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HLSL: 1) Implement lookahead buffers/stacks for token advance/recede, 2) use it for cast operation.

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The grammar now accepts type casts, like "(int)x", but that
has to be disambiguated from "(a + b)", needed deeper lookahead
and backing up than what existed so far.
This commit is contained in:
John Kessenich
2016-06-03 16:55:49 -06:00
parent 080cdc1737
commit 1cc1a2813e
7 changed files with 190 additions and 8 deletions
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42
hlsl/hlslGrammar.cpp
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@@ -602,7 +602,8 @@ bool HlslGrammar::acceptBinaryExpression(TIntermTyped*& node, PrecedenceLevel pr
}
// unary_expression
// : + unary_expression
// : (type) unary_expression
// | + unary_expression
// | - unary_expression
// | ! unary_expression
// | ~ unary_expression
@@ -612,9 +613,46 @@ bool HlslGrammar::acceptBinaryExpression(TIntermTyped*& node, PrecedenceLevel pr
//
bool HlslGrammar::acceptUnaryExpression(TIntermTyped*& node)
{
// (type) unary_expression
// Have to look two steps ahead, because this could be, e.g., a
// postfix_expression instead, since that also starts with at "(".
if (acceptTokenClass(EHTokLeftParen)) {
TType castType;
if (acceptType(castType)) {
if (! acceptTokenClass(EHTokRightParen)) {
expected("right parenthesis");
return false;
}
// We've matched "(type)" now, get the expression to cast
TSourceLoc loc = token.loc;
if (! acceptUnaryExpression(node))
return false;
// Hook it up like a constructor
TFunction* constructorFunction = parseContext.handleConstructorCall(loc, castType);
if (constructorFunction == nullptr) {
expected("type that can be constructed");
return false;
}
TIntermTyped* arguments = nullptr;
parseContext.handleFunctionArgument(constructorFunction, arguments, node);
node = parseContext.handleFunctionCall(loc, constructorFunction, arguments);
return true;
} else {
// This isn't a type cast, but it still started "(", so if it is a
// unary expression, it can only be a postfix_expression, so try that.
// Back it up first.
recedeToken();
return acceptPostfixExpression(node);
}
}
// peek for "op unary_expression"
TOperator unaryOp = HlslOpMap::preUnary(peek());
// postfix_expression
// postfix_expression (if no unary operator)
if (unaryOp == EOpNull)
return acceptPostfixExpression(node);