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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 #include <cpu-features.h>
     17 #include <setjmp.h>
     18 #include <stdio.h>
     19 #include <signal.h>
     20 
     21 #ifndef __arm__
     22 #error "Only compile this file for an ARM target"
     23 #endif
     24 
     25 static int volatile g_signal_raised;
     26 static sigjmp_buf g_jumper;
     27 
     28 static void my_signal_handler(int signum) {
     29     g_signal_raised = 1;
     30     siglongjmp(g_jumper, 1);
     31 }
     32 
     33 static int32_t do_idiv(int32_t a, int32_t b) {
     34   __asm__ __volatile__(
     35       "sdiv %0, %0, %1\n\t"
     36       : "=&r"(a)
     37       : "r"(b)
     38       : "cc");
     39   return a;
     40 }
     41 
     42 // Check that the ARM idiv instruction is supported.
     43 // Returns 1 on success, 0 otherwise.
     44 static int check_idiv(void) {
     45     // Setup SIGILL signal handler.
     46     struct sigaction old_handler, new_handler;
     47     memset(&new_handler, 0, sizeof(new_handler));
     48     new_handler.sa_handler = my_signal_handler;
     49     sigaction(SIGILL, &new_handler, &old_handler);
     50 
     51     // Do the division.
     52     g_signal_raised = 0;
     53     if (sigsetjmp(g_jumper, 0) == 0)
     54         do_idiv(12345, 17);
     55 
     56     // Restore SIGILL handler.
     57     sigaction(SIGILL, &old_handler, NULL);
     58 
     59     return g_signal_raised == 0;
     60 }
     61 
     62 int main(void)
     63 {
     64     uint32_t cpu_id = android_getCpuIdArm();
     65     printf("cpu-features reports the following CPUID: 0x%08x\n",
     66            cpu_id);
     67 
     68     uint64_t features = android_getCpuFeatures();
     69 #ifdef __thumb2__
     70     const uint64_t idiv_flag = ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2;
     71     const char* variant = "thumb";
     72 #else
     73     const uint64_t idiv_flag = ANDROID_CPU_ARM_FEATURE_IDIV_ARM;
     74     const char* variant = "arm";
     75 #endif
     76 
     77     printf("status of %s idiv instruction:\n", variant);
     78     int idiv_reported = (features & idiv_flag) != 0;
     79     printf("  reported      : %s\n",
     80            idiv_reported ? "supported" : "unsupported");
     81 
     82     int idiv_checked = check_idiv();
     83     printf("  runtime check : %s\n",
     84            idiv_checked ? "supported" : "unsupported");
     85 
     86     return (idiv_reported != idiv_checked);
     87 }
     88