kc3-lang/angle

2016-09-27T11:15:38

Fix handling integer overflow in constant folding Integer operations that overflow are defined to wrap in the ESSL 3.00.6 spec. Constant folding that happens inside the shader translator should also follow the wrapping rules. The new implementations of wrapping integer addition and subtraction use unsigned integers to perform calculations. Unsigned integers are defined to implement arithmetic in modulo 2^n in the C++ spec. This behavior is also leveraged to implement wrapping unsigned integer multiplication. The implementation of wrapping signed integer multiplication is slightly trickier. The operands are casted to a wider type to perform the multiplication in a way that doesn't overflow, and then the result is truncated and casted back to the narrower integer type. Incorrect tests that expected errors to be generated from integer overflow in constant folding are removed. BUG=chromium:637050 TEST=angle_unittests Change-Id: I0de7e25881d254803455fbf22907c192f49d09ff Reviewed-on: https://chromium-review.googlesource.com/390252 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org>