kc3-lang/angle

2018-01-04T17:09:11

Constant fold array indexing and comparison A virtual function to get the constant value of an AST node is added to TIntermTyped. This way a constant value can be retrieved conveniently from multiple different types of nodes. TIntermSymbol nodes pointing to a const variable can return the value associated with the variable, constructor nodes can build a constant value from their arguments, and indexing nodes can index into a constant array. This enables constant folding operations on constant arrays, while making sure that large amounts of data are not duplicated in the output shader. When folding an operation makes sense, the values of the arguments can be retrieved by using the new TIntermTyped::getConstantValue(). When folding an operation would result in duplicating data, the AST can just be left to be written out as is. For example, if the code contains a constant array of arrays, indexing into individual elements of the inner arrays can be folded, but indexing the top level array is left in place and not replaced with duplicated array literals. Constant folding is supported for indexing and comparisons of arrays. In case constant arrays are only referenced through foldable operations, the variable declarations will be pruned from the AST by the RemoveUnreferencedVariables step. BUG=angleproject:2298 TEST=angle_unittests Change-Id: I5b3be237b7e9fdba56aa9bf0a41b691f4d8f01eb Reviewed-on: https://chromium-review.googlesource.com/850973 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>