Implement simple switch statements as nested if/else.

Implement simple switch statements as nested if/else.

Simple switch statements that do not have continue to labeled cases
are compiled into a chain if/else comparisons.

R=asgerf@google.com

Committed: https://github.com/dart-lang/sdk/commit/bf595224d58bd175945e9a91df86553936833b7f

[Kevin Millikin (Google), 2015-06-19 11:27:06]

kmillikin@google.com changed reviewers:
+ asgerf@google.com

[asgerf, 2015-06-19 12:47:34]

LGTM

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
File pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart (right):

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:1658: for (SwitchCaseInfo
caseInfo in cases) {
Anonymize buildRight? I don't understand the name anyway.

buildConditionFrom(int index) => (IrBuilder builder) {
  ...
}

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:1697: elseContinuation)));
The rule that the first continuation of LetCont becomes the "current" node to
continue on is quite subtle. I was confused here for a while because I couldn't
see any obvious indicator that 'else' would be continued in the next iteration.

Not specific to this CL at all, but I'm wondering if we can make that nicer
somehow.

[Kevin Millikin (Google), 2015-06-19 12:59:52]

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
File pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart (right):

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:1658: for (SwitchCaseInfo
caseInfo in cases) {
On 2015/06/19 12:47:34, asgerf wrote:
> Anonymize buildRight? I don't understand the name anyway.
> 
> buildConditionFrom(int index) => (IrBuilder builder) {
>   ...
> }

Yeah, that's how I wrote it in my head, but I wanted to put a return type
annotation for some reason.  It's 2015 and we are still repeating C's
"declaration mimics use" mistake.

I'm happy to change it as you suggest!

https://codereview.chromium.org/1191193005/diff/20001/pkg/compiler/lib/src/cp...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:1697: elseContinuation)));
On 2015/06/19 12:47:34, asgerf wrote:
> The rule that the first continuation of LetCont becomes the "current" node to
> continue on is quite subtle. I was confused here for a while because I
couldn't
> see any obvious indicator that 'else' would be continued in the next
iteration.
> 
> Not specific to this CL at all, but I'm wondering if we can make that nicer
> somehow.

There is a comment everywhere else, I'll duplicate it here.

Only one should have a null body, so we could use that as an indicator and allow
them to be in whatever order is natural but that's subtle too.

[Kevin Millikin (Google), 2015-06-22 09:29:47]

Committed patchset #4 (id:60001) manually as
bf595224d58bd175945e9a91df86553936833b7f (presubmit successful).