why is spru187t.pdf TMS320C6000 Optimizing Compiler v 7.3 User's Guide (Rev. T) no more downloadable

This link http://www.ti.com/lit/pdf/spru187 will get you the latest revision of the C6000 compiler book, whatever that is.  That's the best link to use.  Anything else is subject to going stale over time.  The books are also part of the compiler installation, in the \doc directory.  A typical path looks like:

C:\Program Files\Texas Instruments\ccsv5\tools\compiler\c6000\doc\SPRU187T.pdf

That is the best way to get the book for a specific version of the compiler.

Thanks and regards,

-George