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Use ES 2015 syntax to generate more compact code for blocking functions. #1137

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Merged
merged 3 commits into from
Aug 16, 2022
Merged

Use ES 2015 syntax to generate more compact code for blocking functions. #1137

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2dc0286
Use ES2015 syntax for more compact context save/restore.
nevkontakte Aug 1, 2022
cea2ae1
Further compactify blocking function context save/restore code.
nevkontakte Aug 7, 2022
3067214
Optimize goroutine switching performance.
nevkontakte Aug 13, 2022
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32 changes: 21 additions & 11 deletions compiler/package.go
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Original file line number Diff line number Diff line change
Expand Up @@ -805,7 +805,7 @@ func translateFunction(typ *ast.FuncType, recv *ast.Ident, body *ast.BlockStmt,

if len(c.Flattened) != 0 {
c.localVars = append(c.localVars, "$s")
prefix = prefix + " $s = 0;"
prefix = prefix + " $s = $s || 0;"
}

if c.HasDefer {
Expand All @@ -816,19 +816,29 @@ func translateFunction(typ *ast.FuncType, recv *ast.Ident, body *ast.BlockStmt,
}
}

localVarDefs := "" // Function-local var declaration at the top.

if len(c.Blocking) != 0 {
c.localVars = append(c.localVars, "$r")
if funcRef == "" {
funcRef = "$b"
functionName = " $b"
}
var stores, loads string
for _, v := range c.localVars {
loads += fmt.Sprintf("%s = $f.%s; ", v, v)
stores += fmt.Sprintf("$f.%s = %s; ", v, v)
}
prefix = prefix + " var $f, $c = false; if (this !== undefined && this.$blk !== undefined) { $f = this; $c = true; " + loads + "}"
suffix = " if ($f === undefined) { $f = { $blk: " + funcRef + " }; } " + stores + "return $f;" + suffix

localVars := append([]string{}, c.localVars...)
// There are several special variables involved in handling blocking functions:
// $r is sometimes used as a temporary variable to store blocking call result.
// $c indicates that a function is being resumed after a blocking call when set to true.
// $f is an object used to save and restore function context for blocking calls.
localVars = append(localVars, "$r")
// If a blocking function is being resumed, initialize local variables from the saved context.
localVarDefs = fmt.Sprintf("var {%s, $c} = $restore(this, {%s});\n", strings.Join(localVars, ", "), strings.Join(params, ", "))
// If the function gets blocked, save local variables for future.
saveContext := fmt.Sprintf("var $f = {$blk: "+funcRef+", $c: true, $r, %s};", strings.Join(c.localVars, ", "))

suffix = " " + saveContext + "return $f;" + suffix
} else if len(c.localVars) > 0 {
// Non-blocking functions simply declare local variables with no need for restore support.
localVarDefs = fmt.Sprintf("var %s;\n", strings.Join(c.localVars, ", "))
}

if c.HasDefer {
Expand Down Expand Up @@ -865,8 +875,8 @@ func translateFunction(typ *ast.FuncType, recv *ast.Ident, body *ast.BlockStmt,
if suffix != "" {
bodyOutput = bodyOutput + strings.Repeat("\t", c.pkgCtx.indentation+1) + "/* */" + suffix + "\n"
}
if len(c.localVars) != 0 {
bodyOutput = fmt.Sprintf("%svar %s;\n", strings.Repeat("\t", c.pkgCtx.indentation+1), strings.Join(c.localVars, ", ")) + bodyOutput
if localVarDefs != "" {
bodyOutput = strings.Repeat("\t", c.pkgCtx.indentation+1) + localVarDefs + bodyOutput
}

c.pkgCtx.escapingVars = prevEV
Expand Down
7 changes: 7 additions & 0 deletions compiler/prelude/goroutines.go
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Original file line number Diff line number Diff line change
Expand Up @@ -223,6 +223,13 @@ var $block = function() {
$curGoroutine.asleep = true;
};

var $restore = function(context, params) {
if (context !== undefined && context.$blk !== undefined) {
return context;
}
return params;
}

var $send = function(chan, value) {
if (chan.$closed) {
$throwRuntimeError("send on closed channel");
Expand Down
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