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Convert some switch statements to if-then-else

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This commit is contained in:
Kevin Glynn 2011-01-20 12:33:29 +01:00
parent 7d6a95b347
commit 4c882a08e2
2 changed files with 144 additions and 7 deletions
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149
CSharpTranslator/antlr3/src/cs2j/CSharp/NetMaker.g
View File

@ -151,6 +151,76 @@ scope SymTab {
return (CommonTree)adaptor.DupTree(t);
}
protected static readonly string[] ScruTypeStrs = new string[] { "System.Int32",
"System.Int64",
"System.Char",
"System.Enum",
};
protected bool typeIsInvalidForScrutinee(TypeRepTemplate sType) {
bool ret = true;
foreach (string t in ScruTypeStrs)
{
if (sType.IsA(AppEnv.Search(t), AppEnv))
{
ret = false;
break;
}
}
return ret;
}
// counter to ensure that the catch vars we introduce are unique
protected int dummyScrutVarCtr = 0;
protected CommonTree convertSectionsToITE(List sections) {
CommonTree ret = null;
if (sections != null && sections.Count > 0) {
ret = dupTree((CommonTree)sections[sections.Count - 1]);
for(int i = sections.Count - 2; i >= 0; i--) {
CommonTree section = dupTree((CommonTree)sections[i]);
// section is either ^(IF ...) or "else ^(IF ....)" we need to insert ret into the IF
if (section.IsNil) {
section.Children[section.Children.Count-1].AddChild(ret);
}
else {
section.AddChild(ret);
}
ret = section;
}
}
return ret;
}
// In switch sections we want to remove final break statements if we have converted to if-then-else
protected CommonTree stripFinalBreak(CommonTree stats) {
CommonTree ret = stats;
if (stats.IsNil) {
// A list of statements
// look for an ending of "break [;]"
int len = stats.Children.Count;
int breakPos = len - 1;
if ( len > 1 && stats.Children[len-1].Type == SEMI ) {
breakPos = len -2;
}
if (stats.Children[breakPos].Type != BREAK) {
// not found
breakPos = -1;
}
if (breakPos > 0) {
// delete from break to end
for (int i = len-1; i >= breakPos; i--) {
stats.DeleteChild(i);
}
}
}
return ret;
}
}
compilation_unit
@ -1154,8 +1224,31 @@ embedded_statement:
switch_statement
scope {
bool isEnum;
bool convertToIfThenElse;
string scrutVar;
bool isFirstCase;
}
@init {
$switch_statement::isEnum = false;
$switch_statement::convertToIfThenElse = false;
$switch_statement::scrutVar = "WHOOPS";
$switch_statement::isFirstCase = true;
}:
^('switch' expression { $switch_statement::isEnum = $expression.dotNetType != null && $expression.dotNetType.IsA(AppEnv.Search("System.Enum"), AppEnv); } switch_section*)
^(s='switch' se=expression sv=magicScrutineeVar[$s.token]
{
if ($expression.dotNetType != null) {
$switch_statement::isEnum = $expression.dotNetType.IsA(AppEnv.Search("System.Enum"), AppEnv);
$switch_statement::convertToIfThenElse = typeIsInvalidForScrutinee($expression.dotNetType);
$switch_statement::scrutVar = $sv.thetext;
}
}
ss+=switch_section*)
-> { $switch_statement::convertToIfThenElse }?
// TODO: down the line, check if scrutinee is already a var and reuse that.
// TYPE{ String } ret ;
^(TYPE[$s.token, "TYPE"] IDENTIFIER[$s.token,$expression.dotNetType.Java]) $sv ASSIGN[$s.token, "="] { dupTree($se.tree) } SEMI[$s.token, ";"]
{ convertSectionsToITE($ss) }
-> ^($s expression $ss*)
;
fixed_statement:
'fixed' '(' pointer_type fixed_pointer_declarators ')' embedded_statement ;
@ -1198,12 +1291,49 @@ statement_expression:
;
else_statement:
'else' embedded_statement ;
switch_section:
^(SWITCH_SECTION switch_label+ statement_list) ;
switch_label:
^(c='case' ce=constant_expression ) -> { $switch_statement::isEnum && $constant_expression.rmId != null}? ^($c IDENTIFIER[$c.token, $constant_expression.rmId])
-> ^($c $ce)
| 'default';
switch_section
@init {
bool defaultSection = false;
}
@after{
$switch_statement::isFirstCase = false;
}:
^(s=SWITCH_SECTION ({$switch_statement::convertToIfThenElse}? ite_switch_labels | switch_labels) sl=statement_list)
{
}
-> {$switch_statement::convertToIfThenElse && $switch_statement::isFirstCase && $ite_switch_labels.isDefault}? { stripFinalBreak($sl.tree) }
-> {$switch_statement::convertToIfThenElse && $ite_switch_labels.isDefault}? ELSE[$s.token, "else"] OPEN_BRACE[$s.token, "{"] { stripFinalBreak($sl.tree) } CLOSE_BRACE[$s.token, "}"]
-> {$switch_statement::convertToIfThenElse && $switch_statement::isFirstCase}? ^(IF[$s.token, "if"] ite_switch_labels SEP OPEN_BRACE[$s.token, "{"] { stripFinalBreak($sl.tree) } CLOSE_BRACE[$s.token, "}"])
-> {$switch_statement::convertToIfThenElse}? ELSE[$s.token, "else"] ^(IF[$s.token, "if"] ite_switch_labels SEP OPEN_BRACE[$s.token, "{"] { stripFinalBreak($sl.tree) } CLOSE_BRACE[$s.token, "}"])
-> ^($s switch_labels statement_list)
;
ite_switch_labels returns [bool isDefault]
@init {
$isDefault = false;
}:
(l1=switch_label { if($l1.isDefault) $isDefault = true; } -> $l1)
(ln=switch_label { if($ln.isDefault) $isDefault = true; } -> ^(LOG_OR[$ln.tree.Token, "||"] { dupTree($ite_switch_labels.tree) } { dupTree($ln.tree) }) )*
;
switch_labels returns [bool isDefault]
@init {
$isDefault = false;
}:
switch_label+
;
switch_label returns [bool isDefault]
@init {
$isDefault = false;
}:
^(c='case' ce=constant_expression )
-> { $switch_statement::convertToIfThenElse }?
// scrutVar.equals(ce)
^(APPLY[$c.token, "APPLY"] ^(DOT[$c.token, "."] IDENTIFIER[$c.token, $switch_statement::scrutVar] IDENTIFIER[$c.token, "equals"]) ^(ARGS[$c.token, "ARGS"] $ce))
-> { $switch_statement::isEnum && $constant_expression.rmId != null}? ^($c IDENTIFIER[$c.token, $constant_expression.rmId])
-> ^($c $ce)
| 'default' { $isDefault = true; };
iteration_statement
scope SymTab;
@init {
@ -1320,3 +1450,8 @@ literal returns [TypeRepTemplate dotNetType]
| NULL { ns = "System.Object"; }
;
magicScrutineeVar [IToken tok] returns [String thetext]
@init {
$thetext = "__dummyScrutVar" + dummyScrutVarCtr++;
}:
-> IDENTIFIER[tok,$thetext];

2
CSharpTranslator/antlr3/src/cs2j/CSharp/cs.g
View File

@ -59,6 +59,8 @@ tokens {
CATCH = 'catch';
FINALLY = 'finally';
THROW = 'throw';
ELSE = 'else';
BREAK = 'break';
OPEN_BRACKET='[';
CLOSE_BRACKET=']';