From: Florian Krohm Date: Wed, 4 Jan 2012 01:34:53 +0000 (+0000) Subject: Add a comment about setting aside a register for VG_(dispatch_ctr) X-Git-Tag: svn/VALGRIND_3_8_1^2~222 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fdb24e7727ea9356a4ffefacd352d6217ac7cba1;p=thirdparty%2Fvalgrind.git Add a comment about setting aside a register for VG_(dispatch_ctr) on s390. git-svn-id: svn://svn.valgrind.org/vex/trunk@2236 --- diff --git a/VEX/priv/host_s390_defs.c b/VEX/priv/host_s390_defs.c index ad589e785a..f086e55d75 100644 --- a/VEX/priv/host_s390_defs.c +++ b/VEX/priv/host_s390_defs.c @@ -144,7 +144,12 @@ s390_hreg_get_allocable(Int *nregs, HReg **arr) Otherwise, they are available to the allocator */ (*arr)[i++] = mkHReg(10, HRcInt64, False); (*arr)[i++] = mkHReg(11, HRcInt64, False); - /* GPR12 is not available because it caches VG_(dispatch_ctr) */ + /* GPR12 is not available because it caches VG_(dispatch_ctr). + Setting aside a register for the counter gives slightly better + performance - most of the time. From the 10 tests in "make perf" + 8 run faster with a max observed speedup of 2.6% for bz2. ffbench + is the counter example. It runs 1.3% faster without the dedicated + register. */ /* GPR13 is not available because it is used as guest state pointer */ /* GPR14 is not available because it is used as link register */ /* GPR15 is not available because it is used as stack pointer */