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From 25738bb9c75f94b451201acfd6bcab13bdeee512 Mon Sep 17 00:00:00 2001
From: Roy Li <rongqing.li@windriver.com>
Date: Thu, 5 May 2016 09:52:01 +0800
Subject: [PATCH] [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);
}
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