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skia2/platform_tools/android/third_party/cpufeatures/cpu-features.c
djsollen@google.com dcdd57faf0 Copy the top level Android directory into trunk. 
This CL is the first step in a series needed to move the
android directory into trunk. After the copy we will update
GYP and DEPS to point to the new location and only then
remove the original directory.

git-svn-id: http://skia.googlecode.com/svn/trunk@8891 2bbb7eff-a529-9590-31e7-b0007b416f81
2013-04-29 12:09:31 +00:00

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/*
* Copyright (C) 2010 The Android Open Source Project
* 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.
*/
/* ChangeLog for this library:
*
* NDK r8d: Add android_setCpu().
*
* NDK r8c: Add new ARM CPU features: VFPv2, VFP_D32, VFP_FP16,
* VFP_FMA, NEON_FMA, IDIV_ARM, IDIV_THUMB2 and iWMMXt.
*
* Rewrite the code to parse /proc/self/auxv instead of
* the "Features" field in /proc/cpuinfo.
*
* Dynamically allocate the buffer that hold the content
* of /proc/cpuinfo to deal with newer hardware.
*
* NDK r7c: Fix CPU count computation. The old method only reported the
* number of _active_ CPUs when the library was initialized,
* which could be less than the real total.
*
* NDK r5: Handle buggy kernels which report a CPU Architecture number of 7
* for an ARMv6 CPU (see below).
*
* Handle kernels that only report 'neon', and not 'vfpv3'
* (VFPv3 is mandated by the ARM architecture is Neon is implemented)
*
* Handle kernels that only report 'vfpv3d16', and not 'vfpv3'
*
* Fix x86 compilation. Report ANDROID_CPU_FAMILY_X86 in
* android_getCpuFamily().
*
* NDK r4: Initial release
*/
#include <sys/system_properties.h>
#ifdef __arm__
#include <machine/cpu-features.h>
#endif
#include <pthread.h>
#include "cpu-features.h"
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
static pthread_once_t g_once;
static int g_inited;
static AndroidCpuFamily g_cpuFamily;
static uint64_t g_cpuFeatures;
static int g_cpuCount;
static const int android_cpufeatures_debug = 0;
#ifdef __arm__
# define DEFAULT_CPU_FAMILY ANDROID_CPU_FAMILY_ARM
#elif defined __i386__
# define DEFAULT_CPU_FAMILY ANDROID_CPU_FAMILY_X86
#else
# define DEFAULT_CPU_FAMILY ANDROID_CPU_FAMILY_UNKNOWN
#endif
#define D(...) \
do { \
if (android_cpufeatures_debug) { \
printf(__VA_ARGS__); fflush(stdout); \
} \
} while (0)
#ifdef __i386__
static __inline__ void x86_cpuid(int func, int values[4])
{
int a, b, c, d;
/* We need to preserve ebx since we're compiling PIC code */
/* this means we can't use "=b" for the second output register */
__asm__ __volatile__ ( \
"push %%ebx\n"
"cpuid\n" \
"mov %%ebx, %1\n"
"pop %%ebx\n"
: "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
: "a" (func) \
);
values[0] = a;
values[1] = b;
values[2] = c;
values[3] = d;
}
#endif
/* Get the size of a file by reading it until the end. This is needed
* because files under /proc do not always return a valid size when
* using fseek(0, SEEK_END) + ftell(). Nor can they be mmap()-ed.
*/
static int
get_file_size(const char* pathname)
{
int fd, ret, result = 0;
char buffer[256];
fd = open(pathname, O_RDONLY);
if (fd < 0) {
D("Can't open %s: %s\n", pathname, strerror(errno));
return -1;
}
for (;;) {
int ret = read(fd, buffer, sizeof buffer);
if (ret < 0) {
if (errno == EINTR)
continue;
D("Error while reading %s: %s\n", pathname, strerror(errno));
break;
}
if (ret == 0)
break;
result += ret;
}
close(fd);
return result;
}
/* Read the content of /proc/cpuinfo into a user-provided buffer.
* Return the length of the data, or -1 on error. Does *not*
* zero-terminate the content. Will not read more
* than 'buffsize' bytes.
*/
static int
read_file(const char* pathname, char* buffer, size_t buffsize)
{
int fd, count;
fd = open(pathname, O_RDONLY);
if (fd < 0) {
D("Could not open %s: %s\n", pathname, strerror(errno));
return -1;
}
count = 0;
while (count < (int)buffsize) {
int ret = read(fd, buffer + count, buffsize - count);
if (ret < 0) {
if (errno == EINTR)
continue;
D("Error while reading from %s: %s\n", pathname, strerror(errno));
if (count == 0)
count = -1;
break;
}
if (ret == 0)
break;
count += ret;
}
close(fd);
return count;
}
/* Extract the content of a the first occurence of a given field in
* the content of /proc/cpuinfo and return it as a heap-allocated
* string that must be freed by the caller.
*
* Return NULL if not found
*/
static char*
extract_cpuinfo_field(char* buffer, int buflen, const char* field)
{
int fieldlen = strlen(field);
char* bufend = buffer + buflen;
char* result = NULL;
int len, ignore;
const char *p, *q;
/* Look for first field occurence, and ensures it starts the line. */
p = buffer;
bufend = buffer + buflen;
for (;;) {
p = memmem(p, bufend-p, field, fieldlen);
if (p == NULL)
goto EXIT;
if (p == buffer || p[-1] == '\n')
break;
p += fieldlen;
}
/* Skip to the first column followed by a space */
p += fieldlen;
p = memchr(p, ':', bufend-p);
if (p == NULL || p[1] != ' ')
goto EXIT;
/* Find the end of the line */
p += 2;
q = memchr(p, '\n', bufend-p);
if (q == NULL)
q = bufend;
/* Copy the line into a heap-allocated buffer */
len = q-p;
result = malloc(len+1);
if (result == NULL)
goto EXIT;
memcpy(result, p, len);
result[len] = '\0';
EXIT:
return result;
}
/* Like strlen(), but for constant string literals */
#define STRLEN_CONST(x) ((sizeof(x)-1)
/* Checks that a space-separated list of items contains one given 'item'.
* Returns 1 if found, 0 otherwise.
*/
static int
has_list_item(const char* list, const char* item)
{
const char* p = list;
int itemlen = strlen(item);
if (list == NULL)
return 0;
while (*p) {
const char* q;
/* skip spaces */
while (*p == ' ' || *p == '\t')
p++;
/* find end of current list item */
q = p;
while (*q && *q != ' ' && *q != '\t')
q++;
if (itemlen == q-p && !memcmp(p, item, itemlen))
return 1;
/* skip to next item */
p = q;
}
return 0;
}
/* Parse an decimal integer starting from 'input', but not going further
* than 'limit'. Return the value into '*result'.
*
* NOTE: Does not skip over leading spaces, or deal with sign characters.
* NOTE: Ignores overflows.
*
* The function returns NULL in case of error (bad format), or the new
* position after the decimal number in case of success (which will always
* be <= 'limit').
*/
static const char*
parse_decimal(const char* input, const char* limit, int* result)
{
const char* p = input;
int val = 0;
while (p < limit) {
int d = (*p - '0');
if ((unsigned)d >= 10U)
break;
val = val*10 + d;
p++;
}
if (p == input)
return NULL;
*result = val;
return p;
}
/* This small data type is used to represent a CPU list / mask, as read
* from sysfs on Linux. See http://www.kernel.org/doc/Documentation/cputopology.txt
*
* For now, we don't expect more than 32 cores on mobile devices, so keep
* everything simple.
*/
typedef struct {
uint32_t mask;
} CpuList;
static __inline__ void
cpulist_init(CpuList* list) {
list->mask = 0;
}
static __inline__ void
cpulist_and(CpuList* list1, CpuList* list2) {
list1->mask &= list2->mask;
}
static __inline__ void
cpulist_set(CpuList* list, int index) {
if ((unsigned)index < 32) {
list->mask |= (uint32_t)(1U << index);
}
}
static __inline__ int
cpulist_count(CpuList* list) {
return __builtin_popcount(list->mask);
}
/* Parse a textual list of cpus and store the result inside a CpuList object.
* Input format is the following:
* - comma-separated list of items (no spaces)
* - each item is either a single decimal number (cpu index), or a range made
* of two numbers separated by a single dash (-). Ranges are inclusive.
*
* Examples: 0
* 2,4-127,128-143
* 0-1
*/
static void
cpulist_parse(CpuList* list, const char* line, int line_len)
{
const char* p = line;
const char* end = p + line_len;
const char* q;
/* NOTE: the input line coming from sysfs typically contains a
* trailing newline, so take care of it in the code below
*/
while (p < end && *p != '\n')
{
int val, start_value, end_value;
/* Find the end of current item, and put it into 'q' */
q = memchr(p, ',', end-p);
if (q == NULL) {
q = end;
}
/* Get first value */
p = parse_decimal(p, q, &start_value);
if (p == NULL)
goto BAD_FORMAT;
end_value = start_value;
/* If we're not at the end of the item, expect a dash and
* and integer; extract end value.
*/
if (p < q && *p == '-') {
p = parse_decimal(p+1, q, &end_value);
if (p == NULL)
goto BAD_FORMAT;
}
/* Set bits CPU list bits */
for (val = start_value; val <= end_value; val++) {
cpulist_set(list, val);
}
/* Jump to next item */
p = q;
if (p < end)
p++;
}
BAD_FORMAT:
;
}
/* Read a CPU list from one sysfs file */
static void
cpulist_read_from(CpuList* list, const char* filename)
{
char file[64];
int filelen;
cpulist_init(list);
filelen = read_file(filename, file, sizeof file);
if (filelen < 0) {
D("Could not read %s: %s\n", filename, strerror(errno));
return;
}
cpulist_parse(list, file, filelen);
}
// See <asm/hwcap.h> kernel header.
#define HWCAP_VFP (1 << 6)
#define HWCAP_IWMMXT (1 << 9)
#define HWCAP_NEON (1 << 12)
#define HWCAP_VFPv3 (1 << 13)
#define HWCAP_VFPv3D16 (1 << 14)
#define HWCAP_VFPv4 (1 << 16)
#define HWCAP_IDIVA (1 << 17)
#define HWCAP_IDIVT (1 << 18)
#define AT_HWCAP 16
/* Read the ELF HWCAP flags by parsing /proc/self/auxv
*/
static uint32_t
get_elf_hwcap(void)
{
uint32_t result = 0;
const char filepath[] = "/proc/self/auxv";
int fd = open(filepath, O_RDONLY);
if (fd < 0) {
D("Could not open %s: %s\n", filepath, strerror(errno));
return 0;
}
struct { uint32_t tag; uint32_t value; } entry;
for (;;) {
int ret = read(fd, (char*)&entry, sizeof entry);
if (ret < 0) {
if (errno == EINTR)
continue;
D("Error while reading %s: %s\n", filepath, strerror(errno));
break;
}
// Detect end of list.
if (ret == 0 || (entry.tag == 0 && entry.value == 0))
break;
if (entry.tag == AT_HWCAP) {
result = entry.value;
break;
}
}
close(fd);
return result;
}
/* Return the number of cpus present on a given device.
*
* To handle all weird kernel configurations, we need to compute the
* intersection of the 'present' and 'possible' CPU lists and count
* the result.
*/
static int
get_cpu_count(void)
{
CpuList cpus_present[1];
CpuList cpus_possible[1];
cpulist_read_from(cpus_present, "/sys/devices/system/cpu/present");
cpulist_read_from(cpus_possible, "/sys/devices/system/cpu/possible");
/* Compute the intersection of both sets to get the actual number of
* CPU cores that can be used on this device by the kernel.
*/
cpulist_and(cpus_present, cpus_possible);
return cpulist_count(cpus_present);
}
static void
android_cpuInitFamily(void)
{
#if defined(__ARM_ARCH__)
g_cpuFamily = ANDROID_CPU_FAMILY_ARM;
#elif defined(__i386__)
g_cpuFamily = ANDROID_CPU_FAMILY_X86;
#elif defined(_MIPS_ARCH)
g_cpuFamily = ANDROID_CPU_FAMILY_MIPS;
#else
g_cpuFamily = ANDROID_CPU_FAMILY_UNKNOWN;
#endif
}
static void
android_cpuInit(void)
{
char* cpuinfo = NULL;
int cpuinfo_len;
android_cpuInitFamily();
g_cpuFeatures = 0;
g_cpuCount = 1;
g_inited = 1;
cpuinfo_len = get_file_size("/proc/cpuinfo");
if (cpuinfo_len < 0) {
D("cpuinfo_len cannot be computed!");
return;
}
cpuinfo = malloc(cpuinfo_len);
if (cpuinfo == NULL) {
D("cpuinfo buffer could not be allocated");
return;
}
cpuinfo_len = read_file("/proc/cpuinfo", cpuinfo, cpuinfo_len);
D("cpuinfo_len is (%d):\n%.*s\n", cpuinfo_len,
cpuinfo_len >= 0 ? cpuinfo_len : 0, cpuinfo);
if (cpuinfo_len < 0) /* should not happen */ {
free(cpuinfo);
return;
}
/* Count the CPU cores, the value may be 0 for single-core CPUs */
g_cpuCount = get_cpu_count();
if (g_cpuCount == 0) {
g_cpuCount = 1;
}
D("found cpuCount = %d\n", g_cpuCount);
#ifdef __ARM_ARCH__
{
char* features = NULL;
char* architecture = NULL;
/* Extract architecture from the "CPU Architecture" field.
* The list is well-known, unlike the the output of
* the 'Processor' field which can vary greatly.
*
* See the definition of the 'proc_arch' array in
* $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
* same file.
*/
char* cpuArch = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "CPU architecture");
if (cpuArch != NULL) {
char* end;
long archNumber;
int hasARMv7 = 0;
D("found cpuArch = '%s'\n", cpuArch);
/* read the initial decimal number, ignore the rest */
archNumber = strtol(cpuArch, &end, 10);
/* Here we assume that ARMv8 will be upwards compatible with v7
* in the future. Unfortunately, there is no 'Features' field to
* indicate that Thumb-2 is supported.
*/
if (end > cpuArch && archNumber >= 7) {
hasARMv7 = 1;
}
/* Unfortunately, it seems that certain ARMv6-based CPUs
* report an incorrect architecture number of 7!
*
* See http://code.google.com/p/android/issues/detail?id=10812
*
* We try to correct this by looking at the 'elf_format'
* field reported by the 'Processor' field, which is of the
* form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
* an ARMv6-one.
*/
if (hasARMv7) {
char* cpuProc = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
"Processor");
if (cpuProc != NULL) {
D("found cpuProc = '%s'\n", cpuProc);
if (has_list_item(cpuProc, "(v6l)")) {
D("CPU processor and architecture mismatch!!\n");
hasARMv7 = 0;
}
free(cpuProc);
}
}
if (hasARMv7) {
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_ARMv7;
}
/* The LDREX / STREX instructions are available from ARMv6 */
if (archNumber >= 6) {
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_LDREX_STREX;
}
free(cpuArch);
}
/* Extract the list of CPU features from ELF hwcaps */
uint32_t hwcaps = get_elf_hwcap();
if (hwcaps != 0) {
int has_vfp = (hwcaps & HWCAP_VFP);
int has_vfpv3 = (hwcaps & HWCAP_VFPv3);
int has_vfpv3d16 = (hwcaps & HWCAP_VFPv3D16);
int has_vfpv4 = (hwcaps & HWCAP_VFPv4);
int has_neon = (hwcaps & HWCAP_NEON);
int has_idiva = (hwcaps & HWCAP_IDIVA);
int has_idivt = (hwcaps & HWCAP_IDIVT);
int has_iwmmxt = (hwcaps & HWCAP_IWMMXT);
// The kernel does a poor job at ensuring consistency when
// describing CPU features. So lots of guessing is needed.
// 'vfpv4' implies VFPv3|VFP_FMA|FP16
if (has_vfpv4)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3 |
ANDROID_CPU_ARM_FEATURE_VFP_FP16 |
ANDROID_CPU_ARM_FEATURE_VFP_FMA;
// 'vfpv3' or 'vfpv3d16' imply VFPv3. Note that unlike GCC,
// a value of 'vfpv3' doesn't necessarily mean that the D32
// feature is present, so be conservative. All CPUs in the
// field that support D32 also support NEON, so this should
// not be a problem in practice.
if (has_vfpv3 || has_vfpv3d16)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3;
// 'vfp' is super ambiguous. Depending on the kernel, it can
// either mean VFPv2 or VFPv3. Make it depend on ARMv7.
if (has_vfp) {
if (g_cpuFeatures & ANDROID_CPU_ARM_FEATURE_ARMv7)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3;
else
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv2;
}
// Neon implies VFPv3|D32, and if vfpv4 is detected, NEON_FMA
if (has_neon) {
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3 |
ANDROID_CPU_ARM_FEATURE_NEON |
ANDROID_CPU_ARM_FEATURE_VFP_D32;
if (has_vfpv4)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_NEON_FMA;
}
// VFPv3 implies VFPv2 and ARMv7
if (g_cpuFeatures & ANDROID_CPU_ARM_FEATURE_VFPv3)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv2 |
ANDROID_CPU_ARM_FEATURE_ARMv7;
// Note that some buggy kernels do not report these even when
// the CPU actually support the division instructions. However,
// assume that if 'vfpv4' is detected, then the CPU supports
// sdiv/udiv properly.
if (has_idiva || has_vfpv4)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_IDIV_ARM;
if (has_idivt || has_vfpv4)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2;
if (has_iwmmxt)
g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_iWMMXt;
}
}
#endif /* __ARM_ARCH__ */
#ifdef __i386__
int regs[4];
/* According to http://en.wikipedia.org/wiki/CPUID */
#define VENDOR_INTEL_b 0x756e6547
#define VENDOR_INTEL_c 0x6c65746e
#define VENDOR_INTEL_d 0x49656e69
x86_cpuid(0, regs);
int vendorIsIntel = (regs[1] == VENDOR_INTEL_b &&
regs[2] == VENDOR_INTEL_c &&
regs[3] == VENDOR_INTEL_d);
x86_cpuid(1, regs);
if ((regs[2] & (1 << 9)) != 0) {
g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_SSSE3;
}
if ((regs[2] & (1 << 23)) != 0) {
g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_POPCNT;
}
if (vendorIsIntel && (regs[2] & (1 << 22)) != 0) {
g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_MOVBE;
}
#endif
free(cpuinfo);
}
AndroidCpuFamily
android_getCpuFamily(void)
{
pthread_once(&g_once, android_cpuInit);
return g_cpuFamily;
}
uint64_t
android_getCpuFeatures(void)
{
pthread_once(&g_once, android_cpuInit);
return g_cpuFeatures;
}
int
android_getCpuCount(void)
{
pthread_once(&g_once, android_cpuInit);
return g_cpuCount;
}
static void
android_cpuInitDummy(void)
{
g_inited = 1;
}
int
android_setCpu(int cpu_count, uint64_t cpu_features)
{
/* Fail if the library was already initialized. */
if (g_inited)
return 0;
android_cpuInitFamily();
g_cpuCount = (cpu_count <= 0 ? 1 : cpu_count);
g_cpuFeatures = cpu_features;
pthread_once(&g_once, android_cpuInitDummy);
return 1;
}
/*
* Technical note: Making sense of ARM's FPU architecture versions.
*
* FPA was ARM's first attempt at an FPU architecture. There is no Android
* device that actually uses it since this technology was already obsolete
* when the project started. If you see references to FPA instructions
* somewhere, you can be sure that this doesn't apply to Android at all.
*
* FPA was followed by "VFP", soon renamed "VFPv1" due to the emergence of
* new versions / additions to it. ARM considers this obsolete right now,
* and no known Android device implements it either.
*
* VFPv2 added a few instructions to VFPv1, and is an *optional* extension
* supported by some ARMv5TE, ARMv6 and ARMv6T2 CPUs. Note that a device
* supporting the 'armeabi' ABI doesn't necessarily support these.
*
* VFPv3-D16 adds a few instructions on top of VFPv2 and is typically used
* on ARMv7-A CPUs which implement a FPU. Note that it is also mandated
* by the Android 'armeabi-v7a' ABI. The -D16 suffix in its name means
* that it provides 16 double-precision FPU registers (d0-d15) and 32
* single-precision ones (s0-s31) which happen to be mapped to the same
* register banks.
*
* VFPv3-D32 is the name of an extension to VFPv3-D16 that provides 16
* additional double precision registers (d16-d31). Note that there are
* still only 32 single precision registers.
*
* VFPv3xD is a *subset* of VFPv3-D16 that only provides single-precision
* registers. It is only used on ARMv7-M (i.e. on micro-controllers) which
* are not supported by Android. Note that it is not compatible with VFPv2.
*
* NOTE: The term 'VFPv3' usually designate either VFPv3-D16 or VFPv3-D32
* depending on context. For example GCC uses it for VFPv3-D32, but
* the Linux kernel code uses it for VFPv3-D16 (especially in
* /proc/cpuinfo). Always try to use the full designation when
* possible.
*
* NEON, a.k.a. "ARM Advanced SIMD" is an extension that provides
* instructions to perform parallel computations on vectors of 8, 16,
* 32, 64 and 128 bit quantities. NEON requires VFPv32-D32 since all
* NEON registers are also mapped to the same register banks.
*
* VFPv4-D16, adds a few instructions on top of VFPv3-D16 in order to
* perform fused multiply-accumulate on VFP registers, as well as
* half-precision (16-bit) conversion operations.
*
* VFPv4-D32 is VFPv4-D16 with 32, instead of 16, FPU double precision
* registers.
*
* VPFv4-NEON is VFPv4-D32 with NEON instructions. It also adds fused
* multiply-accumulate instructions that work on the NEON registers.
*
* NOTE: Similarly, "VFPv4" might either reference VFPv4-D16 or VFPv4-D32
* depending on context.
*
* The following information was determined by scanning the binutils-2.22
* sources:
*
* Basic VFP instruction subsets:
*
* #define FPU_VFP_EXT_V1xD 0x08000000 // Base VFP instruction set.
* #define FPU_VFP_EXT_V1 0x04000000 // Double-precision insns.
* #define FPU_VFP_EXT_V2 0x02000000 // ARM10E VFPr1.
* #define FPU_VFP_EXT_V3xD 0x01000000 // VFPv3 single-precision.
* #define FPU_VFP_EXT_V3 0x00800000 // VFPv3 double-precision.
* #define FPU_NEON_EXT_V1 0x00400000 // Neon (SIMD) insns.
* #define FPU_VFP_EXT_D32 0x00200000 // Registers D16-D31.
* #define FPU_VFP_EXT_FP16 0x00100000 // Half-precision extensions.
* #define FPU_NEON_EXT_FMA 0x00080000 // Neon fused multiply-add
* #define FPU_VFP_EXT_FMA 0x00040000 // VFP fused multiply-add
*
* FPU types (excluding NEON)
*
* FPU_VFP_V1xD (EXT_V1xD)
* |
* +--------------------------+
* | |
* FPU_VFP_V1 (+EXT_V1) FPU_VFP_V3xD (+EXT_V2+EXT_V3xD)
* | |
* | |
* FPU_VFP_V2 (+EXT_V2) FPU_VFP_V4_SP_D16 (+EXT_FP16+EXT_FMA)
* |
* FPU_VFP_V3D16 (+EXT_Vx3D+EXT_V3)
* |
* +--------------------------+
* | |
* FPU_VFP_V3 (+EXT_D32) FPU_VFP_V4D16 (+EXT_FP16+EXT_FMA)
* | |
* | FPU_VFP_V4 (+EXT_D32)
* |
* FPU_VFP_HARD (+EXT_FMA+NEON_EXT_FMA)
*
* VFP architectures:
*
* ARCH_VFP_V1xD (EXT_V1xD)
* |
* +------------------+
* | |
* | ARCH_VFP_V3xD (+EXT_V2+EXT_V3xD)
* | |
* | ARCH_VFP_V3xD_FP16 (+EXT_FP16)
* | |
* | ARCH_VFP_V4_SP_D16 (+EXT_FMA)
* |
* ARCH_VFP_V1 (+EXT_V1)
* |
* ARCH_VFP_V2 (+EXT_V2)
* |
* ARCH_VFP_V3D16 (+EXT_V3xD+EXT_V3)
* |
* +-------------------+
* | |
* | ARCH_VFP_V3D16_FP16 (+EXT_FP16)
* |
* +-------------------+
* | |
* | ARCH_VFP_V4_D16 (+EXT_FP16+EXT_FMA)
* | |
* | ARCH_VFP_V4 (+EXT_D32)
* | |
* | ARCH_NEON_VFP_V4 (+EXT_NEON+EXT_NEON_FMA)
* |
* ARCH_VFP_V3 (+EXT_D32)
* |
* +-------------------+
* | |
* | ARCH_VFP_V3_FP16 (+EXT_FP16)
* |
* ARCH_VFP_V3_PLUS_NEON_V1 (+EXT_NEON)
* |
* ARCH_NEON_FP16 (+EXT_FP16)
*
* -fpu=<name> values and their correspondance with FPU architectures above:
*
* {"vfp", FPU_ARCH_VFP_V2},
* {"vfp9", FPU_ARCH_VFP_V2},
* {"vfp3", FPU_ARCH_VFP_V3}, // For backwards compatbility.
* {"vfp10", FPU_ARCH_VFP_V2},
* {"vfp10-r0", FPU_ARCH_VFP_V1},
* {"vfpxd", FPU_ARCH_VFP_V1xD},
* {"vfpv2", FPU_ARCH_VFP_V2},
* {"vfpv3", FPU_ARCH_VFP_V3},
* {"vfpv3-fp16", FPU_ARCH_VFP_V3_FP16},
* {"vfpv3-d16", FPU_ARCH_VFP_V3D16},
* {"vfpv3-d16-fp16", FPU_ARCH_VFP_V3D16_FP16},
* {"vfpv3xd", FPU_ARCH_VFP_V3xD},
* {"vfpv3xd-fp16", FPU_ARCH_VFP_V3xD_FP16},
* {"neon", FPU_ARCH_VFP_V3_PLUS_NEON_V1},
* {"neon-fp16", FPU_ARCH_NEON_FP16},
* {"vfpv4", FPU_ARCH_VFP_V4},
* {"vfpv4-d16", FPU_ARCH_VFP_V4D16},
* {"fpv4-sp-d16", FPU_ARCH_VFP_V4_SP_D16},
* {"neon-vfpv4", FPU_ARCH_NEON_VFP_V4},
*
*
* Simplified diagram that only includes FPUs supported by Android:
* Only ARCH_VFP_V3D16 is actually mandated by the armeabi-v7a ABI,
* all others are optional and must be probed at runtime.
*
* ARCH_VFP_V3D16 (EXT_V1xD+EXT_V1+EXT_V2+EXT_V3xD+EXT_V3)
* |
* +-------------------+
* | |
* | ARCH_VFP_V3D16_FP16 (+EXT_FP16)
* |
* +-------------------+
* | |
* | ARCH_VFP_V4_D16 (+EXT_FP16+EXT_FMA)
* | |
* | ARCH_VFP_V4 (+EXT_D32)
* | |
* | ARCH_NEON_VFP_V4 (+EXT_NEON+EXT_NEON_FMA)
* |
* ARCH_VFP_V3 (+EXT_D32)
* |
* +-------------------+
* | |
* | ARCH_VFP_V3_FP16 (+EXT_FP16)
* |
* ARCH_VFP_V3_PLUS_NEON_V1 (+EXT_NEON)
* |
* ARCH_NEON_FP16 (+EXT_FP16)
*
*/
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