swift234

Revert "Revert "Reimplement integer arithmetic overflow checking to use special, error on overflow builtins""

(This only fails under -DSWIFT_OPTIMIZED=NO; most likely due to an llvm bug.)

We've decided that it's best to specialize each arithmetic builtin that could overflow, instead of calling a separate generic "staticReport" builtin and passing it enough info to produce the message. The main advantage of this approach is that it would be possible for the compiler to customize the message and better link it to the builtin that overflows. For example, the constants that participated in the computation could be printed. In addition, less code will be generated and the compiler could, in the future, automatically emit the overflow diagnostics/trap at runtime.

This patch introduces new versions of op_with_overflow swift builtins. Which are lowered to llvm.op_with_overflow builtins in IRGen after the static diagnostics. If the last argument to the builtins evaluates to true, the overflow is unintentional. CCP uses the builtins to diagnose the overflow detectable at compile time. FixedPoint is changed to rely on these in implementation of primitive arithmetic operations.

Swift SVN r9328