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/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
/*
* MSVC wants us to use the non-portable _dupenv_s instead; since we need
* to remain portable, tell MSVC to suppress this warning.
*/
#define _CRT_SECURE_NO_WARNINGS
#include <aws/common/cpuid.h>
#include <stdlib.h>
extern void aws_run_cpuid(uint32_t eax, uint32_t ecx, uint32_t *abcd);
typedef bool(has_feature_fn)(void);
static bool s_has_clmul(void) {
uint32_t abcd[4];
uint32_t clmul_mask = 0x00000002;
aws_run_cpuid(1, 0, abcd);
if ((abcd[2] & clmul_mask) != clmul_mask)
return false;
return true;
}
static bool s_has_sse41(void) {
uint32_t abcd[4];
uint32_t sse41_mask = 0x00080000;
aws_run_cpuid(1, 0, abcd);
if ((abcd[2] & sse41_mask) != sse41_mask)
return false;
return true;
}
static bool s_has_sse42(void) {
uint32_t abcd[4];
uint32_t sse42_mask = 0x00100000;
aws_run_cpuid(1, 0, abcd);
if ((abcd[2] & sse42_mask) != sse42_mask)
return false;
return true;
}
static bool s_has_avx2(void) {
uint32_t abcd[4];
/* Check AVX2:
* CPUID.(EAX=07H, ECX=0H):EBX.AVX2[bit 5]==1 */
uint32_t avx2_mask = (1 << 5);
aws_run_cpuid(7, 0, abcd);
if ((abcd[1] & avx2_mask) != avx2_mask) {
return false;
}
/* Also check AVX:
* CPUID.(EAX=01H, ECX=0H):ECX.AVX[bit 28]==1
*
* NOTE: It SHOULD be impossible for a CPU to support AVX2 without supporting AVX.
* But we've received crash reports where the AVX2 feature check passed
* and then an AVX instruction caused an "invalid instruction" crash.
*
* We diagnosed these machines by asking users to run the sample program from:
* https://docs.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex?view=msvc-160
* and observed the following results:
*
* AVX not supported
* AVX2 supported
*
* We don't know for sure what was up with those machines, but this extra
* check should stop them from running our AVX/AVX2 code paths. */
uint32_t avx1_mask = (1 << 28);
aws_run_cpuid(1, 0, abcd);
if ((abcd[2] & avx1_mask) != avx1_mask) {
return false;
}
return true;
}
static bool s_has_bmi2(void) {
uint32_t abcd[4];
/* Check BMI2:
* CPUID.(EAX=07H, ECX=0H):EBX.BMI2[bit 8]==1 */
uint32_t bmi2_mask = (1 << 8);
aws_run_cpuid(7, 0, abcd);
if ((abcd[1] & bmi2_mask) != bmi2_mask) {
return false;
}
return true;
}
has_feature_fn *s_check_cpu_feature[AWS_CPU_FEATURE_COUNT] = {
[AWS_CPU_FEATURE_CLMUL] = s_has_clmul,
[AWS_CPU_FEATURE_SSE_4_1] = s_has_sse41,
[AWS_CPU_FEATURE_SSE_4_2] = s_has_sse42,
[AWS_CPU_FEATURE_AVX2] = s_has_avx2,
[AWS_CPU_FEATURE_BMI2] = s_has_bmi2,
};
bool aws_cpu_has_feature(enum aws_cpu_feature_name feature_name) {
if (s_check_cpu_feature[feature_name])
return s_check_cpu_feature[feature_name]();
return false;
}
#define CPUID_AVAILABLE 0
#define CPUID_UNAVAILABLE 1
static int cpuid_state = 2;
bool aws_common_private_has_avx2(void) {
if (AWS_LIKELY(cpuid_state == 0)) {
return true;
}
if (AWS_LIKELY(cpuid_state == 1)) {
return false;
}
/* Provide a hook for testing fallbacks and benchmarking */
const char *env_avx2_enabled = getenv("AWS_COMMON_AVX2");
if (env_avx2_enabled) {
int is_enabled = atoi(env_avx2_enabled);
cpuid_state = !is_enabled;
return is_enabled;
}
bool available = aws_cpu_has_feature(AWS_CPU_FEATURE_AVX2);
cpuid_state = available ? CPUID_AVAILABLE : CPUID_UNAVAILABLE;
return available;
}
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