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c50b6f56 PG |
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 | ||
dca46f05 | 55 | This code depends on the floating-add and |
c50b6f56 PG |
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 | } |