swift234

Make minus sign part of IntegerLiteralExpr and make integers literals 136-bits
wide

Currently integer literals are 64-bit.  In order to allow checking for overflow
while converting an integer literal to swift.UInt/Int* types we need at least
65 bits.  But floating point numbers (Float32, Float64, Float80) are
BuiltinIntegerLiteralConvertible.  In order to allow spelling large floating
point constants, we allow 136-bit literals.

Rationale: 128 bits are enough to represent the absolute value of min/max IEEE
Binary32, and we need 1 bit to represent the sign.  136 is 129 rounded to the
next 8 bits.

The plan is to have builtins that do the overflow check and convert 136-bit
numbers to the required width.  We need these builtins for both integers and
floating point numbers to ensure that 136-bit numbers are folded into sane
constants in SIL and don’t escape to LLVM IR.


Swift SVN r9253