| 1 | /* Beginning of modification history */ |
| 2 | /* Written 02-04-10 by Paul Green (Paul.Green@stratus.com) */ |
| 3 | /* End of modification history */ |
| 4 | |
| 5 | /* This test case is extracted from Perl version 5.7.3. It is |
| 6 | in the Perl_unpack_str function of the pp_pack.c source file. |
| 7 | |
| 8 | GCC 2.95.2 improperly assumes that it can compensate for an |
| 9 | extra fsub by performing a fadd. This would work in |
| 10 | fixed-point arithmetic, but does not work in floating-point |
| 11 | arithmetic. |
| 12 | |
| 13 | This problem has been seen on HP-UX and on Stratus VOS, both |
| 14 | of which have an HP PA-RISC target (hppa1.1). The Stratus |
| 15 | bug number is gnu_g++-220. */ |
| 16 | |
| 17 | /* #define _POSIX_C_SOURCE 199506L -- added by Configure */ |
| 18 | #include <stdio.h> |
| 19 | #include <string.h> |
| 20 | #include <math.h> |
| 21 | |
| 22 | void test(double *result) |
| 23 | { |
| 24 | float afloat; |
| 25 | double adouble; |
| 26 | int checksum = 0; |
| 27 | unsigned cuv = 0; |
| 28 | double cdouble = 0.0; |
| 29 | const int bits_in_uv = 8 * sizeof(cuv); |
| 30 | |
| 31 | checksum = 53; |
| 32 | cdouble = -1.0; |
| 33 | |
| 34 | if (checksum) { |
| 35 | if (checksum > bits_in_uv) { |
| 36 | double trouble; |
| 37 | |
| 38 | adouble = (double) (1 << (checksum & 15)); |
| 39 | |
| 40 | while (checksum >= 16) { |
| 41 | checksum -= 16; |
| 42 | adouble *= 65536.0; |
| 43 | } |
| 44 | |
| 45 | /* At -O1, GCC 2.95.2 compiles the following loop |
| 46 | into: |
| 47 | |
| 48 | L$0014 |
| 49 | fcmp,dbl,>= %fr4,%fr0 |
| 50 | ftest |
| 51 | b L$0014 |
| 52 | fadd,dbl %fr4,%fr12,%fr4 |
| 53 | fsub,dbl %fr4,%fr12,%fr4 |
| 54 | |
| 55 | This code depends on the floading-add and |
| 56 | floating-subtract retaining all of the |
| 57 | precision present in the operands. There is |
| 58 | no such guarantee when using floating-point, |
| 59 | as this test case demonstrates. |
| 60 | |
| 61 | The code is okay at -O0. */ |
| 62 | |
| 63 | while (cdouble < 0.0) |
| 64 | cdouble += adouble; |
| 65 | |
| 66 | cdouble = modf (cdouble / adouble, &trouble) * adouble; |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | *result = cdouble; |
| 71 | } |
| 72 | |
| 73 | int main (int argc, char ** argv) |
| 74 | { |
| 75 | double value; |
| 76 | |
| 77 | test (&value); |
| 78 | |
| 79 | if (argc == 2 && !strcmp(argv[1],"-v")) |
| 80 | printf ("value = %.18e\n", value); |
| 81 | |
| 82 | if (value != 9.007199254740991e+15) { |
| 83 | printf ("t001 fails!\n"); |
| 84 | return -1; |
| 85 | } |
| 86 | else { |
| 87 | printf ("t001 works.\n"); |
| 88 | return 0; |
| 89 | } |
| 90 | } |