FS#19386 - [gcc] Possible bug regarding processor capabilities detection.
Attached to Project:
Arch Linux
Opened by James (JRMoore) - Friday, 07 May 2010, 18:36 GMT
Last edited by Allan McRae (Allan) - Monday, 10 May 2010, 11:23 GMT
Opened by James (JRMoore) - Friday, 07 May 2010, 18:36 GMT
Last edited by Allan McRae (Allan) - Monday, 10 May 2010, 11:23 GMT
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Details
Hello, I'm using the current version of the gcc package
(4.5.0-1) in an Intel Core2 Duo T7300 @ 2.00GHz.
Running "gcc -Q -march=native --help=target" generates the following output: http://pastebin.com/hn1VS0Kw I can see there that the architecture is detected correctly (core2 for march and mtune) but all SSE capabilities are disabled. As far as I know my processor supports up to SSSE3, so SSE, SSE2, SSE3 and SSSE3 at least should be enabled as well as MMX. Am I missing something or might there be a problem with the binaries in the current package? |
This task depends upon
Closed by Allan McRae (Allan)
Monday, 10 May 2010, 11:23 GMT
Reason for closing: Upstream
Additional comments about closing: see comments
Monday, 10 May 2010, 11:23 GMT
Reason for closing: Upstream
Additional comments about closing: see comments
and http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43718 - so proabably the SSE settings are well applied but badly displayed with -Q --help-target.
I've checked the binaries in Fedora as well, with the same results. Maybe it's related to the upstream bugs Andreas mentioned, is there any way to know if SSE instructions are being used anyway?
gcc -march=native -S -fverbose-asm hello.c
and look in the header of the resulting hello.s file.
Furthermore if compiling with -mfpmath=sse it does the appropriate, otherwise GCC would issue the following warning: "SSE instruction set disabled, using 387 arithmetics"