Stephen Canon | 5c6d2ec | 2010-07-01 17:58:24 +0000 | [diff] [blame] | 1 | //===-- lib/mulsf3.c - Single-precision multiplication ------------*- C -*-===// |
| 2 | // |
| 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
Howard Hinnant | 9ad441f | 2010-11-16 22:13:33 +0000 | [diff] [blame] | 5 | // This file is dual licensed under the MIT and the University of Illinois Open |
| 6 | // Source Licenses. See LICENSE.TXT for details. |
Stephen Canon | 5c6d2ec | 2010-07-01 17:58:24 +0000 | [diff] [blame] | 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // This file implements single-precision soft-float multiplication |
| 11 | // with the IEEE-754 default rounding (to nearest, ties to even). |
| 12 | // |
| 13 | //===----------------------------------------------------------------------===// |
Anton Korobeynikov | 1c5f89b | 2011-04-19 17:52:09 +0000 | [diff] [blame^] | 14 | #include "abi.h" |
Stephen Canon | e508632 | 2010-07-01 15:52:42 +0000 | [diff] [blame] | 15 | |
| 16 | #define SINGLE_PRECISION |
| 17 | #include "fp_lib.h" |
| 18 | |
Anton Korobeynikov | 37b97d1 | 2011-04-19 17:51:24 +0000 | [diff] [blame] | 19 | ARM_EABI_FNALIAS(fmul, mulsf3); |
| 20 | |
Anton Korobeynikov | 1c5f89b | 2011-04-19 17:52:09 +0000 | [diff] [blame^] | 21 | COMPILER_RT_ABI fp_t |
| 22 | __mulsf3(fp_t a, fp_t b) { |
Stephen Canon | e508632 | 2010-07-01 15:52:42 +0000 | [diff] [blame] | 23 | |
| 24 | const unsigned int aExponent = toRep(a) >> significandBits & maxExponent; |
| 25 | const unsigned int bExponent = toRep(b) >> significandBits & maxExponent; |
| 26 | const rep_t productSign = (toRep(a) ^ toRep(b)) & signBit; |
| 27 | |
| 28 | rep_t aSignificand = toRep(a) & significandMask; |
| 29 | rep_t bSignificand = toRep(b) & significandMask; |
| 30 | int scale = 0; |
| 31 | |
| 32 | // Detect if a or b is zero, denormal, infinity, or NaN. |
| 33 | if (aExponent-1U >= maxExponent-1U || bExponent-1U >= maxExponent-1U) { |
| 34 | |
| 35 | const rep_t aAbs = toRep(a) & absMask; |
| 36 | const rep_t bAbs = toRep(b) & absMask; |
| 37 | |
| 38 | // NaN * anything = qNaN |
| 39 | if (aAbs > infRep) return fromRep(toRep(a) | quietBit); |
| 40 | // anything * NaN = qNaN |
| 41 | if (bAbs > infRep) return fromRep(toRep(b) | quietBit); |
| 42 | |
| 43 | if (aAbs == infRep) { |
| 44 | // infinity * non-zero = +/- infinity |
| 45 | if (bAbs) return fromRep(aAbs | productSign); |
| 46 | // infinity * zero = NaN |
| 47 | else return fromRep(qnanRep); |
| 48 | } |
| 49 | |
| 50 | if (bAbs == infRep) { |
| 51 | // non-zero * infinity = +/- infinity |
| 52 | if (aAbs) return fromRep(bAbs | productSign); |
| 53 | // zero * infinity = NaN |
| 54 | else return fromRep(qnanRep); |
| 55 | } |
| 56 | |
| 57 | // zero * anything = +/- zero |
| 58 | if (!aAbs) return fromRep(productSign); |
| 59 | // anything * zero = +/- zero |
| 60 | if (!bAbs) return fromRep(productSign); |
| 61 | |
| 62 | // one or both of a or b is denormal, the other (if applicable) is a |
| 63 | // normal number. Renormalize one or both of a and b, and set scale to |
| 64 | // include the necessary exponent adjustment. |
| 65 | if (aAbs < implicitBit) scale += normalize(&aSignificand); |
| 66 | if (bAbs < implicitBit) scale += normalize(&bSignificand); |
| 67 | } |
| 68 | |
| 69 | // Or in the implicit significand bit. (If we fell through from the |
| 70 | // denormal path it was already set by normalize( ), but setting it twice |
| 71 | // won't hurt anything.) |
| 72 | aSignificand |= implicitBit; |
| 73 | bSignificand |= implicitBit; |
| 74 | |
| 75 | // Get the significand of a*b. Before multiplying the significands, shift |
| 76 | // one of them left to left-align it in the field. Thus, the product will |
| 77 | // have (exponentBits + 2) integral digits, all but two of which must be |
| 78 | // zero. Normalizing this result is just a conditional left-shift by one |
| 79 | // and bumping the exponent accordingly. |
| 80 | rep_t productHi, productLo; |
| 81 | wideMultiply(aSignificand, bSignificand << exponentBits, |
| 82 | &productHi, &productLo); |
| 83 | |
| 84 | int productExponent = aExponent + bExponent - exponentBias + scale; |
| 85 | |
| 86 | // Normalize the significand, adjust exponent if needed. |
| 87 | if (productHi & implicitBit) productExponent++; |
| 88 | else wideLeftShift(&productHi, &productLo, 1); |
| 89 | |
| 90 | // If we have overflowed the type, return +/- infinity. |
| 91 | if (productExponent >= maxExponent) return fromRep(infRep | productSign); |
| 92 | |
| 93 | if (productExponent <= 0) { |
| 94 | // Result is denormal before rounding, the exponent is zero and we |
| 95 | // need to shift the significand. |
| 96 | wideRightShiftWithSticky(&productHi, &productLo, 1 - productExponent); |
| 97 | } |
| 98 | |
| 99 | else { |
| 100 | // Result is normal before rounding; insert the exponent. |
| 101 | productHi &= significandMask; |
| 102 | productHi |= (rep_t)productExponent << significandBits; |
| 103 | } |
| 104 | |
| 105 | // Insert the sign of the result: |
| 106 | productHi |= productSign; |
| 107 | |
| 108 | // Final rounding. The final result may overflow to infinity, or underflow |
| 109 | // to zero, but those are the correct results in those cases. |
| 110 | if (productLo > signBit) productHi++; |
| 111 | if (productLo == signBit) productHi += productHi & 1; |
| 112 | return fromRep(productHi); |
| 113 | } |