Checkasm: assembly testing and benchmarking tool

It provides the following features:
 * verify correctness by comparing output to the C version.
 * detect failure to save and restore clobbered callee-saved registers.
 * detect 32-bit parameters being used as if they were 64-bit in x86-64
   (the upper halves are not guaranteed to be zero - but in practice
   they very often are, which makes those bugs hard to spot otherwise).
 * easy benchmarking.

Compile by running 'make checkasm'.
Execute by running 'tests/checkasm/checkasm'.

Optional arguments are '--bench' to run benchmarks for all functions,
'--bench=<pattern>' to run benchmarks for all functions that starts with
<pattern>, and '<integer>' to seed the PRNG for reproducible results.

Contains unit tests for most h264pred functions to get started, more tests
can be added afterwards using those as a reference.

Loosely based on code from x264. Currently only supports x86 and x86-64,
but additional architectures shouldn't be too much of an obstacle to add.

Note that functions with floating point parameters or floating point
return values are not supported. Some compiler-specific features or
preprocessor hacks would likely be required to add support for that.

Signed-off-by: Janne Grunau <janne-libav@jannau.net>

8 files changed, 1086 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index d3cde42..96494aa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -46,6 +46,7 @@
 /libavutil/avconfig.h
 /tests/audiogen
 /tests/base64
+/tests/checkasm/checkasm
 /tests/data/
 /tests/pixfmts.mak
 /tests/rotozoom
diff --git a/tests/Makefile b/tests/Makefile
index ed34101..fa83ba4 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -173,5 +173,7 @@ testclean:
 
 -include $(wildcard tests/*.d)
 
+include $(SRC_PATH)/tests/checkasm/Makefile
+
 .PHONY: fate* lcov lcov-reset
 .INTERMEDIATE: coverage.info
diff --git a/tests/checkasm/Makefile b/tests/checkasm/Makefile
new file mode 100644
index 0000000..33e2c09
--- /dev/null
+++ b/tests/checkasm/Makefile
@@ -0,0 +1,33 @@
+# libavcodec tests
+AVCODECOBJS-$(CONFIG_H264PRED) += h264pred.o
+
+CHECKASMOBJS-$(CONFIG_AVCODEC) += $(AVCODECOBJS-yes)
+
+
+-include $(SRC_PATH)/tests/checkasm/$(ARCH)/Makefile
+
+CHECKASMOBJS += $(CHECKASMOBJS-yes) checkasm.o
+CHECKASMOBJS := $(sort $(CHECKASMOBJS:%=tests/checkasm/%))
+
+-include $(CHECKASMOBJS:.o=.d)
+
+CHECKASMDIRS := $(sort $(dir $(CHECKASMOBJS)))
+$(CHECKASMOBJS): | $(CHECKASMDIRS)
+OBJDIRS += $(CHECKASMDIRS)
+
+# We rely on function pointers intentionally declared without specified argument types.
+tests/checkasm/%.o: CFLAGS := $(CFLAGS:-Wstrict-prototypes=-Wno-strict-prototypes)
+
+CHECKASM := tests/checkasm/checkasm$(EXESUF)
+
+$(CHECKASM): $(EXEOBJS) $(CHECKASMOBJS) $(FF_DEP_LIBS)
+	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $(CHECKASMOBJS) $(FF_EXTRALIBS)
+
+checkasm: $(CHECKASM)
+
+clean:: checkasmclean
+
+checkasmclean:
+	$(RM) $(CHECKASM) $(CLEANSUFFIXES:%=tests/checkasm/%) $(CLEANSUFFIXES:%=tests/checkasm/$(ARCH)/%)
+
+.PHONY: checkasm
diff --git a/tests/checkasm/checkasm.c b/tests/checkasm/checkasm.c
new file mode 100644
index 0000000..59383b8
--- /dev/null
+++ b/tests/checkasm/checkasm.c
@@ -0,0 +1,484 @@
+/*
+ * Assembly testing and benchmarking tool
+ * Copyright (c) 2015 Henrik Gramner
+ * Copyright (c) 2008 Loren Merritt
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Libav; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "checkasm.h"
+#include "libavutil/common.h"
+#include "libavutil/cpu.h"
+#include "libavutil/random_seed.h"
+
+#if ARCH_X86
+#include "libavutil/x86/cpu.h"
+#endif
+
+#if HAVE_SETCONSOLETEXTATTRIBUTE
+#include <windows.h>
+#define COLOR_RED    FOREGROUND_RED
+#define COLOR_GREEN  FOREGROUND_GREEN
+#define COLOR_YELLOW (FOREGROUND_RED|FOREGROUND_GREEN)
+#else
+#define COLOR_RED    1
+#define COLOR_GREEN  2
+#define COLOR_YELLOW 3
+#endif
+
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#if !HAVE_ISATTY
+#define isatty(fd) 1
+#endif
+
+/* List of tests to invoke */
+static void (* const tests[])(void) = {
+#if CONFIG_H264PRED
+    checkasm_check_h264pred,
+#endif
+    NULL
+};
+
+/* List of cpu flags to check */
+static const struct {
+    const char *name;
+    const char *suffix;
+    int flag;
+} cpus[] = {
+#if ARCH_X86
+    { "MMX",      "mmx",      AV_CPU_FLAG_MMX|AV_CPU_FLAG_CMOV },
+    { "MMXEXT",   "mmxext",   AV_CPU_FLAG_MMXEXT },
+    { "3DNOW",    "3dnow",    AV_CPU_FLAG_3DNOW },
+    { "3DNOWEXT", "3dnowext", AV_CPU_FLAG_3DNOWEXT },
+    { "SSE",      "sse",      AV_CPU_FLAG_SSE },
+    { "SSE2",     "sse2",     AV_CPU_FLAG_SSE2|AV_CPU_FLAG_SSE2SLOW },
+    { "SSE3",     "sse3",     AV_CPU_FLAG_SSE3|AV_CPU_FLAG_SSE3SLOW },
+    { "SSSE3",    "ssse3",    AV_CPU_FLAG_SSSE3|AV_CPU_FLAG_ATOM },
+    { "SSE4.1",   "sse4",     AV_CPU_FLAG_SSE4 },
+    { "SSE4.2",   "sse42",    AV_CPU_FLAG_SSE42 },
+    { "AVX",      "avx",      AV_CPU_FLAG_AVX },
+    { "XOP",      "xop",      AV_CPU_FLAG_XOP },
+    { "FMA3",     "fma3",     AV_CPU_FLAG_FMA3 },
+    { "FMA4",     "fma4",     AV_CPU_FLAG_FMA4 },
+    { "AVX2",     "avx2",     AV_CPU_FLAG_AVX2 },
+#endif
+    { NULL }
+};
+
+typedef struct CheckasmFuncVersion {
+    struct CheckasmFuncVersion *next;
+    intptr_t (*func)();
+    int ok;
+    int cpu;
+    int iterations;
+    uint64_t cycles;
+} CheckasmFuncVersion;
+
+/* Binary search tree node */
+typedef struct CheckasmFunc {
+    struct CheckasmFunc *child[2];
+    CheckasmFuncVersion versions;
+    char name[1];
+} CheckasmFunc;
+
+/* Internal state */
+static struct {
+    CheckasmFunc *funcs;
+    CheckasmFunc *current_func;
+    CheckasmFuncVersion *current_func_ver;
+    const char *bench_pattern;
+    int bench_pattern_len;
+    int num_checked;
+    int num_failed;
+    int nop_time;
+    int cpu_flag;
+    const char *cpu_flag_name;
+} state;
+
+/* PRNG state */
+AVLFG checkasm_lfg;
+
+/* Print colored text to stderr if the terminal supports it */
+static void color_printf(int color, const char *fmt, ...)
+{
+    static int use_color = -1;
+    va_list arg;
+
+#if HAVE_SETCONSOLETEXTATTRIBUTE
+    static HANDLE con;
+    static WORD org_attributes;
+
+    if (use_color < 0) {
+        CONSOLE_SCREEN_BUFFER_INFO con_info;
+        con = GetStdHandle(STD_ERROR_HANDLE);
+        if (con && con != INVALID_HANDLE_VALUE && GetConsoleScreenBufferInfo(con, &con_info)) {
+            org_attributes = con_info.wAttributes;
+            use_color = 1;
+        } else
+            use_color = 0;
+    }
+    if (use_color)
+        SetConsoleTextAttribute(con, (org_attributes & 0xfff0) | (color & 0x0f));
+#else
+    if (use_color < 0) {
+        const char *term = getenv("TERM");
+        use_color = term && strcmp(term, "dumb") && isatty(2);
+    }
+    if (use_color)
+        fprintf(stderr, "\x1b[%d;3%dm", (color & 0x08) >> 3, color & 0x07);
+#endif
+
+    va_start(arg, fmt);
+    vfprintf(stderr, fmt, arg);
+    va_end(arg);
+
+    if (use_color) {
+#if HAVE_SETCONSOLETEXTATTRIBUTE
+        SetConsoleTextAttribute(con, org_attributes);
+#else
+        fprintf(stderr, "\x1b[0m");
+#endif
+    }
+}
+
+/* Deallocate a tree */
+static void destroy_func_tree(CheckasmFunc *f)
+{
+    if (f) {
+        CheckasmFuncVersion *v = f->versions.next;
+        while (v) {
+            CheckasmFuncVersion *next = v->next;
+            free(v);
+            v = next;
+        }
+
+        destroy_func_tree(f->child[0]);
+        destroy_func_tree(f->child[1]);
+        free(f);
+    }
+}
+
+/* Allocate a zero-initialized block, clean up and exit on failure */
+static void *checkasm_malloc(size_t size)
+{
+    void *ptr = calloc(1, size);
+    if (!ptr) {
+        fprintf(stderr, "checkasm: malloc failed\n");
+        destroy_func_tree(state.funcs);
+        exit(1);
+    }
+    return ptr;
+}
+
+/* Get the suffix of the specified cpu flag */
+static const char *cpu_suffix(int cpu)
+{
+    int i = FF_ARRAY_ELEMS(cpus);
+
+    while (--i >= 0)
+        if (cpu & cpus[i].flag)
+            return cpus[i].suffix;
+
+    return "c";
+}
+
+#ifdef AV_READ_TIME
+static int cmp_nop(const void *a, const void *b)
+{
+    return *(const uint16_t*)a - *(const uint16_t*)b;
+}
+
+/* Measure the overhead of the timing code (in decicycles) */
+static int measure_nop_time(void)
+{
+    uint16_t nops[10000];
+    int i, nop_sum = 0;
+
+    for (i = 0; i < 10000; i++) {
+        uint64_t t = AV_READ_TIME();
+        nops[i] = AV_READ_TIME() - t;
+    }
+
+    qsort(nops, 10000, sizeof(uint16_t), cmp_nop);
+    for (i = 2500; i < 7500; i++)
+        nop_sum += nops[i];
+
+    return nop_sum / 500;
+}
+
+/* Print benchmark results */
+static void print_benchs(CheckasmFunc *f)
+{
+    if (f) {
+        print_benchs(f->child[0]);
+
+        /* Only print functions with at least one assembly version */
+        if (f->versions.cpu || f->versions.next) {
+            CheckasmFuncVersion *v = &f->versions;
+            do {
+                if (v->iterations) {
+                    int decicycles = (10*v->cycles/v->iterations - state.nop_time) / 4;
+                    printf("%s_%s: %d.%d\n", f->name, cpu_suffix(v->cpu), decicycles/10, decicycles%10);
+                }
+            } while ((v = v->next));
+        }
+
+        print_benchs(f->child[1]);
+    }
+}
+#endif
+
+/* ASCIIbetical sort except preserving natural order for numbers */
+static int cmp_func_names(const char *a, const char *b)
+{
+    int ascii_diff, digit_diff;
+
+    for (; !(ascii_diff = *a - *b) && *a; a++, b++);
+    for (; av_isdigit(*a) && av_isdigit(*b); a++, b++);
+
+    return (digit_diff = av_isdigit(*a) - av_isdigit(*b)) ? digit_diff : ascii_diff;
+}
+
+/* Get a node with the specified name, creating it if it doesn't exist */
+static CheckasmFunc *get_func(const char *name, int length)
+{
+    CheckasmFunc *f, **f_ptr = &state.funcs;
+
+    /* Search the tree for a matching node */
+    while ((f = *f_ptr)) {
+        int cmp = cmp_func_names(name, f->name);
+        if (!cmp)
+            return f;
+
+        f_ptr = &f->child[(cmp > 0)];
+    }
+
+    /* Allocate and insert a new node into the tree */
+    f = *f_ptr = checkasm_malloc(sizeof(CheckasmFunc) + length);
+    memcpy(f->name, name, length+1);
+
+    return f;
+}
+
+/* Perform tests and benchmarks for the specified cpu flag if supported by the host */
+static void check_cpu_flag(const char *name, int flag)
+{
+    int old_cpu_flag = state.cpu_flag;
+
+    flag |= old_cpu_flag;
+    av_set_cpu_flags_mask(flag);
+    state.cpu_flag = av_get_cpu_flags();
+
+    if (!flag || state.cpu_flag != old_cpu_flag) {
+        int i;
+
+        state.cpu_flag_name = name;
+        for (i = 0; tests[i]; i++)
+            tests[i]();
+    }
+}
+
+/* Print the name of the current CPU flag, but only do it once */
+static void print_cpu_name(void)
+{
+    if (state.cpu_flag_name) {
+        color_printf(COLOR_YELLOW, "%s:\n", state.cpu_flag_name);
+        state.cpu_flag_name = NULL;
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    int i, seed, ret = 0;
+
+    if (!tests[0] || !cpus[0].flag) {
+        fprintf(stderr, "checkasm: no tests to perform\n");
+        return 1;
+    }
+
+    if (argc > 1 && !strncmp(argv[1], "--bench", 7)) {
+#ifndef AV_READ_TIME
+        fprintf(stderr, "checkasm: --bench is not supported on your system\n");
+        return 1;
+#endif
+        if (argv[1][7] == '=') {
+            state.bench_pattern = argv[1] + 8;
+            state.bench_pattern_len = strlen(state.bench_pattern);
+        } else
+            state.bench_pattern = "";
+
+        argc--;
+        argv++;
+    }
+
+    seed = (argc > 1) ? atoi(argv[1]) : av_get_random_seed();
+    fprintf(stderr, "checkasm: using random seed %u\n", seed);
+    av_lfg_init(&checkasm_lfg, seed);
+
+    check_cpu_flag(NULL, 0);
+    for (i = 0; cpus[i].flag; i++)
+        check_cpu_flag(cpus[i].name, cpus[i].flag);
+
+    if (state.num_failed) {
+        fprintf(stderr, "checkasm: %d of %d tests have failed\n", state.num_failed, state.num_checked);
+        ret = 1;
+    } else {
+        fprintf(stderr, "checkasm: all %d tests passed\n", state.num_checked);
+#ifdef AV_READ_TIME
+        if (state.bench_pattern) {
+            state.nop_time = measure_nop_time();
+            printf("nop: %d.%d\n", state.nop_time/10, state.nop_time%10);
+            print_benchs(state.funcs);
+        }
+#endif
+    }
+
+    destroy_func_tree(state.funcs);
+    return ret;
+}
+
+/* Decide whether or not the specified function needs to be tested and
+ * allocate/initialize data structures if needed. Returns a pointer to a
+ * reference function if the function should be tested, otherwise NULL */
+intptr_t (*checkasm_check_func(intptr_t (*func)(), const char *name, ...))()
+{
+    char name_buf[256];
+    intptr_t (*ref)() = func;
+    CheckasmFuncVersion *v;
+    int name_length;
+    va_list arg;
+
+    va_start(arg, name);
+    name_length = vsnprintf(name_buf, sizeof(name_buf), name, arg);
+    va_end(arg);
+
+    if (!func || name_length <= 0 || name_length >= sizeof(name_buf))
+        return NULL;
+
+    state.current_func = get_func(name_buf, name_length);
+    v = &state.current_func->versions;
+
+    if (v->func) {
+        CheckasmFuncVersion *prev;
+        do {
+            /* Only test functions that haven't already been tested */
+            if (v->func == func)
+                return NULL;
+
+            if (v->ok)
+                ref = v->func;
+
+            prev = v;
+        } while ((v = v->next));
+
+        v = prev->next = checkasm_malloc(sizeof(CheckasmFuncVersion));
+    }
+
+    v->func = func;
+    v->ok = 1;
+    v->cpu = state.cpu_flag;
+    state.current_func_ver = v;
+
+    if (state.cpu_flag)
+        state.num_checked++;
+
+    return ref;
+}
+
+/* Decide whether or not the current function needs to be benchmarked */
+int checkasm_bench_func(void)
+{
+    return !state.num_failed && state.bench_pattern &&
+           !strncmp(state.current_func->name, state.bench_pattern, state.bench_pattern_len);
+}
+
+/* Indicate that the current test has failed */
+void checkasm_fail_func(const char *msg, ...)
+{
+    if (state.current_func_ver->cpu && state.current_func_ver->ok) {
+        va_list arg;
+
+        print_cpu_name();
+        fprintf(stderr, "   %s_%s (", state.current_func->name, cpu_suffix(state.current_func_ver->cpu));
+        va_start(arg, msg);
+        vfprintf(stderr, msg, arg);
+        va_end(arg);
+        fprintf(stderr, ")\n");
+
+        state.current_func_ver->ok = 0;
+        state.num_failed++;
+    }
+}
+
+/* Update benchmark results of the current function */
+void checkasm_update_bench(int iterations, uint64_t cycles)
+{
+    state.current_func_ver->iterations += iterations;
+    state.current_func_ver->cycles += cycles;
+}
+
+/* Print the outcome of all tests performed since the last time this function was called */
+void checkasm_report(const char *name, ...)
+{
+    static int prev_checked, prev_failed, max_length;
+
+    if (state.num_checked > prev_checked) {
+        print_cpu_name();
+
+        if (*name) {
+            int pad_length = max_length;
+            va_list arg;
+
+            fprintf(stderr, " - ");
+            va_start(arg, name);
+            pad_length -= vfprintf(stderr, name, arg);
+            va_end(arg);
+            fprintf(stderr, "%*c", FFMAX(pad_length, 0) + 2, '[');
+        } else
+            fprintf(stderr, " - %-*s [", max_length, state.current_func->name);
+
+        if (state.num_failed == prev_failed)
+            color_printf(COLOR_GREEN, "OK");
+        else
+            color_printf(COLOR_RED, "FAILED");
+        fprintf(stderr, "]\n");
+
+        prev_checked = state.num_checked;
+        prev_failed  = state.num_failed;
+    } else if (!state.cpu_flag) {
+        int length;
+
+        /* Calculate the amount of padding required to make the output vertically aligned */
+        if (*name) {
+            va_list arg;
+            va_start(arg, name);
+            length = vsnprintf(NULL, 0, name, arg);
+            va_end(arg);
+        } else
+            length = strlen(state.current_func->name);
+
+        if (length > max_length)
+            max_length = length;
+    }
+}
diff --git a/tests/checkasm/checkasm.h b/tests/checkasm/checkasm.h
new file mode 100644
index 0000000..90844e2
--- /dev/null
+++ b/tests/checkasm/checkasm.h
@@ -0,0 +1,115 @@
+/*
+ * Assembly testing and benchmarking tool
+ * Copyright (c) 2015 Henrik Gramner
+ * Copyright (c) 2008 Loren Merritt
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Libav; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef CHECKASM_H
+#define CHECKASM_H
+
+#include <stdint.h>
+#include "config.h"
+#include "libavutil/avstring.h"
+#include "libavutil/lfg.h"
+#include "libavutil/timer.h"
+
+void checkasm_check_h264pred(void);
+
+intptr_t (*checkasm_check_func(intptr_t (*func)(), const char *name, ...))() av_printf_format(2, 3);
+int checkasm_bench_func(void);
+void checkasm_fail_func(const char *msg, ...) av_printf_format(1, 2);
+void checkasm_update_bench(int iterations, uint64_t cycles);
+void checkasm_report(const char *name, ...) av_printf_format(1, 2);
+
+extern AVLFG checkasm_lfg;
+#define rnd() av_lfg_get(&checkasm_lfg)
+
+static av_unused intptr_t (*func_ref)();
+static av_unused intptr_t (*func_new)();
+
+#define BENCH_RUNS 1000 /* Trade-off between accuracy and speed */
+
+/* Decide whether or not the specified function needs to be tested */
+#define check_func(func, ...) ((func_new = (intptr_t (*)())func) &&\
+                              (func_ref = checkasm_check_func(func_new, __VA_ARGS__)))
+
+/* Indicate that the current test has failed */
+#define fail() checkasm_fail_func("%s:%d", av_basename(__FILE__), __LINE__)
+
+/* Print the test outcome */
+#define report(...) checkasm_report("" __VA_ARGS__)
+
+/* Call the reference function */
+#define call_ref(...) func_ref(__VA_ARGS__)
+
+#if ARCH_X86 && HAVE_YASM
+/* Verifies that clobbered callee-saved registers are properly saved and restored */
+intptr_t checkasm_checked_call(intptr_t (*func)(), ...);
+#endif
+
+/* Call the function */
+#if ARCH_X86_64 && HAVE_YASM
+/* Evil hack: detect incorrect assumptions that 32-bit ints are zero-extended to 64-bit.
+ * This is done by clobbering the stack with junk around the stack pointer and calling the
+ * assembly function through x264_checkasm_call with added dummy arguments which forces all
+ * real arguments to be passed on the stack and not in registers. For 32-bit arguments the
+ * upper half of the 64-bit register locations on the stack will now contain junk which will
+ * cause misbehaving functions to either produce incorrect output or segfault. Note that
+ * even though this works extremely well in practice, it's technically not guaranteed
+ * and false negatives is theoretically possible, but there can never be any false positives.
+ */
+void checkasm_stack_clobber(uint64_t clobber, ...);
+#define CLOB (UINT64_C(0xdeadbeefdeadbeef))
+#define call_new(...) (checkasm_stack_clobber(CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,\
+                                              CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB),\
+                      checkasm_checked_call(func_new, 0, 0, 0, 0, 0, __VA_ARGS__))
+#elif ARCH_X86_32 && HAVE_YASM
+#define call_new(...) checkasm_checked_call(func_new, __VA_ARGS__)
+#else
+#define call_new(...) func_new(__VA_ARGS__)
+#endif
+
+/* Benchmark the function */
+#ifdef AV_READ_TIME
+#define bench_new(...)\
+    do {\
+        if (checkasm_bench_func()) {\
+            intptr_t (*tfunc)() = func_new;\
+            uint64_t tsum = 0;\
+            int ti, tcount = 0;\
+            for (ti = 0; ti < BENCH_RUNS; ti++) {\
+                uint64_t t = AV_READ_TIME();\
+                tfunc(__VA_ARGS__);\
+                tfunc(__VA_ARGS__);\
+                tfunc(__VA_ARGS__);\
+                tfunc(__VA_ARGS__);\
+                t = AV_READ_TIME() - t;\
+                if (t*tcount <= tsum*4 && ti > 0) {\
+                    tsum += t;\
+                    tcount++;\
+                }\
+            }\
+            checkasm_update_bench(tcount, tsum);\
+        }\
+    } while (0)
+#else
+#define bench_new(...)
+#endif
+
+#endif
diff --git a/tests/checkasm/h264pred.c b/tests/checkasm/h264pred.c
new file mode 100644
index 0000000..f0d493d
--- /dev/null
+++ b/tests/checkasm/h264pred.c
@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2015 Henrik Gramner
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Libav; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <string.h>
+#include "checkasm.h"
+#include "libavcodec/avcodec.h"
+#include "libavcodec/h264pred.h"
+#include "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+
+static const int codec_ids[4] = { AV_CODEC_ID_H264, AV_CODEC_ID_VP8, AV_CODEC_ID_RV40, AV_CODEC_ID_SVQ3 };
+
+static const char * const pred4x4_modes[4][15] = {
+    { /* H264 */
+        [VERT_PRED           ] = "vertical",
+        [HOR_PRED            ] = "horizontal",
+        [DC_PRED             ] = "dc",
+        [DIAG_DOWN_LEFT_PRED ] = "down_left",
+        [DIAG_DOWN_RIGHT_PRED] = "down_right",
+        [VERT_RIGHT_PRED     ] = "vertical_right",
+        [HOR_DOWN_PRED       ] = "horizontal_right",
+        [VERT_LEFT_PRED      ] = "vertical_left",
+        [HOR_UP_PRED         ] = "horizontal_up",
+        [LEFT_DC_PRED        ] = "left_dc",
+        [TOP_DC_PRED         ] = "top_dc",
+        [DC_128_PRED         ] = "dc_128",
+    },
+    { /* VP8 */
+        [VERT_PRED     ] = "vertical_vp8",
+        [HOR_PRED      ] = "horizontal_vp8",
+        [VERT_LEFT_PRED] = "vertical_left_vp8",
+        [TM_VP8_PRED   ] = "tm_vp8",
+        [DC_127_PRED   ] = "dc_127_vp8",
+        [DC_129_PRED   ] = "dc_129_vp8",
+    },
+    { /* RV40 */
+        [DIAG_DOWN_LEFT_PRED            ] = "down_left_rv40",
+        [VERT_LEFT_PRED                 ] = "vertical_left_rv40",
+        [HOR_UP_PRED                    ] = "horizontal_up_rv40",
+        [DIAG_DOWN_LEFT_PRED_RV40_NODOWN] = "down_left_nodown_rv40",
+        [HOR_UP_PRED_RV40_NODOWN        ] = "horizontal_up_nodown_rv40",
+        [VERT_LEFT_PRED_RV40_NODOWN     ] = "vertical_left_nodown_rv40",
+    },
+    { /* SVQ3 */
+        [DIAG_DOWN_LEFT_PRED] = "down_left_svq3",
+    },
+};
+
+static const char * const pred8x8_modes[4][11] = {
+    { /* H264 */
+        [DC_PRED8x8              ] = "dc",
+        [HOR_PRED8x8             ] = "horizontal",
+        [VERT_PRED8x8            ] = "vertical",
+        [PLANE_PRED8x8           ] = "plane",
+        [LEFT_DC_PRED8x8         ] = "left_dc",
+        [TOP_DC_PRED8x8          ] = "top_dc",
+        [DC_128_PRED8x8          ] = "dc_128",
+        [ALZHEIMER_DC_L0T_PRED8x8] = "mad_cow_dc_l0t",
+        [ALZHEIMER_DC_0LT_PRED8x8] = "mad_cow_dc_0lt",
+        [ALZHEIMER_DC_L00_PRED8x8] = "mad_cow_dc_l00",
+        [ALZHEIMER_DC_0L0_PRED8x8] = "mad_cow_dc_0l0",
+    },
+    { /* VP8 */
+        [PLANE_PRED8x8 ] = "tm_vp8",
+        [DC_127_PRED8x8] = "dc_127_vp8",
+        [DC_129_PRED8x8] = "dc_129_vp8",
+    },
+    { /* RV40 */
+        [DC_PRED8x8     ] = "dc_rv40",
+        [LEFT_DC_PRED8x8] = "left_dc_rv40",
+        [TOP_DC_PRED8x8 ] = "top_dc_rv40",
+    },
+    { /* SVQ3 */
+    },
+};
+
+static const char * const pred16x16_modes[4][9] = {
+    { /* H264 */
+        [DC_PRED8x8     ] = "dc",
+        [HOR_PRED8x8    ] = "horizontal",
+        [VERT_PRED8x8   ] = "vertical",
+        [PLANE_PRED8x8  ] = "plane",
+        [LEFT_DC_PRED8x8] = "left_dc",
+        [TOP_DC_PRED8x8 ] = "top_dc",
+        [DC_128_PRED8x8 ] = "dc_128",
+    },
+    { /* VP8 */
+        [PLANE_PRED8x8 ] = "tm_vp8",
+        [DC_127_PRED8x8] = "dc_127_vp8",
+        [DC_129_PRED8x8] = "dc_129_vp8",
+    },
+    { /* RV40 */
+        [PLANE_PRED8x8] = "plane_rv40",
+    },
+    { /* SVQ3 */
+        [PLANE_PRED8x8] = "plane_svq3",
+    },
+};
+
+static const uint32_t pixel_mask[3] = { 0xffffffff, 0x01ff01ff, 0x03ff03ff };
+
+#define SIZEOF_PIXEL ((bit_depth + 7) / 8)
+#define BUF_SIZE (3*16*17)
+
+#define check_pred_func(func, name, mode_name)\
+    (mode_name && ((codec_ids[codec] == AV_CODEC_ID_H264) ?\
+    check_func(func, "pred%s_%s_%d", name, mode_name, bit_depth) :\
+    check_func(func, "pred%s_%s", name, mode_name)))
+
+#define randomize_buffers()\
+    do {\
+        uint32_t mask = pixel_mask[bit_depth-8];\
+        int i;\
+        for (i = 0; i < BUF_SIZE; i += 4) {\
+            uint32_t r = rnd() & mask;\
+            AV_WN32A(buf0+i, r);\
+            AV_WN32A(buf1+i, r);\
+        }\
+    } while (0)
+
+#define src0 (buf0 + 4*16) /* Offset to allow room for top and left */
+#define src1 (buf1 + 4*16)
+
+static void check_pred4x4(H264PredContext *h, uint8_t *buf0, uint8_t *buf1,
+                          int codec, int chroma_format, int bit_depth)
+{
+    if (chroma_format == 1) {
+        uint8_t *topright = buf0 + 2*16;
+        int pred_mode;
+        for (pred_mode = 0; pred_mode < 15; pred_mode++) {
+            if (check_pred_func(h->pred4x4[pred_mode], "4x4", pred4x4_modes[codec][pred_mode])) {
+                randomize_buffers();
+                call_ref(src0, topright, (ptrdiff_t)12*SIZEOF_PIXEL);
+                call_new(src1, topright, (ptrdiff_t)12*SIZEOF_PIXEL);
+                if (memcmp(buf0, buf1, BUF_SIZE))
+                    fail();
+                bench_new(src1, topright, (ptrdiff_t)12*SIZEOF_PIXEL);
+            }
+        }
+    }
+}
+
+static void check_pred8x8(H264PredContext *h, uint8_t *buf0, uint8_t *buf1,
+                          int codec, int chroma_format, int bit_depth)
+{
+    int pred_mode;
+    for (pred_mode = 0; pred_mode < 11; pred_mode++) {
+        if (check_pred_func(h->pred8x8[pred_mode], (chroma_format == 2) ? "8x16" : "8x8",
+                            pred8x8_modes[codec][pred_mode])) {
+            randomize_buffers();
+            call_ref(src0, (ptrdiff_t)24*SIZEOF_PIXEL);
+            call_new(src1, (ptrdiff_t)24*SIZEOF_PIXEL);
+            if (memcmp(buf0, buf1, BUF_SIZE))
+                fail();
+            bench_new(src1, (ptrdiff_t)24*SIZEOF_PIXEL);
+        }
+    }
+}
+
+static void check_pred16x16(H264PredContext *h, uint8_t *buf0, uint8_t *buf1,
+                            int codec, int chroma_format, int bit_depth)
+{
+    if (chroma_format == 1) {
+        int pred_mode;
+        for (pred_mode = 0; pred_mode < 9; pred_mode++) {
+            if (check_pred_func(h->pred16x16[pred_mode], "16x16", pred16x16_modes[codec][pred_mode])) {
+                randomize_buffers();
+                call_ref(src0, (ptrdiff_t)48);
+                call_new(src1, (ptrdiff_t)48);
+                if (memcmp(buf0, buf1, BUF_SIZE))
+                    fail();
+                bench_new(src1, (ptrdiff_t)48);
+            }
+        }
+    }
+}
+
+static void check_pred8x8l(H264PredContext *h, uint8_t *buf0, uint8_t *buf1,
+                           int codec, int chroma_format, int bit_depth)
+{
+    if (chroma_format == 1 && codec_ids[codec] == AV_CODEC_ID_H264) {
+        int pred_mode;
+        for (pred_mode = 0; pred_mode < 12; pred_mode++) {
+            if (check_pred_func(h->pred8x8l[pred_mode], "8x8l", pred4x4_modes[codec][pred_mode])) {
+                int neighbors;
+                for (neighbors = 0; neighbors <= 0xc000; neighbors += 0x4000) {
+                    int has_topleft  = neighbors & 0x8000;
+                    int has_topright = neighbors & 0x4000;
+
+                    if ((pred_mode == DIAG_DOWN_RIGHT_PRED || pred_mode == VERT_RIGHT_PRED) && !has_topleft)
+                        continue; /* Those aren't allowed according to the spec */
+
+                    randomize_buffers();
+                    call_ref(src0, has_topleft, has_topright, (ptrdiff_t)24*SIZEOF_PIXEL);
+                    call_new(src1, has_topleft, has_topright, (ptrdiff_t)24*SIZEOF_PIXEL);
+                    if (memcmp(buf0, buf1, BUF_SIZE))
+                        fail();
+                    bench_new(src1, has_topleft, has_topright, (ptrdiff_t)24*SIZEOF_PIXEL);
+                }
+            }
+        }
+    }
+}
+
+/* TODO: Add tests for H.264 lossless H/V prediction */
+
+void checkasm_check_h264pred(void)
+{
+    static const struct {
+        void (*func)(H264PredContext*, uint8_t*, uint8_t*, int, int, int);
+        const char *name;
+    } tests[] = {
+        { check_pred4x4,   "pred4x4"   },
+        { check_pred8x8,   "pred8x8"   },
+        { check_pred16x16, "pred16x16" },
+        { check_pred8x8l,  "pred8x8l"  },
+    };
+
+    DECLARE_ALIGNED(16, uint8_t, buf0)[BUF_SIZE];
+    DECLARE_ALIGNED(16, uint8_t, buf1)[BUF_SIZE];
+    H264PredContext h;
+    int test, codec, chroma_format, bit_depth;
+
+    for (test = 0; test < FF_ARRAY_ELEMS(tests); test++) {
+        for (codec = 0; codec < 4; codec++) {
+            int codec_id = codec_ids[codec];
+            for (bit_depth = 8; bit_depth <= (codec_id == AV_CODEC_ID_H264 ? 10 : 8); bit_depth++)
+                for (chroma_format = 1; chroma_format <= (codec_id == AV_CODEC_ID_H264 ? 2 : 1); chroma_format++) {
+                    ff_h264_pred_init(&h, codec_id, bit_depth, chroma_format);
+                    tests[test].func(&h, buf0, buf1, codec, chroma_format, bit_depth);
+                }
+        }
+        report("%s", tests[test].name);
+    }
+}
diff --git a/tests/checkasm/x86/Makefile b/tests/checkasm/x86/Makefile
new file mode 100644
index 0000000..0254c61
--- /dev/null
+++ b/tests/checkasm/x86/Makefile
@@ -0,0 +1,6 @@
+CHECKASMOBJS-$(HAVE_YASM) += x86/checkasm.o
+
+tests/checkasm/x86/%.o: tests/checkasm/x86/%.asm
+	$(DEPYASM) $(YASMFLAGS) -I $(<D)/ -M -o $@ $< > $(@:.o=.d)
+	$(YASM) $(YASMFLAGS) -I $(<D)/ -o $@ $<
+	-$(STRIP) $(STRIPFLAGS) $@
diff --git a/tests/checkasm/x86/checkasm.asm b/tests/checkasm/x86/checkasm.asm
new file mode 100644
index 0000000..0864a4f
--- /dev/null
+++ b/tests/checkasm/x86/checkasm.asm
@@ -0,0 +1,193 @@
+;*****************************************************************************
+;* Assembly testing and benchmarking tool
+;* Copyright (c) 2008 Loren Merritt
+;* Copyright (c) 2012 Henrik Gramner
+;*
+;* This file is part of Libav.
+;*
+;* Libav is free software; you can redistribute it and/or modify
+;* it under the terms of the GNU General Public License as published by
+;* the Free Software Foundation; either version 2 of the License, or
+;* (at your option) any later version.
+;*
+;* Libav is distributed in the hope that it will be useful,
+;* but WITHOUT ANY WARRANTY; without even the implied warranty of
+;* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;* GNU General Public License for more details.
+;*
+;* You should have received a copy of the GNU General Public License
+;* along with this program; if not, write to the Free Software
+;* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02111, USA.
+;*****************************************************************************
+
+%define private_prefix checkasm
+%include "libavutil/x86/x86inc.asm"
+
+SECTION_RODATA
+
+error_message: db "failed to preserve register", 0
+
+%if ARCH_X86_64
+; just random numbers to reduce the chance of incidental match
+ALIGN 16
+x6:  dq 0x1a1b2550a612b48c,0x79445c159ce79064
+x7:  dq 0x2eed899d5a28ddcd,0x86b2536fcd8cf636
+x8:  dq 0xb0856806085e7943,0x3f2bf84fc0fcca4e
+x9:  dq 0xacbd382dcf5b8de2,0xd229e1f5b281303f
+x10: dq 0x71aeaff20b095fd9,0xab63e2e11fa38ed9
+x11: dq 0x89b0c0765892729a,0x77d410d5c42c882d
+x12: dq 0xc45ea11a955d8dd5,0x24b3c1d2a024048b
+x13: dq 0x2e8ec680de14b47c,0xdd7b8919edd42786
+x14: dq 0x135ce6888fa02cbf,0x11e53e2b2ac655ef
+x15: dq 0x011ff554472a7a10,0x6de8f4c914c334d5
+n7:  dq 0x21f86d66c8ca00ce
+n8:  dq 0x75b6ba21077c48ad
+n9:  dq 0xed56bb2dcb3c7736
+n10: dq 0x8bda43d3fd1a7e06
+n11: dq 0xb64a9c9e5d318408
+n12: dq 0xdf9a54b303f1d3a3
+n13: dq 0x4a75479abd64e097
+n14: dq 0x249214109d5d1c88
+%endif
+
+SECTION .text
+
+cextern fail_func
+
+; max number of args used by any asm function.
+; (max_args % 4) must equal 3 for stack alignment
+%define max_args 15
+
+%if ARCH_X86_64
+
+;-----------------------------------------------------------------------------
+; int checkasm_stack_clobber(uint64_t clobber, ...)
+;-----------------------------------------------------------------------------
+cglobal stack_clobber, 1,2
+    ; Clobber the stack with junk below the stack pointer
+    %define size (max_args+6)*8
+    SUB  rsp, size
+    mov   r1, size-8
+.loop:
+    mov [rsp+r1], r0
+    sub   r1, 8
+    jge .loop
+    ADD  rsp, size
+    RET
+
+%if WIN64
+    %assign free_regs 7
+%else
+    %assign free_regs 9
+%endif
+
+;-----------------------------------------------------------------------------
+; intptr_t checkasm_checked_call(intptr_t (*func)(), ...)
+;-----------------------------------------------------------------------------
+INIT_XMM
+cglobal checked_call, 2,15,16,max_args*8+8
+    mov  r6, r0
+
+    ; All arguments have been pushed on the stack instead of registers in order to
+    ; test for incorrect assumptions that 32-bit ints are zero-extended to 64-bit.
+    mov  r0, r6mp
+    mov  r1, r7mp
+    mov  r2, r8mp
+    mov  r3, r9mp
+%if UNIX64
+    mov  r4, r10mp
+    mov  r5, r11mp
+    %assign i 6
+    %rep max_args-6
+        mov  r9, [rsp+stack_offset+(i+1)*8]
+        mov  [rsp+(i-6)*8], r9
+        %assign i i+1
+    %endrep
+%else
+    %assign i 4
+    %rep max_args-4
+        mov  r9, [rsp+stack_offset+(i+7)*8]
+        mov  [rsp+i*8], r9
+        %assign i i+1
+    %endrep
+%endif
+
+%if WIN64
+    %assign i 6
+    %rep 16-6
+        mova m %+ i, [x %+ i]
+        %assign i i+1
+    %endrep
+%endif
+
+%assign i 14
+%rep 15-free_regs
+    mov r %+ i, [n %+ i]
+    %assign i i-1
+%endrep
+    call r6
+%assign i 14
+%rep 15-free_regs
+    xor r %+ i, [n %+ i]
+    or  r14, r %+ i
+    %assign i i-1
+%endrep
+
+%if WIN64
+    %assign i 6
+    %rep 16-6
+        pxor m %+ i, [x %+ i]
+        por  m6, m %+ i
+        %assign i i+1
+    %endrep
+    packsswb m6, m6
+    movq r5, m6
+    or  r14, r5
+%endif
+
+    jz .ok
+    mov  r9, rax
+    lea  r0, [error_message]
+    call fail_func
+    mov rax, r9
+.ok:
+    RET
+
+%else
+
+; just random numbers to reduce the chance of incidental match
+%define n3 dword 0x6549315c
+%define n4 dword 0xe02f3e23
+%define n5 dword 0xb78d0d1d
+%define n6 dword 0x33627ba7
+
+;-----------------------------------------------------------------------------
+; intptr_t checkasm_checked_call(intptr_t (*func)(), ...)
+;-----------------------------------------------------------------------------
+cglobal checked_call, 1,7
+    mov  r3, n3
+    mov  r4, n4
+    mov  r5, n5
+    mov  r6, n6
+%rep max_args
+    PUSH dword [esp+20+max_args*4]
+%endrep
+    call r0
+    xor  r3, n3
+    xor  r4, n4
+    xor  r5, n5
+    xor  r6, n6
+    or   r3, r4
+    or   r5, r6
+    or   r3, r5
+    jz .ok
+    mov  r3, eax
+    lea  r0, [error_message]
+    mov [esp], r0
+    call fail_func
+    mov  eax, r3
+.ok:
+    add  esp, max_args*4
+    REP_RET
+
+%endif ; ARCH_X86_64