1//===-- lib/addsf3.c - Single-precision addition ------------------*- C -*-===//
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 single-precision soft-float addition with the IEEE-754
11// default rounding (to nearest, ties to even).
12//
13//===----------------------------------------------------------------------===//
14
15#define SINGLE_PRECISION
16#include "fp_lib.h"
17
| 1//===-- lib/addsf3.c - Single-precision addition ------------------*- C -*-===//
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 single-precision soft-float addition with the IEEE-754
11// default rounding (to nearest, ties to even).
12//
13//===----------------------------------------------------------------------===//
14
15#define SINGLE_PRECISION
16#include "fp_lib.h"
17
|
18ARM_EABI_FNALIAS(fadd, addsf3);
| 18ARM_EABI_FNALIAS(fadd, addsf3)
|
19
20fp_t __addsf3(fp_t a, fp_t b) {
21
22 rep_t aRep = toRep(a);
23 rep_t bRep = toRep(b);
24 const rep_t aAbs = aRep & absMask;
25 const rep_t bAbs = bRep & absMask;
26
27 // Detect if a or b is zero, infinity, or NaN.
28 if (aAbs - 1U >= infRep - 1U || bAbs - 1U >= infRep - 1U) {
29
30 // NaN + anything = qNaN
31 if (aAbs > infRep) return fromRep(toRep(a) | quietBit);
32 // anything + NaN = qNaN
33 if (bAbs > infRep) return fromRep(toRep(b) | quietBit);
34
35 if (aAbs == infRep) {
36 // +/-infinity + -/+infinity = qNaN
37 if ((toRep(a) ^ toRep(b)) == signBit) return fromRep(qnanRep);
38 // +/-infinity + anything remaining = +/- infinity
39 else return a;
40 }
41
42 // anything remaining + +/-infinity = +/-infinity
43 if (bAbs == infRep) return b;
44
45 // zero + anything = anything
46 if (!aAbs) {
47 // but we need to get the sign right for zero + zero
48 if (!bAbs) return fromRep(toRep(a) & toRep(b));
49 else return b;
50 }
51
52 // anything + zero = anything
53 if (!bAbs) return a;
54 }
55
56 // Swap a and b if necessary so that a has the larger absolute value.
57 if (bAbs > aAbs) {
58 const rep_t temp = aRep;
59 aRep = bRep;
60 bRep = temp;
61 }
62
63 // Extract the exponent and significand from the (possibly swapped) a and b.
64 int aExponent = aRep >> significandBits & maxExponent;
65 int bExponent = bRep >> significandBits & maxExponent;
66 rep_t aSignificand = aRep & significandMask;
67 rep_t bSignificand = bRep & significandMask;
68
69 // Normalize any denormals, and adjust the exponent accordingly.
70 if (aExponent == 0) aExponent = normalize(&aSignificand);
71 if (bExponent == 0) bExponent = normalize(&bSignificand);
72
73 // The sign of the result is the sign of the larger operand, a. If they
74 // have opposite signs, we are performing a subtraction; otherwise addition.
75 const rep_t resultSign = aRep & signBit;
76 const bool subtraction = (aRep ^ bRep) & signBit;
77
78 // Shift the significands to give us round, guard and sticky, and or in the
79 // implicit significand bit. (If we fell through from the denormal path it
80 // was already set by normalize( ), but setting it twice won't hurt
81 // anything.)
82 aSignificand = (aSignificand | implicitBit) << 3;
83 bSignificand = (bSignificand | implicitBit) << 3;
84
85 // Shift the significand of b by the difference in exponents, with a sticky
86 // bottom bit to get rounding correct.
| 19
20fp_t __addsf3(fp_t a, fp_t b) {
21
22 rep_t aRep = toRep(a);
23 rep_t bRep = toRep(b);
24 const rep_t aAbs = aRep & absMask;
25 const rep_t bAbs = bRep & absMask;
26
27 // Detect if a or b is zero, infinity, or NaN.
28 if (aAbs - 1U >= infRep - 1U || bAbs - 1U >= infRep - 1U) {
29
30 // NaN + anything = qNaN
31 if (aAbs > infRep) return fromRep(toRep(a) | quietBit);
32 // anything + NaN = qNaN
33 if (bAbs > infRep) return fromRep(toRep(b) | quietBit);
34
35 if (aAbs == infRep) {
36 // +/-infinity + -/+infinity = qNaN
37 if ((toRep(a) ^ toRep(b)) == signBit) return fromRep(qnanRep);
38 // +/-infinity + anything remaining = +/- infinity
39 else return a;
40 }
41
42 // anything remaining + +/-infinity = +/-infinity
43 if (bAbs == infRep) return b;
44
45 // zero + anything = anything
46 if (!aAbs) {
47 // but we need to get the sign right for zero + zero
48 if (!bAbs) return fromRep(toRep(a) & toRep(b));
49 else return b;
50 }
51
52 // anything + zero = anything
53 if (!bAbs) return a;
54 }
55
56 // Swap a and b if necessary so that a has the larger absolute value.
57 if (bAbs > aAbs) {
58 const rep_t temp = aRep;
59 aRep = bRep;
60 bRep = temp;
61 }
62
63 // Extract the exponent and significand from the (possibly swapped) a and b.
64 int aExponent = aRep >> significandBits & maxExponent;
65 int bExponent = bRep >> significandBits & maxExponent;
66 rep_t aSignificand = aRep & significandMask;
67 rep_t bSignificand = bRep & significandMask;
68
69 // Normalize any denormals, and adjust the exponent accordingly.
70 if (aExponent == 0) aExponent = normalize(&aSignificand);
71 if (bExponent == 0) bExponent = normalize(&bSignificand);
72
73 // The sign of the result is the sign of the larger operand, a. If they
74 // have opposite signs, we are performing a subtraction; otherwise addition.
75 const rep_t resultSign = aRep & signBit;
76 const bool subtraction = (aRep ^ bRep) & signBit;
77
78 // Shift the significands to give us round, guard and sticky, and or in the
79 // implicit significand bit. (If we fell through from the denormal path it
80 // was already set by normalize( ), but setting it twice won't hurt
81 // anything.)
82 aSignificand = (aSignificand | implicitBit) << 3;
83 bSignificand = (bSignificand | implicitBit) << 3;
84
85 // Shift the significand of b by the difference in exponents, with a sticky
86 // bottom bit to get rounding correct.
|
87 const int align = aExponent - bExponent;
| 87 const unsigned int align = aExponent - bExponent;
|
88 if (align) {
89 if (align < typeWidth) {
90 const bool sticky = bSignificand << (typeWidth - align);
91 bSignificand = bSignificand >> align | sticky;
92 } else {
93 bSignificand = 1; // sticky; b is known to be non-zero.
94 }
95 }
96
97 if (subtraction) {
98 aSignificand -= bSignificand;
99
100 // If a == -b, return +zero.
101 if (aSignificand == 0) return fromRep(0);
102
103 // If partial cancellation occured, we need to left-shift the result
104 // and adjust the exponent:
105 if (aSignificand < implicitBit << 3) {
106 const int shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3);
107 aSignificand <<= shift;
108 aExponent -= shift;
109 }
110 }
111
112 else /* addition */ {
113 aSignificand += bSignificand;
114
115 // If the addition carried up, we need to right-shift the result and
116 // adjust the exponent:
117 if (aSignificand & implicitBit << 4) {
118 const bool sticky = aSignificand & 1;
119 aSignificand = aSignificand >> 1 | sticky;
120 aExponent += 1;
121 }
122 }
123
124 // If we have overflowed the type, return +/- infinity:
125 if (aExponent >= maxExponent) return fromRep(infRep | resultSign);
126
127 if (aExponent <= 0) {
128 // Result is denormal before rounding; the exponent is zero and we
129 // need to shift the significand.
130 const int shift = 1 - aExponent;
131 const bool sticky = aSignificand << (typeWidth - shift);
132 aSignificand = aSignificand >> shift | sticky;
133 aExponent = 0;
134 }
135
136 // Low three bits are round, guard, and sticky.
137 const int roundGuardSticky = aSignificand & 0x7;
138
139 // Shift the significand into place, and mask off the implicit bit.
140 rep_t result = aSignificand >> 3 & significandMask;
141
142 // Insert the exponent and sign.
143 result |= (rep_t)aExponent << significandBits;
144 result |= resultSign;
145
146 // Final rounding. The result may overflow to infinity, but that is the
147 // correct result in that case.
148 if (roundGuardSticky > 0x4) result++;
149 if (roundGuardSticky == 0x4) result += result & 1;
150 return fromRep(result);
151}
| 88 if (align) {
89 if (align < typeWidth) {
90 const bool sticky = bSignificand << (typeWidth - align);
91 bSignificand = bSignificand >> align | sticky;
92 } else {
93 bSignificand = 1; // sticky; b is known to be non-zero.
94 }
95 }
96
97 if (subtraction) {
98 aSignificand -= bSignificand;
99
100 // If a == -b, return +zero.
101 if (aSignificand == 0) return fromRep(0);
102
103 // If partial cancellation occured, we need to left-shift the result
104 // and adjust the exponent:
105 if (aSignificand < implicitBit << 3) {
106 const int shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3);
107 aSignificand <<= shift;
108 aExponent -= shift;
109 }
110 }
111
112 else /* addition */ {
113 aSignificand += bSignificand;
114
115 // If the addition carried up, we need to right-shift the result and
116 // adjust the exponent:
117 if (aSignificand & implicitBit << 4) {
118 const bool sticky = aSignificand & 1;
119 aSignificand = aSignificand >> 1 | sticky;
120 aExponent += 1;
121 }
122 }
123
124 // If we have overflowed the type, return +/- infinity:
125 if (aExponent >= maxExponent) return fromRep(infRep | resultSign);
126
127 if (aExponent <= 0) {
128 // Result is denormal before rounding; the exponent is zero and we
129 // need to shift the significand.
130 const int shift = 1 - aExponent;
131 const bool sticky = aSignificand << (typeWidth - shift);
132 aSignificand = aSignificand >> shift | sticky;
133 aExponent = 0;
134 }
135
136 // Low three bits are round, guard, and sticky.
137 const int roundGuardSticky = aSignificand & 0x7;
138
139 // Shift the significand into place, and mask off the implicit bit.
140 rep_t result = aSignificand >> 3 & significandMask;
141
142 // Insert the exponent and sign.
143 result |= (rep_t)aExponent << significandBits;
144 result |= resultSign;
145
146 // Final rounding. The result may overflow to infinity, but that is the
147 // correct result in that case.
148 if (roundGuardSticky > 0x4) result++;
149 if (roundGuardSticky == 0x4) result += result & 1;
150 return fromRep(result);
151}
|