t *testing.T, common testCommon) {
 	t.Run("writebarrier-ir", runLLVMWriteBarrierIRTests)
 }
 
+func runLLVMNoSplitTest(t *testing.T) {
+	t.Helper()
+	dir := t.TempDir()
+	source := filepath.Join(dir, "nosplit.go")
+	program := `package p
+
+func use(*[32]uintptr)
+
+//go:nosplit
+//go:noinline
+func NoSplit(pointer *int) *int {
+	var words [32]uintptr
+	use(&words)
+	return pointer
+}
+
+//go:noinline
+func Split(pointer *int) *int {
+	var words [32]uintptr
+	use(&words)
+	return pointer
+}
+`
+	if err := os.WriteFile(source, []byte(program), 0o666); err != nil {
+		t.Fatal(err)
+	}
+	archive := filepath.Join(dir, "nosplit.a")
+	runLLVMABICommand(t, nil, goTool, "tool", "compile",
+		"-p=p", "-enablellvm", "-llvmironly", "-o", archive, source)
+	ir, err := os.ReadFile(archive + ".ll")
+	if err != nil {
+		t.Fatal(err)
+	}
+	attributeLine := func(name string) []byte {
+		definition := regexp.MustCompile(`(?m)^define goabiinternal .*@` + regexp.QuoteMeta(name) + `\([^\n]*\) #([0-9]+)`).FindSubmatch(ir)
+		if definition == nil {
+			t.Fatalf("LLVM IR has no attributed definition for %s\n%s", name, ir)
+		}
+		pattern := regexp.MustCompile(`(?m)^attributes #` + string(definition[1]) + ` = \{.*$`)
+		line := pattern.Find(ir)
+		if line == nil {
+			t.Fatalf("LLVM IR has no attribute group for %s\n%s", name, ir)
+		}
+		return line
+	}
+	noSplitAttrs := attributeLine("p.NoSplit")
+	if !bytes.Contains(noSplitAttrs, []byte(`"go-nosplit"`)) ||
+		!bytes.Contains(noSplitAttrs, []byte(`noinline`)) {
+		t.Fatalf("LLVM nosplit attributes do not select the nosplit prologue policy: %s", noSplitAttrs)
+	}
+	splitAttrs := attributeLine("p.Split")
+	if bytes.Contains(splitAttrs, []byte(`"go-nosplit"`)) {
+		t.Fatalf("LLVM split attributes do not select the stack-growth prologue policy: %s", splitAttrs)
+	}
+	if bytes.Contains(ir, []byte(`"go-stack-growth-statepoint"`)) {
+		t.Fatal("LLVM IR still contains the obsolete stack-growth attribute")
+	}
+
+	llc := llvmToolPath(t, "llc", "GOALLC_LLC")
+	plugin := llvmABIPassPlugin(t, llc)
+	object := filepath.Join(dir, "nosplit.o")
+	runLLVMABICommand(t, nil, llc, "-load-pass-plugin="+plugin,
+		"-verify-machineinstrs", "-filetype=obj", "-o", object, archive+".ll")
+	document := readLLVMABIObject(t, object)
+	noSplit := findLLVMABISymbol(t, document, "p.NoSplit")
+	if !slices.Contains(noSplit.FlagNames, "nosplit") {
+		t.Fatalf("p.NoSplit GoObj flags %v do not contain nosplit", noSplit.FlagNames)
+	}
+	if llvmABIHasRelocationTo(document, noSplit, "runtime.morestack_noctxt") {
+		t.Fatal("p.NoSplit unexpectedly calls runtime.morestack_noctxt")
+	}
+	noSplitArgs := llvmABIArgsPointerBitmaps(t, noSplit)
+	if len(noSplitArgs) == 0 || !slices.Equal(noSplitArgs[0], []int{0}) {
+		t.Fatalf("p.NoSplit entry ArgsPointerMaps = %v, want pointer bit 0", noSplitArgs)
+	}
+	split := findLLVMABISymbol(t, document, "p.Split")
+	if !llvmABIHasRelocationTo(document, split, "runtime.morestack_noctxt") {
+		t.Fatal("p.Split has no runtime.morestack_noctxt relocation")
+	}
+	splitArgs := llvmABIArgsPointerBitmaps(t, split)
+	if len(splitArgs) == 0 || !slices.Equal(splitArgs[0], []int{0}) {
+		t.Fatalf("p.Split entry ArgsPointerMaps = %v, want pointer bit 0", splitArgs)
+	}
+}
+
 func runLLVMGetGABI0FailClosedTest(t *testing.T) {
 	t.Helper()
 	dir := t.TempDir()

src/cmd/llvmplugin/CMakeLists.txt

@@ -21,9 +21,9 @@ add_definitions(${LLVM_DEFINITIONS})
 include_directories(SYSTEM ${LLVM_INCLUDE_DIRS})
 
 add_llvm_pass_plugin(GoALLCStatepoints
+  GoALLCStackMapPrinter.cpp
   GoALLCInlineAnchors.cpp
   GoALLCPreCodeGen.cpp
-  GoALLCStackMapPrinter.cpp
   GoALLCStatepoints.cpp
   GoALLCStatepointPlugin.cpp
 )
@@ -252,7 +252,7 @@ if(BUILD_TESTING)
   )
   set_tests_properties(GoALLCStatepoints.FrontendMarkersPreserved PROPERTIES
     PASS_REGULAR_EXPRESSION
-      "go-stack-growth-statepoint"
+      "gc \"goallc\""
   )
 
   foreach(GOALLC_DEBUG_TARGET IN ITEMS X86 AArch64)
@@ -505,6 +505,17 @@ if(BUILD_TESTING)
         DEPENDS GoALLCStatepoints.DebugInline${GOALLC_DEBUG_TARGET}GoObj
       )
     endforeach()
+    goallc_add_filecheck_test(
+      GoALLCStatepoints.GoObjStackMaps
+      "${CMAKE_CURRENT_SOURCE_DIR}/testdata/statepoint.ll"
+      OBJVIEW-TEXT
+      "${GOALLC_OBJVIEW_EXECUTABLE}" -format=text
+      "${CMAKE_CURRENT_BINARY_DIR}/statepoint.goobj"
+    )
+    set_tests_properties(GoALLCStatepoints.GoObjStackMaps PROPERTIES
+      DEPENDS GoALLCStatepoints.GoObj
+    )
+
     goallc_add_filecheck_test(
       GoALLCStatepoints.DeferEdgeObjView
       "${CMAKE_CURRENT_SOURCE_DIR}/testdata/defer-edge.ll"