func ProfileGuided(fn *ir.Func, p *pgo.Profile)
ProfileGuided performs call devirtualization of indirect calls based on profile information.
Specifically, it performs conditional devirtualization of interface calls or function value calls for the hottest callee.
That is, for interface calls it performs a transformation like:
type Iface interface {
Foo()
}
type Concrete struct{}
func (Concrete) Foo() {}
func foo(i Iface) {
i.Foo()
}
to:
func foo(i Iface) {
if c, ok := i.(Concrete); ok {
c.Foo()
} else {
i.Foo()
}
}
For function value calls it performs a transformation like:
func Concrete() {}
func foo(fn func()) {
fn()
}
to:
func foo(fn func()) {
if internal/abi.FuncPCABIInternal(fn) == internal/abi.FuncPCABIInternal(Concrete) {
Concrete()
} else {
fn()
}
}
The primary benefit of this transformation is enabling inlining of the direct call.
func StaticCall(call *ir.CallExpr)
StaticCall devirtualizes the given call if possible when the concrete callee is available statically.
CallStat summarizes a single call site.
This is used only for debug logging.
type CallStat struct {
Pkg string // base.Ctxt.Pkgpath
Pos string // file:line:col of call.
Caller string // Linker symbol name of calling function.
// Direct or indirect call.
Direct bool
// For indirect calls, interface call or other indirect function call.
Interface bool
// Total edge weight from this call site.
Weight int64
// Hottest callee from this call site, regardless of type
// compatibility.
Hottest string
HottestWeight int64
// Devirtualized callee if != "".
//
// Note that this may be different than Hottest because we apply
// type-check restrictions, which helps distinguish multiple calls on
// the same line.
Devirtualized string
DevirtualizedWeight int64
}