scripts: add stackusage script

The current checkstack.pl script has a few problems, stemming from the overly simplistic attempt at parsing objdump output with regular expressions: For example, on x86_64 it doesn't take the push instruction into account, making it consistently underestimate the real stack use, and it also doesn't capture stack pointer adjustments of exactly 128 bytes [1]. Since newer gcc (>= 4.6) knows about -fstack-usage, we might as well take the information straight from the horse's mouth. This patch introduces scripts/stackusage, which is a simple wrapper for running make with KCFLAGS set to -fstack-usage. Example use is scripts/stackusage -o out.su -j8 lib/ The script understands "-o foo" for writing to 'foo' and -h for a trivial help text; anything else is passed to make. Afterwards, we find all newly created .su files, massage them a little, sort by stack use and write the result to a single output file. Note that the function names printed by (at least) gcc 4.7 are sometimes useless. For example, the first three lines of out.su generated above are ./lib/decompress_bunzip2.c:155 get_next_block 448 static ./lib/decompress_unlzma.c:537 unlzma 336 static ./lib/vsprintf.c:616 8 304 static That function '8' is really the static symbol_string(), but it has been subject to 'interprocedural scalar replacement of aggregates', so its name in the object file is 'symbol_string.isra.8'. gcc 5.0 doesn't have this problem; it uses the full name as seen in the object file. [1] Since gcc encodes that by 48 83 c4 80 add $0xffffffffffffff80,%rsp and not 48 81 ec 80 00 00 00 sub $0x80,%rsp since -128 fits in an imm8.

RVRasmus Villemoes committed 11 years ago