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# compiler-rt/trunk/lib/builtins/floatuntitf.c

1 | //===-- lib/floatuntitf.c - uint128 -> quad-precision conversion --*- C -*-===// | ||||
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2 | // | ||||

3 | // The LLVM Compiler Infrastructure | ||||

4 | // | ||||

5 | // This file is dual licensed under the MIT and the University of Illinois Open | ||||

6 | // Source Licenses. See LICENSE.TXT for details. | ||||

7 | // | ||||

8 | //===----------------------------------------------------------------------===// | ||||

9 | // | ||||

10 | // This file implements tu_int to quad-precision conversion for the | ||||

11 | // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even | ||||

12 | // mode. | ||||

13 | // | ||||

14 | //===----------------------------------------------------------------------===// | ||||

15 | | ||||

16 | #define QUAD_PRECISION | ||||

17 | #include "fp_lib.h" | ||||

18 | #include "int_lib.h" | ||||

19 | | ||||

20 | /* Returns: convert a tu_int to a fp_t, rounding toward even. */ | ||||

21 | | ||||

22 | /* Assumption: fp_t is a IEEE 128 bit floating point type | ||||

23 | * tu_int is a 128 bit integral type | ||||

24 | */ | ||||

25 | | ||||

26 | /* seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | | ||||

27 | * mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | ||||

28 | */ | ||||

29 | | ||||

30 | #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT) | ||||

31 | COMPILER_RT_ABI fp_t | ||||

32 | __floatuntitf(tu_int a) { | ||||

33 | if (a == 0) | ||||

34 | return 0.0; | ||||

35 | const unsigned N = sizeof(tu_int) * CHAR_BIT; | ||||

36 | int sd = N - __clzti2(a); /* number of significant digits */ | ||||

37 | int e = sd - 1; /* exponent */ | ||||

38 | if (sd > LDBL_MANT_DIG) { | ||||

39 | /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx | ||||

40 | * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR | ||||

41 | * 12345678901234567890123456 | ||||

42 | * 1 = msb 1 bit | ||||

43 | * P = bit LDBL_MANT_DIG-1 bits to the right of 1 | ||||

44 | * Q = bit LDBL_MANT_DIG bits to the right of 1 | ||||

45 | * R = "or" of all bits to the right of Q | ||||

46 | */ | ||||

47 | switch (sd) { | ||||

48 | case LDBL_MANT_DIG + 1: | ||||

49 | a <<= 1; | ||||

50 | break; | ||||

51 | case LDBL_MANT_DIG + 2: | ||||

52 | break; | ||||

53 | default: | ||||

54 | a = (a >> (sd - (LDBL_MANT_DIG+2))) | | ||||

55 | ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG+2) - sd))) != 0); | ||||

56 | }; | ||||

57 | /* finish: */ | ||||

58 | a |= (a & 4) != 0; /* Or P into R */ | ||||

59 | ++a; /* round - this step may add a significant bit */ | ||||

60 | a >>= 2; /* dump Q and R */ | ||||

61 | /* a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */ | ||||

62 | if (a & ((tu_int)1 << LDBL_MANT_DIG)) { | ||||

63 | a >>= 1; | ||||

64 | ++e; | ||||

65 | } | ||||

66 | /* a is now rounded to LDBL_MANT_DIG bits */ | ||||

67 | } else { | ||||

68 | a <<= (LDBL_MANT_DIG - sd); | ||||

69 | /* a is now rounded to LDBL_MANT_DIG bits */ | ||||

70 | } | ||||

71 | | ||||

72 | long_double_bits fb; | ||||

73 | fb.u.high.all = (du_int)(e + 16383) << 48 /* exponent */ | ||||

74 | | ((a >> 64) & 0x0000ffffffffffffLL); /* significand */ | ||||

75 | fb.u.low.all = (du_int)(a); | ||||

76 | return fb.f; | ||||

77 | } | ||||

78 | | ||||

79 | #endif |