From 25738bb9c75f94b451201acfd6bcab13bdeee512 Mon Sep 17 00:00:00 2001
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From: Roy Li <rongqing.li@windriver.com>
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Date: Thu, 5 May 2016 09:52:01 +0800
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Subject: [PATCH] [PATCH] avoid gcc optimize-away the loops
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Upstream-Status: pending
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Change expression used in do_integer_mul and do_uint64_mul
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benchmarks so GCC doesn't optimize-away the loops, other
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things are same:
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- TEN(r *= s;); r -= t;
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+ i = 0;
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+ while ( i++ < 10)
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+ r *= s;
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+ r -= t;
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and TEN is macro:
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#define TEN(a) a a a a a a a a a a
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Signed-off-by: Roy Li <rongqing.li@windriver.com>
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---
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src/lat_ops.c | 30 +++++++++++++++++++++++++-----
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1 file changed, 25 insertions(+), 5 deletions(-)
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diff --git a/src/lat_ops.c b/src/lat_ops.c
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index d343ff3..457072b 100644
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--- a/src/lat_ops.c
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+++ b/src/lat_ops.c
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@@ -126,11 +126,23 @@ do_integer_mul(iter_t iterations, void* cookie)
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struct _state *pState = (struct _state*)cookie;
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register int r = pState->N + 37431;
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register int s = pState->N + 4;
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- register int t = r * s * s * s * s * s * s * s * s * s * s - r;
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+ register int t = r;
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+ int i = 0;
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+
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+ while ( i++ < 10)
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+ t *= s;
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+ t -= r;
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while (iterations-- > 0) {
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- TEN(r *= s;); r -= t;
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- TEN(r *= s;); r -= t;
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+ i = 0;
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+ while ( i++ < 10)
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+ r *= s;
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+ r -= t;
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+
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+ i = 0;
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+ while ( i++ < 10)
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+ r *= s;
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+ r -= t;
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}
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use_int(r);
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}
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@@ -207,13 +219,21 @@ do_int64_mul(iter_t iterations, void* cookie)
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register int64 r = (int64)pState->N + 37420;
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register int64 s = (int64)pState->N + 4;
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register int64 t;
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+ int i = 0;
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r += (int64)(pState->N + 6)<<32;
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t = r * s * s * s * s * s * s * s * s * s * s - r;
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while (iterations-- > 0) {
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- TEN(r *= s;); r -= t;
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- TEN(r *= s;); r -= t;
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+ i = 0;
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+ while ( i++ < 10)
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+ r *= s;
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+ r -= t;
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+
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+ i = 0;
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+ while ( i++ < 10)
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+ r *= s;
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+ r -= t;
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}
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use_int((int)r);
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}
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