Start inferring return types for static functions

Start inferring return types for static functions

Types propagated to the function exit are recorded in the code generator
and optimisticly used at call sites. If this optimistic assumption fails
the callers have to be recompiled.

R=kasperl, ngeoffray, floitsch

Committed: https://code.google.com/p/dart/source/detail?r=10876

[ngeoffray, 2012-08-17 10:02:51]

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/js_backend/backend.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:405: * Retreive the return
type of the function [calee]. The type is optimistic
why not callee?

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:406: * in the sense that is
is based on the compilation og [calee]. If [calee] is
og -> of

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:408: * reason [calller] is
registered for recompilation if this happens. If the
calller -> caller

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:413:
returnInfo.putIfAbsent(calee, () => new ReturnInfo.unknownType());
Why do you need to put a return info? Could you just return null if there is no
return info?

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/codegen.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/codegen.dart:33: if (block.last is HReturn) {
How about a function with multiple return?

[Søren Gjesse, 2012-08-17 10:08:53]

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/js_backend/backend.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:405: * Retreive the return
type of the function [calee]. The type is optimistic
On 2012/08/17 10:02:51, ngeoffray wrote:
> why not callee?

Because I cannot spell - fixed.

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:406: * in the sense that is
is based on the compilation og [calee]. If [calee] is
On 2012/08/17 10:02:51, ngeoffray wrote:
> og -> of

Done.

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:408: * reason [calller] is
registered for recompilation if this happens. If the
On 2012/08/17 10:02:51, ngeoffray wrote:
> calller -> caller

Done.

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:413:
returnInfo.putIfAbsent(calee, () => new ReturnInfo.unknownType());
On 2012/08/17 10:02:51, ngeoffray wrote:
> Why do you need to put a return info? Could you just return null if there is
no
> return info?

The ReturnInfo with returnType null indicates that there are callers but the
callee has not been compiled yet. When the callee is compiled the callers will
be re-compiled - unless the return type of the callee turns out to be
HType.UNKNOWN.

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/codegen.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/codegen.dart:33: if (block.last is HReturn) {
On 2012/08/17 10:02:51, ngeoffray wrote:
> How about a function with multiple return?

This should be handled by the

graph.exit.predecessors.forEach((block) {

above.

[kasperl, 2012-08-17 10:11:07]

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/js_backend/backend.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:405: * Retreive the return
type of the function [calee]. The type is optimistic
i before e except after c (Retrieve).

[ngeoffray, 2012-08-17 10:13:29]

LGTM

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/codegen.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/codegen.dart:33: if (block.last is HReturn) {
On 2012/08/17 10:08:54, Søren Gjesse wrote:
> On 2012/08/17 10:02:51, ngeoffray wrote:
> > How about a function with multiple return?
> 
> This should be handled by the
> 
> graph.exit.predecessors.forEach((block) {
> 
> above.

Hmm, a HReturn block has the HExit block as a successor? Is that always true and
checked?

To make it simpler in the SSA, maybe we should have one HReturn and all return
values flow into a phi in the exit block, which will contain the HReturn.

[Søren Gjesse, 2012-08-17 10:21:04]

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/js_backend/backend.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/js_backend/backend.dart:405: * Retreive the return
type of the function [calee]. The type is optimistic
On 2012/08/17 10:11:07, kasperl wrote:
> i before e except after c (Retrieve).

Done.

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/codegen.dart (right):

https://chromiumcodereview.appspot.com/10823389/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/codegen.dart:33: if (block.last is HReturn) {
On 2012/08/17 10:13:29, ngeoffray wrote:
> On 2012/08/17 10:08:54, Søren Gjesse wrote:
> > On 2012/08/17 10:02:51, ngeoffray wrote:
> > > How about a function with multiple return?
> > 
> > This should be handled by the
> > 
> > graph.exit.predecessors.forEach((block) {
> > 
> > above.
> 
> Hmm, a HReturn block has the HExit block as a successor? Is that always true
and
> checked?
> 
> To make it simpler in the SSA, maybe we should have one HReturn and all return
> values flow into a phi in the exit block, which will contain the HReturn.

I checked the (3) places where HReturn nodes are created, which is how I got to
this in the first place. For functions which don't return a value a HGoto is
normally taking control flow to the HExit node.