70 lines · cpp
1#include <cassert>2#include <cinttypes>3#include <cstdint>4#include <cstdio>5 6struct alignas(16) float80_raw {7 uint8_t data[10];8};9 10int main() {11 float80_raw st[8];12 uint16_t env[14];13 union alignas(16) {14 uint16_t i16[256];15 uint32_t i32[128];16 uint64_t i64[64];17 } fxsave;18 19 asm volatile(20 "finit\n\t"21 "int3\n\t"22#if defined(__x86_64__)23 "fxsave64 %2\n\t"24#else25 "fxsave %2\n\t"26#endif27 "fnstenv %1\n\t"28 "fnclex\n\t"29 "fstpt 0x00(%0)\n\t"30 "fstpt 0x10(%0)\n\t"31 "fstpt 0x20(%0)\n\t"32 "fstpt 0x30(%0)\n\t"33 "fstpt 0x40(%0)\n\t"34 "fstpt 0x50(%0)\n\t"35 "fstpt 0x60(%0)\n\t"36 "fstpt 0x70(%0)\n\t"37 :38 : "a"(st), "m"(env), "m"(fxsave)39 : "st"40 );41 42 assert(env[0] == fxsave.i16[0]);43 assert(env[2] == fxsave.i16[1]);44 45 printf("fctrl = 0x%04" PRIx16 "\n", env[0]);46 printf("fstat = 0x%04" PRIx16 "\n", env[2]);47 printf("ftag = 0x%04" PRIx16 "\n", env[4]);48 printf("fop = 0x%04" PRIx16 "\n", fxsave.i16[3]);49#if defined(__x86_64__)50 printf("fip = 0x%016" PRIx64 "\n", fxsave.i64[1]);51 printf("fdp = 0x%016" PRIx64 "\n", fxsave.i64[2]);52#else53 printf("fip = 0x%08" PRIx32 "\n", fxsave.i32[2]);54 printf("fcs = 0x%04" PRIx16 "\n", fxsave.i16[6]);55 printf("fdp = 0x%08" PRIx32 "\n", fxsave.i32[4]);56 printf("fds = 0x%04" PRIx16 "\n", fxsave.i16[10]);57#endif58 printf("mxcsr = 0x%08" PRIx32 "\n", fxsave.i32[6]);59 printf("mxcsr_mask = 0x%08" PRIx32 "\n", fxsave.i32[7]);60 61 for (int i = 0; i < 8; ++i) {62 printf("st%d = { ", i);63 for (int j = 0; j < sizeof(st->data); ++j)64 printf("0x%02" PRIx8 " ", st[i].data[j]);65 printf("}\n");66 }67 68 return 0;69}70