tree ebcfbc4dc1687a7007bcb48618be97fbee171581
parent 1d59aa07776ee6c95804e282cee1e79709b7313b
author qining <qining@google.com> 1470331448 -0400
committer qining <qining@google.com> 1472475533 -0400

Fold spec constants to normal constants (values fixed)

For the spec constants defined by OpSpecConstantOp and
OpSpecContantComposite, if all of their operands are constants with
determined values (normal constants whose values are fixed), calculate
the correct values of the spec constants and re-define them as normal
constants.

In short, this pass replaces all the spec constants defined by
OpSpecContantOp and OpSpecConstantComposite with normal constants when
possible. So far not all valid operations of OpSpecConstantOp are
supported, we have several constriction here:

1) Only 32-bit integer and boolean (both scalar and vector) are
supported for any arithmetic operations. Integers in other width (like
64-bit) are not supported.
2) OpSConvert, OpFConvert, OpQuantizeToF16, and all the
operations under Kernel capability, are not supported.
3) OpCompositeInsert is not supported.

Note that this pass does not unify normal constants. This means it is
possible to have new generatd constants defining the same values.