Re: [LTO][PATCH] Delete temporary ltrans output files

[Diego Novillo <dnovillo at google dot com>]

Temporary file handling needs  to be cleaned up.  We've been
using and -Wl,-debug WPA_SAVE_LTRANS as a quick hack, but it's
too confusing, there should be a single mechanism for all this.

I propose that we use -save-temps to preserve *every* temporary
file.

The flow of processes and temporary files is something like this:

$ gcc -fwhopr -save-temps -o a a.o b.o
    -> collect2 -fwhopr [various-flags] -o a a.o b.o
      -> lto-wrapper gcc/xgcc -fwhopr -save-temps -o a a.o b.o
	-> lto1 -fwpa a.o b.o ...
	    -> ltrans-driver (reads -save-temps from CFLAGS)
		-> lto1 -fno-wpa -fltrans a.o -o <tmp>.lto.ltrans.o
		-> lto1 -fno-wpa -fltrans b.o -o <tmp>.lto.ltrans.o


We may need to interpret -save-temps in lto1 to preserve
temporary files.

Another thing I would like to do at some point is to have a
better naming convention for the WPA and LTRANS object files and
dumpbases, the random strings are impossible to link back to the
original source files.


Thoughts?


Diego.