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separate ASTVisitor.visit for ExpressionNode #490

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merged 1 commit into from
Mar 24, 2023
Merged

separate ASTVisitor.visit for ExpressionNode #490

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33 changes: 29 additions & 4 deletions src/dparse/ast.d
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Original file line number Diff line number Diff line change
Expand Up @@ -92,11 +92,32 @@ enum DeclarationListStyle : ubyte
*/
abstract class ASTVisitor
{

/** */
deprecated("Don't use or override visit(ExpressionNode). For usage: dynamicDispatch(ExpressionNode) is equivalent; "
~ "for overriding: you should probably override more specific cases. If you need to override to inject some "
~ "before/after code for all cases, make sure to call `super.dynamicDispatch(n)` instead of `n.accept(this)`!")
void visit(const ExpressionNode n)
{
switch (typeMap[typeid(n)])
dynamicDispatch(n);
}

/**
* Looks at the runtime type of `n`, then calls the appropriate `visit`
* method at runtime.
*
* Rule of thumb: when the type is an abstract class, use `dynamicDispatch`,
* otherwise use `visit`.
*
* For templated calls:
* ---
* static if (__traits(isAbstractClass, typeof(node)))
* visitor.dynamicDispatch(node);
* else
* visitor.visit(node);
* ---
*/
void dynamicDispatch(const ExpressionNode n)
{
switch (typeMap.get(typeid(n), 0))
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The following casts are not good as they could. There should be a bit cast based on the case:

case 1: visit(*cast(AddExpression*) &n); break;
/*etc*/
case 48: visit(*cast(XorExpression*) &n); break;

So far there are still dynamic casts, i.e calls to runtime _d_obj_cast, although those calls always succeed.

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I don't think using bitcasts for class inheritance is safe, since the cast manipulates the pointer value, e.g.

Casting a class object to an interface consists of adding the offset of the interface's corresponding vptr to the address of the base of the object. Casting an interface ptr back to the class type it came from involves getting the correct offset to subtract from it from the object.Interface entry at vtbl[0]. Adjustor thunks are created and pointers to them stored in the method entries in the vtbl[] in order to set the this pointer to the start of the object instance corresponding to the implementing method.

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@ghost ghost May 8, 2023 •
edited by ghost
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No interface involved here. this is still the same, I mean interpreted as opaque pointers for example, in both cases.

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if it's safe to do a bitcast, I trust the compiler to do it here (possibly only with optimization enabled) instead. I don't want to rely on the ABI internals for this

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@ghost ghost May 8, 2023 •
edited by ghost
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The compiler can't do it for you here as obviously the type of the parameter is of a base node. So to conclude, I won't insist more but at least you are aware of the issue now.

{
case 1: visit(cast(AddExpression) n); break;
case 2: visit(cast(AndAndExpression) n); break;
Expand Down Expand Up @@ -383,11 +404,15 @@ template visitIfNotNull(fields ...)
{
static if (typeof(fields[0]).stringof[$ - 2 .. $] == "[]")
{
static if (__traits(hasMember, typeof(fields[0][0]), "classinfo"))
static if (__traits(isAbstractClass, typeof(fields[0][0])))
immutable visitIfNotNull = "foreach (i; " ~ fields[0].stringof ~ ") if (i !is null) visitor.dynamicDispatch(i);\n";
else static if (__traits(hasMember, typeof(fields[0][0]), "classinfo"))
immutable visitIfNotNull = "foreach (i; " ~ fields[0].stringof ~ ") if (i !is null) visitor.visit(i);\n";
else
immutable visitIfNotNull = "foreach (i; " ~ fields[0].stringof ~ ") visitor.visit(i);\n";
}
else static if (__traits(isAbstractClass, typeof(fields[0])))
immutable visitIfNotNull = "if (" ~ fields[0].stringof ~ " !is null) visitor.dynamicDispatch(" ~ fields[0].stringof ~ ");\n";
else static if (__traits(hasMember, typeof(fields[0]), "classinfo"))
immutable visitIfNotNull = "if (" ~ fields[0].stringof ~ " !is null) visitor.visit(" ~ fields[0].stringof ~ ");\n";
else static if (is(Unqual!(typeof(fields[0])) == Token))
Expand Down
76 changes: 38 additions & 38 deletions src/dparse/astprinter.d
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Original file line number Diff line number Diff line change
Expand Up @@ -23,12 +23,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<addExpression operator=\"", str(addExpression.operator), "\">");
output.writeln("<left>");
visit(addExpression.left);
dynamicDispatch(addExpression.left);
output.writeln("</left>");
if (addExpression.right !is null)
{
output.writeln("<right>");
visit(addExpression.right);
dynamicDispatch(addExpression.right);
output.writeln("</right>");
}
output.writeln("</addExpression>");
Expand Down Expand Up @@ -58,12 +58,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<andAndExpression>");
output.writeln("<left>");
visit(andAndExpression.left);
dynamicDispatch(andAndExpression.left);
output.writeln("</left>");
if (andAndExpression.right !is null)
{
output.writeln("<right>");
visit(andAndExpression.right);
dynamicDispatch(andAndExpression.right);
output.writeln("</right>");
}
output.writeln("</andAndExpression>");
Expand All @@ -73,12 +73,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<andExpression>");
output.writeln("<left>");
visit(andExpression.left);
dynamicDispatch(andExpression.left);
output.writeln("</left>");
if (andExpression.right !is null)
{
output.writeln("<right>");
visit(andExpression.right);
dynamicDispatch(andExpression.right);
output.writeln("</right>");
}
output.writeln("</andExpression>");
Expand Down Expand Up @@ -191,13 +191,13 @@ class XMLPrinter : ASTVisitor
if (caseRangeStatement.low !is null)
{
output.writeln("<low>");
visit(caseRangeStatement.low);
dynamicDispatch(caseRangeStatement.low);
output.writeln("</low>");
}
if (caseRangeStatement.high !is null)
{
output.writeln("<high>");
visit(caseRangeStatement.high);
dynamicDispatch(caseRangeStatement.high);
output.writeln("</high>");
}
if (caseRangeStatement.declarationsAndStatements !is null)
Expand Down Expand Up @@ -295,7 +295,7 @@ class XMLPrinter : ASTVisitor
if (deprecated_.assignExpression !is null)
{
output.writeln("<deprecated>");
visit(deprecated_.assignExpression);
dynamicDispatch(deprecated_.assignExpression);
output.writeln("</deprecated>");
}
else
Expand All @@ -320,7 +320,7 @@ class XMLPrinter : ASTVisitor
visit(enumMember.type);
output.write("<name>", enumMember.name.text, "</name>");
if (enumMember.assignExpression !is null)
visit(enumMember.assignExpression);
dynamicDispatch(enumMember.assignExpression);
output.writeln("</anonymousEnumMember>");
}

Expand All @@ -336,10 +336,10 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<equalExpression operator=\"", str(equalExpression.operator), "\">");
output.writeln("<left>");
visit(equalExpression.left);
dynamicDispatch(equalExpression.left);
output.writeln("</left>");
output.writeln("<right>");
visit(equalExpression.right);
dynamicDispatch(equalExpression.right);
output.writeln("</right>");
output.writeln("</equalExpression>");
}
Expand Down Expand Up @@ -475,10 +475,10 @@ class XMLPrinter : ASTVisitor
else
output.writeln("<identityExpression operator=\"is\">");
output.writeln("<left>");
visit(identityExpression.left);
dynamicDispatch(identityExpression.left);
output.writeln("</left>");
output.writeln("<right>");
visit(identityExpression.right);
dynamicDispatch(identityExpression.right);
output.writeln("</right>");
output.writeln("</identityExpression>");
}
Expand Down Expand Up @@ -541,10 +541,10 @@ class XMLPrinter : ASTVisitor
else
output.writeln("<inExpression operator=\"in\">");
output.writeln("<left>");
visit(inExpression.left);
dynamicDispatch(inExpression.left);
output.writeln("</left>");
output.writeln("<right>");
visit(inExpression.right);
dynamicDispatch(inExpression.right);
output.writeln("</right>");
output.writeln("</inExpression>");
}
Expand Down Expand Up @@ -613,10 +613,10 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<keyValuePair>");
output.writeln("<key>");
visit(keyValuePair.key);
dynamicDispatch(keyValuePair.key);
output.writeln("</key>");
output.writeln("<value>");
visit(keyValuePair.value);
dynamicDispatch(keyValuePair.value);
output.writeln("</value>");
output.writeln("</keyValuePair>");
}
Expand Down Expand Up @@ -676,12 +676,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<mulExpression operator=\"", str(mulExpression.operator), "\">");
output.writeln("<left>");
visit(mulExpression.left);
dynamicDispatch(mulExpression.left);
output.writeln("</left>");
if (mulExpression.right !is null)
{
output.writeln("<right>");
visit(mulExpression.right);
dynamicDispatch(mulExpression.right);
output.writeln("</right>");
}
output.writeln("</mulExpression>");
Expand All @@ -691,12 +691,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<orOrExpression>");
output.writeln("<left>");
visit(orOrExpression.left);
dynamicDispatch(orOrExpression.left);
output.writeln("</left>");
if (orOrExpression.right !is null)
{
output.writeln("<right>");
visit(orOrExpression.right);
dynamicDispatch(orOrExpression.right);
output.writeln("</right>");
}
output.writeln("</orOrExpression>");
Expand Down Expand Up @@ -727,12 +727,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<powExpression>");
output.writeln("<left>");
visit(powExpression.left);
dynamicDispatch(powExpression.left);
output.writeln("</left>");
if (powExpression.right !is null)
{
output.writeln("<right>");
visit(powExpression.right);
dynamicDispatch(powExpression.right);
output.writeln("</right>");
}
output.writeln("</powExpression>");
Expand All @@ -743,10 +743,10 @@ class XMLPrinter : ASTVisitor
output.writeln("<relExpression operator=\"",
xmlAttributeEscape(str(relExpression.operator)), "\">");
output.writeln("<left>");
visit(relExpression.left);
dynamicDispatch(relExpression.left);
output.writeln("</left>");
output.writeln("<right>");
visit(relExpression.right);
dynamicDispatch(relExpression.right);
output.writeln("</right>");
output.writeln("</relExpression>");
}
Expand All @@ -768,10 +768,10 @@ class XMLPrinter : ASTVisitor
output.writeln("<shiftExpression operator=\"",
xmlAttributeEscape(str(shiftExpression.operator)), "\">");
output.writeln("<left>");
visit(shiftExpression.left);
dynamicDispatch(shiftExpression.left);
output.writeln("</left>");
output.writeln("<right>");
visit(shiftExpression.right);
dynamicDispatch(shiftExpression.right);
output.writeln("</right>");
output.writeln("</shiftExpression>");
}
Expand Down Expand Up @@ -804,7 +804,7 @@ class XMLPrinter : ASTVisitor
if (templateAliasParameter.colonExpression !is null)
{
output.writeln("<specialization>");
visit(templateAliasParameter.colonExpression);
dynamicDispatch(templateAliasParameter.colonExpression);
output.writeln("</specialization>");
}
else if (templateAliasParameter.colonType !is null)
Expand All @@ -817,7 +817,7 @@ class XMLPrinter : ASTVisitor
if (templateAliasParameter.assignExpression !is null)
{
output.writeln("<default>");
visit(templateAliasParameter.assignExpression);
dynamicDispatch(templateAliasParameter.assignExpression);
output.writeln("</default>");
}
else if (templateAliasParameter.assignType !is null)
Expand Down Expand Up @@ -962,14 +962,14 @@ class XMLPrinter : ASTVisitor
if (typeSuffix.high !is null)
{
output.writeln("<low>");
visit(typeSuffix.low);
dynamicDispatch(typeSuffix.low);
output.writeln("</low>");
output.writeln("<high>");
visit(typeSuffix.high);
dynamicDispatch(typeSuffix.high);
output.writeln("</high>");
}
else
visit(typeSuffix.low);
dynamicDispatch(typeSuffix.low);
output.writeln("</typeSuffix>");
}
}
Expand Down Expand Up @@ -1041,12 +1041,12 @@ class XMLPrinter : ASTVisitor
{
output.writeln("<xorExpression>");
output.writeln("<left>");
visit(xorExpression.left);
dynamicDispatch(xorExpression.left);
output.writeln("</left>");
if (xorExpression.right !is null)
{
output.writeln("<right>");
visit(xorExpression.right);
dynamicDispatch(xorExpression.right);
output.writeln("</right>");
}
output.writeln("</xorExpression>");
Expand All @@ -1058,15 +1058,15 @@ class XMLPrinter : ASTVisitor
if (index.high)
{
output.writeln("<low>");
visit(index.low);
dynamicDispatch(index.low);
output.writeln("</low>");

output.writeln("<high>");
visit(index.high);
dynamicDispatch(index.high);
output.writeln("</high>");
}
else
visit(index.low);
dynamicDispatch(index.low);
output.writeln("</index>");
}

Expand Down