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lmbench: avoid gcc optimize-away multiplication

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Change expression used in do_integer_mul and do_uint64_mul
benchmarks so GCC doesn't optimize-away the loops,

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
This commit is contained in:
Roy Li 2016-05-05 09:52:01 +08:00 committed by Armin Kuster
parent 1726e7172b
commit e341fa03f0
2 changed files with 80 additions and 0 deletions
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79
meta-oe/recipes-benchmark/lmbench/lmbench/0001-avoid-gcc-optimize-away-the-loops.patch Normal file
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@ -0,0 +1,79 @@
[PATCH] avoid gcc optimize-away the loops
Upstream-Status: pending
Change expression used in do_integer_mul and do_uint64_mul
benchmarks so GCC doesn't optimize-away the loops, other
things are same:
- TEN(r *= s;); r -= t;
+ i = 0;
+ while ( i++ < 10)
+ r *= s;
+ r -= t;
and TEN is macro:
#define TEN(a) a a a a a a a a a a
Signed-off-by: Roy Li <rongqing.li@windriver.com>
---
src/lat_ops.c | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)
diff --git a/src/lat_ops.c b/src/lat_ops.c
index d343ff3..457072b 100644
--- a/src/lat_ops.c
+++ b/src/lat_ops.c
@@ -126,11 +126,23 @@ do_integer_mul(iter_t iterations, void* cookie)
struct _state *pState = (struct _state*)cookie;
register int r = pState->N + 37431;
register int s = pState->N + 4;
- register int t = r * s * s * s * s * s * s * s * s * s * s - r;
+ register int t = r;
+ int i = 0;
+
+ while ( i++ < 10)
+ t *= s;
+ t -= r;
while (iterations-- > 0) {
- TEN(r *= s;); r -= t;
- TEN(r *= s;); r -= t;
+ i = 0;
+ while ( i++ < 10)
+ r *= s;
+ r -= t;
+
+ i = 0;
+ while ( i++ < 10)
+ r *= s;
+ r -= t;
}
use_int(r);
}
@@ -207,13 +219,21 @@ do_int64_mul(iter_t iterations, void* cookie)
register int64 r = (int64)pState->N + 37420;
register int64 s = (int64)pState->N + 4;
register int64 t;
+ int i = 0;
r += (int64)(pState->N + 6)<<32;
t = r * s * s * s * s * s * s * s * s * s * s - r;
while (iterations-- > 0) {
- TEN(r *= s;); r -= t;
- TEN(r *= s;); r -= t;
+ i = 0;
+ while ( i++ < 10)
+ r *= s;
+ r -= t;
+
+ i = 0;
+ while ( i++ < 10)
+ r *= s;
+ r -= t;
}
use_int((int)r);
}
--
2.8.1

1
meta-oe/recipes-benchmark/lmbench/lmbench_3.0-a9.bb
View File

@ -18,6 +18,7 @@ SRC_URI = "${SOURCEFORGE_MIRROR}/lmbench/lmbench-${PV}.tgz \
file://use-base_libdir-instead-of-hardcoded-lib.patch \
file://lmbench_result_html_report.patch \
file://fix-lmbench-memory-check-failure.patch \
file://0001-avoid-gcc-optimize-away-the-loops.patch \
"
SRC_URI[md5sum] = "b3351a3294db66a72e2864a199d37cbf"
SRC_URI[sha256sum] = "cbd5777d15f44eab7666dcac418054c3c09df99826961a397d9acf43d8a2a551"