Patrick Williams | b48b7b4 | 2016-08-17 15:04:38 -0500 | [diff] [blame^] | 1 | [PATCH] avoid gcc optimize-away the loops |
| 2 | |
| 3 | Upstream-Status: pending |
| 4 | |
| 5 | Change expression used in do_integer_mul and do_uint64_mul |
| 6 | benchmarks so GCC doesn't optimize-away the loops, other |
| 7 | things are same: |
| 8 | - TEN(r *= s;); r -= t; |
| 9 | + i = 0; |
| 10 | + while ( i++ < 10) |
| 11 | + r *= s; |
| 12 | + r -= t; |
| 13 | |
| 14 | and TEN is macro: |
| 15 | #define TEN(a) a a a a a a a a a a |
| 16 | |
| 17 | Signed-off-by: Roy Li <rongqing.li@windriver.com> |
| 18 | --- |
| 19 | src/lat_ops.c | 30 +++++++++++++++++++++++++----- |
| 20 | 1 file changed, 25 insertions(+), 5 deletions(-) |
| 21 | |
| 22 | diff --git a/src/lat_ops.c b/src/lat_ops.c |
| 23 | index d343ff3..457072b 100644 |
| 24 | --- a/src/lat_ops.c |
| 25 | +++ b/src/lat_ops.c |
| 26 | @@ -126,11 +126,23 @@ do_integer_mul(iter_t iterations, void* cookie) |
| 27 | struct _state *pState = (struct _state*)cookie; |
| 28 | register int r = pState->N + 37431; |
| 29 | register int s = pState->N + 4; |
| 30 | - register int t = r * s * s * s * s * s * s * s * s * s * s - r; |
| 31 | + register int t = r; |
| 32 | + int i = 0; |
| 33 | + |
| 34 | + while ( i++ < 10) |
| 35 | + t *= s; |
| 36 | + t -= r; |
| 37 | |
| 38 | while (iterations-- > 0) { |
| 39 | - TEN(r *= s;); r -= t; |
| 40 | - TEN(r *= s;); r -= t; |
| 41 | + i = 0; |
| 42 | + while ( i++ < 10) |
| 43 | + r *= s; |
| 44 | + r -= t; |
| 45 | + |
| 46 | + i = 0; |
| 47 | + while ( i++ < 10) |
| 48 | + r *= s; |
| 49 | + r -= t; |
| 50 | } |
| 51 | use_int(r); |
| 52 | } |
| 53 | @@ -207,13 +219,21 @@ do_int64_mul(iter_t iterations, void* cookie) |
| 54 | register int64 r = (int64)pState->N + 37420; |
| 55 | register int64 s = (int64)pState->N + 4; |
| 56 | register int64 t; |
| 57 | + int i = 0; |
| 58 | |
| 59 | r += (int64)(pState->N + 6)<<32; |
| 60 | t = r * s * s * s * s * s * s * s * s * s * s - r; |
| 61 | |
| 62 | while (iterations-- > 0) { |
| 63 | - TEN(r *= s;); r -= t; |
| 64 | - TEN(r *= s;); r -= t; |
| 65 | + i = 0; |
| 66 | + while ( i++ < 10) |
| 67 | + r *= s; |
| 68 | + r -= t; |
| 69 | + |
| 70 | + i = 0; |
| 71 | + while ( i++ < 10) |
| 72 | + r *= s; |
| 73 | + r -= t; |
| 74 | } |
| 75 | use_int((int)r); |
| 76 | } |
| 77 | -- |
| 78 | 2.8.1 |
| 79 | |