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go/ssa: remove optimization of 'rundefers'.

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The SSA builder shouldn't be in the business of
interprocedural optimization, especially in the presence of
concurrency.

This causes the instruction count to increase by 0.03%.

LGTM=gri
R=gri, pcc
CC=golang-codereviews
https://golang.org/cl/105020045
This commit is contained in:
Alan Donovan 2014-06-11 16:33:25 -04:00
parent cd36f52558
commit 30166088e4
2 changed files with 1 additions and 34 deletions
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19
go/ssa/builder.go
View File

@ -1918,24 +1918,7 @@ start:
// locals (which may be mutated by the deferred call)
// and return them.
if fn.namedResults != nil {
// Optimization: if we can prove the deferred call
// won't cause recovery from panic, we can avoid a
// Recover block.
// We scan the callee for calls to recover() iff:
// - it's a static call
// - to a function in the same package
// (other packages' SSA building happens concurrently)
// - whose SSA building has started (Blocks != nil)
// - and finished (i.e. not this function)
// NB, this is always true for: defer func() { ... } ()
//
// TODO(adonovan): optimize interpackage cases, e.g.
// (sync.Mutex).Unlock(), (io.Closer).Close
if callee, ok := v.Call.Value.(*Function); ok && callee.Pkg == fn.Pkg && callee != fn && callee.Blocks != nil && !callsRecover(callee) {
// Deferred call cannot cause recovery from panic.
} else {
createRecoverBlock(fn)
}
createRecoverBlock(fn)
}
case *ast.ReturnStmt:

16
go/ssa/util.go
View File

@ -103,22 +103,6 @@ func logStack(format string, args ...interface{}) func() {
}
}
// callsRecover reports whether f contains a direct call to recover().
func callsRecover(f *Function) bool {
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if call, ok := instr.(*Call); ok {
if blt, ok := call.Call.Value.(*Builtin); ok {
if blt.Name() == "recover" {
return true
}
}
}
}
}
return false
}
// newVar creates a 'var' for use in a types.Tuple.
func newVar(name string, typ types.Type) *types.Var {
return types.NewParam(token.NoPos, nil, name, typ)