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feat: improve pprof experience by adding wrappers to interpreted functions #1712

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28 changes: 28 additions & 0 deletions interp/cfg.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1612,6 +1612,34 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
n.types, n.scope = sc.types, sc
sc = sc.pop()
funcName := n.child[1].ident

// Pre-calculate pprof label and assign wrapper level for this function
pkgName := ""
if sc.pkgID != "" {
pkgName = sc.pkgID
}
receiverType := ""
if isMethod(n) && len(n.child) > 0 && len(n.child[0].child) > 0 {
// Extract receiver type name from AST
recvNode := n.child[0].child[0].lastChild()
if recvNode.ident != "" {
// Simple identifier (e.g., Handler)
receiverType = recvNode.ident
} else if len(recvNode.child) > 0 && recvNode.child[0].ident != "" {
// Pointer receiver (e.g., *Handler)
receiverType = "*" + recvNode.child[0].ident
}
}
// Build label: "pkg:receiver:func" or "pkg::func" for top-level functions
if receiverType != "" {
n.pprofLabel = pkgName + ":" + receiverType + ":" + funcName
} else {
n.pprofLabel = pkgName + "::" + funcName
}

// Assign wrapper level and cache wrapper function for performance
n.wrapperLevel = interp.assignWrapperLevel(n.pprofLabel, n)

if sym := sc.sym[funcName]; !isMethod(n) && sym != nil && !isGeneric(sym.typ) {
sym.index = -1 // to force value to n.val
sym.typ = n.typ
Expand Down
37 changes: 37 additions & 0 deletions interp/gen_wrappers.go
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@@ -0,0 +1,37 @@
//go:build ignore

package main

import (
"fmt"
)

// Generator for wrapper functions.
// Run with: go run gen_wrappers.go > wrappers_generated.go
func main() {
fmt.Println("package interp")
fmt.Println()
fmt.Println("// Code generated by gen_wrappers.go; DO NOT EDIT.")
fmt.Println()

// Generate 500 wrapper functions
for i := 0; i < 500; i++ {
fmt.Printf("//go:noinline\n")
fmt.Printf("func wrapperLevel%d(start *node, fr *frame, def, n *node) {\n", i)
fmt.Printf("\trunCfg(start, fr, def, n)\n")
fmt.Printf("}\n\n")
}

// Generate the dispatcher function
fmt.Println("// getWrapperByLevel returns the appropriate wrapper function based on level.")
fmt.Println("func getWrapperByLevel(level int) func(*node, *frame, *node, *node) {")
fmt.Println("\tswitch level {")
for i := 0; i < 500; i++ {
fmt.Printf("\tcase %d:\n", i)
fmt.Printf("\t\treturn wrapperLevel%d\n", i)
}
fmt.Println("\tdefault:")
fmt.Println("\t\treturn wrapperLevel0")
fmt.Println("\t}")
fmt.Println("}")
}
128 changes: 83 additions & 45 deletions interp/interp.go
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Expand Up @@ -25,34 +25,37 @@ import (

// Interpreter node structure for AST and CFG.
type node struct {
debug *nodeDebugData // debug info
child []*node // child subtrees (AST)
anc *node // ancestor (AST)
param []*itype // generic parameter nodes (AST)
start *node // entry point in subtree (CFG)
tnext *node // true branch successor (CFG)
fnext *node // false branch successor (CFG)
interp *Interpreter // interpreter context
index int64 // node index (dot display)
findex int // index of value in frame or frame size (func def, type def)
level int // number of frame indirections to access value
nleft int // number of children in left part (assign) or indicates preceding type (compositeLit)
nright int // number of children in right part (assign)
kind nkind // kind of node
pos token.Pos // position in source code, relative to fset
sym *symbol // associated symbol
typ *itype // type of value in frame, or nil
recv *receiver // method receiver node for call, or nil
types []reflect.Type // frame types, used by function literals only
scope *scope // frame scope
action action // action
exec bltn // generated function to execute
gen bltnGenerator // generator function to produce above bltn
val interface{} // static generic value (CFG execution)
rval reflect.Value // reflection value to let runtime access interpreter (CFG)
ident string // set if node is a var or func
redeclared bool // set if node is a redeclared variable (CFG)
meta interface{} // meta stores meta information between gta runs, like errors
debug *nodeDebugData // debug info
child []*node // child subtrees (AST)
anc *node // ancestor (AST)
param []*itype // generic parameter nodes (AST)
start *node // entry point in subtree (CFG)
tnext *node // true branch successor (CFG)
fnext *node // false branch successor (CFG)
interp *Interpreter // interpreter context
index int64 // node index (dot display)
findex int // index of value in frame or frame size (func def, type def)
level int // number of frame indirections to access value
nleft int // number of children in left part (assign) or indicates preceding type (compositeLit)
nright int // number of children in right part (assign)
kind nkind // kind of node
pos token.Pos // position in source code, relative to fset
sym *symbol // associated symbol
typ *itype // type of value in frame, or nil
recv *receiver // method receiver node for call, or nil
types []reflect.Type // frame types, used by function literals only
scope *scope // frame scope
action action // action
exec bltn // generated function to execute
gen bltnGenerator // generator function to produce above bltn
val interface{} // static generic value (CFG execution)
rval reflect.Value // reflection value to let runtime access interpreter (CFG)
ident string // set if node is a var or func
redeclared bool // set if node is a redeclared variable (CFG)
meta interface{} // meta stores meta information between gta runs, like errors
pprofLabel string // pre-calculated pprof label for this function (e.g., "pkg:receiver:func")
wrapperLevel int // assigned wrapper level for this function (0-499)
wrapperFunc func(*node, *frame, *node, *node) // pre-assigned wrapper function (cached for performance)
}

func (n *node) shouldBreak() bool {
Expand Down Expand Up @@ -208,11 +211,15 @@ type Interpreter struct {
frame *frame // program data storage during execution
universe *scope // interpreter global level scope
scopes map[string]*scope // package level scopes, indexed by import path
srcPkg imports // source packages used in interpreter, indexed by path
pkgNames map[string]string // package names, indexed by import path
done chan struct{} // for cancellation of channel operations
roots []*node
generic map[string]*node

// Wrapper level assignment for profiling
nextWrapperLevel int // next wrapper level to assign (0-499, wraps around)
levelToLabel map[int][]string // map from wrapper level to function labels (for GetWrapperMappings)
srcPkg imports // source packages used in interpreter, indexed by path
pkgNames map[string]string // package names, indexed by import path
done chan struct{} // for cancellation of channel operations
roots []*node
generic map[string]*node

hooks *hooks // symbol hooks

Expand Down Expand Up @@ -322,18 +329,19 @@ type Options struct {
// New returns a new interpreter.
func New(options Options) *Interpreter {
i := Interpreter{
opt: opt{context: build.Default, filesystem: &realFS{}, env: map[string]string{}},
frame: newFrame(nil, 0, 0),
fset: token.NewFileSet(),
universe: initUniverse(),
scopes: map[string]*scope{},
binPkg: Exports{"": map[string]reflect.Value{"_error": reflect.ValueOf((*_error)(nil))}},
mapTypes: map[reflect.Value][]reflect.Type{},
srcPkg: imports{},
pkgNames: map[string]string{},
rdir: map[string]bool{},
hooks: &hooks{},
generic: map[string]*node{},
opt: opt{context: build.Default, filesystem: &realFS{}, env: map[string]string{}},
frame: newFrame(nil, 0, 0),
fset: token.NewFileSet(),
universe: initUniverse(),
scopes: map[string]*scope{},
binPkg: Exports{"": map[string]reflect.Value{"_error": reflect.ValueOf((*_error)(nil))}},
mapTypes: map[reflect.Value][]reflect.Type{},
levelToLabel: map[int][]string{},
srcPkg: imports{},
pkgNames: map[string]string{},
rdir: map[string]bool{},
hooks: &hooks{},
generic: map[string]*node{},
}

if i.opt.stdin = options.Stdin; i.opt.stdin == nil {
Expand Down Expand Up @@ -760,3 +768,33 @@ func getPrompt(in io.Reader, out io.Writer) func(reflect.Value) {
}
return func(reflect.Value) {}
}

// assignWrapperLevel assigns a wrapper level for the given function.
// Functions are assigned incrementally (0-499) with wrap-around after 500 functions.
// Sets the wrapper function reference in the node for optimal performance (no runtime lookup).
func (interp *Interpreter) assignWrapperLevel(label string, n *node) int {
// Assign next available level
level := interp.nextWrapperLevel
interp.nextWrapperLevel = (interp.nextWrapperLevel + 1) % 500

// Store mapping for GetWrapperMappings() API
interp.levelToLabel[level] = append(interp.levelToLabel[level], label)

// Cache wrapper function in node for zero-lookup performance
n.wrapperFunc = getWrapperByLevel(level)

return level
}

// GetWrapperMappings returns the mapping of wrapper levels to function labels.
// This allows correlation of pprof stack traces (showing wrapperLevelN) to actual function names.
func (interp *Interpreter) GetWrapperMappings() map[int][]string {
interp.mutex.RLock()
defer interp.mutex.RUnlock()

result := make(map[int][]string, len(interp.levelToLabel))
for level, labels := range interp.levelToLabel {
result[level] = append([]string(nil), labels...)
}
return result
}
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