Replace divides by small values with multiplies.

This ports the OD_DIVU_SMALL code from Daala to AOM so that divides by
 constants smaller than OD_DIVU_DMAX (1024) are done using a multiply.
Added a unit test for OD_DIVU_SMALL in test/divu_small_test.cc.

Change-Id: Id9fee172d54477355571c5d6c12c584fb65769e5

test/acm_random.h

@@ -24,6 +24,11 @@ class ACMRandom {
   explicit ACMRandom(int seed) : random_(seed) {}
 
   void Reset(int seed) { random_.Reseed(seed); }
+
+  uint32_t Rand31(void) {
+    return random_.Generate(testing::internal::Random::kMaxRange);
+  }
+
   uint16_t Rand16(void) {
     const uint32_t value =
         random_.Generate(testing::internal::Random::kMaxRange);

test/divu_small_test.cc

+/*Daala video codec
+Copyright (c) 2013 Daala project contributors.  All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+- Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+- Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS”
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.*/
+
+#include <stdlib.h>
+
+#include "third_party/googletest/src/include/gtest/gtest.h"
+
+#include "test/acm_random.h"
+#include "vp10/common/odintrin.h"
+
+using libvpx_test::ACMRandom;
+
+TEST(Daala, TestDIVUuptoMAX) {
+  for (int d = 1; d <= OD_DIVU_DMAX; d++) {
+    for (uint32_t x = 1; x <= 1000000; x++) {
+      GTEST_ASSERT_EQ(x/d, OD_DIVU_SMALL(x, d)) << "x=" << x << " d=" << d <<
+       " x/d=" << (x/d) << " != " << OD_DIVU_SMALL(x, d);
+    }
+  }
+}
+
+TEST(Daala, TestDIVUrandI31) {
+  ACMRandom rnd(ACMRandom::DeterministicSeed());
+  for (int d = 1; d < OD_DIVU_DMAX; d++) {
+    for (int i = 0; i < 1000000; i++) {
+      uint32_t x = rnd.Rand31();
+      GTEST_ASSERT_EQ(x/d, OD_DIVU_SMALL(x, d)) << "x=" << x << " d=" << d <<
+       " x/d=" << (x/d) << " != " << OD_DIVU_SMALL(x, d);
+    }
+  }
+}

test/test.mk

@@ -92,6 +92,7 @@ LIBVPX_TEST_SRCS-yes                   += partial_idct_test.cc
 LIBVPX_TEST_SRCS-yes                   += superframe_test.cc
 LIBVPX_TEST_SRCS-yes                   += tile_independence_test.cc
 LIBVPX_TEST_SRCS-yes                   += boolcoder_test.cc
+LIBVPX_TEST_SRCS-yes                   += divu_small_test.cc
 LIBVPX_TEST_SRCS-yes                   += encoder_parms_get_to_decoder.cc
 endif
 

vp10/common/odintrin.h

@@ -19,7 +19,18 @@ typedef int od_coeff;
 
 typedef int16_t od_dering_in;
 
-#define OD_DIVU_SMALL(_x, _d) ((_x) / (_d))
+# define OD_DIVU_DMAX (1024)
+
+extern uint32_t OD_DIVU_SMALL_CONSTS[OD_DIVU_DMAX][2];
+
+/*Translate unsigned division by small divisors into multiplications.*/
+# define OD_DIVU_SMALL(_x, _d) \
+  ((uint32_t)((OD_DIVU_SMALL_CONSTS[(_d)-1][0]* \
+  (uint64_t)(_x)+OD_DIVU_SMALL_CONSTS[(_d)-1][1])>>32)>> \
+  (OD_ILOG(_d)-1))
+
+# define OD_DIVU(_x, _d) \
+  (((_d) < OD_DIVU_DMAX)?(OD_DIVU_SMALL((_x), (_d))):((_x)/(_d)))
 
 #define OD_MINI VPXMIN
 #define OD_CLAMPI(min, val, max) clamp((val), (min), (max))

vp10/vp10_common.mk

@@ -67,8 +67,9 @@ VP10_COMMON_SRCS-yes += common/od_dering.c
 VP10_COMMON_SRCS-yes += common/od_dering.h
 VP10_COMMON_SRCS-yes += common/dering.c
 VP10_COMMON_SRCS-yes += common/dering.h
-VP10_COMMON_SRCS-yes += common/odintrin.h
 endif
+VP10_COMMON_SRCS-yes += common/odintrin.c
+VP10_COMMON_SRCS-yes += common/odintrin.h
 
 ifneq ($(CONFIG_VPX_HIGHBITDEPTH),yes)
 VP10_COMMON_SRCS-$(HAVE_DSPR2)  += common/mips/dspr2/itrans4_dspr2.c