Assert exp2 is exact at integer values
Assert exp2 is exact at integer values

The Vulkan spec doesn't spell out this requirement, but it is expected
by dEQP-VK that integer inputs to exp2 produce exact results.

Both the new Exp2(), and Exp2_legacy(), pass this assertion (but the
latter does not pass MathTest.Exp2Exhaustive as a whole).

Bug: b/169754022
Change-Id: I0534aad6e1dd0c68d1b695646b46e0ee5d949681
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/63169
Kokoro-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>

google/swiftshader,google/swiftshader,google/swiftshader