summaryrefslogtreecommitdiff
path: root/src/runtime/softfloat64.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/runtime/softfloat64.go')
-rw-r--r--src/runtime/softfloat64.go498
1 files changed, 498 insertions, 0 deletions
diff --git a/src/runtime/softfloat64.go b/src/runtime/softfloat64.go
new file mode 100644
index 000000000..4fcf8f269
--- /dev/null
+++ b/src/runtime/softfloat64.go
@@ -0,0 +1,498 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Software IEEE754 64-bit floating point.
+// Only referred to (and thus linked in) by arm port
+// and by tests in this directory.
+
+package runtime
+
+const (
+ mantbits64 uint = 52
+ expbits64 uint = 11
+ bias64 = -1<<(expbits64-1) + 1
+
+ nan64 uint64 = (1<<expbits64-1)<<mantbits64 + 1
+ inf64 uint64 = (1<<expbits64 - 1) << mantbits64
+ neg64 uint64 = 1 << (expbits64 + mantbits64)
+
+ mantbits32 uint = 23
+ expbits32 uint = 8
+ bias32 = -1<<(expbits32-1) + 1
+
+ nan32 uint32 = (1<<expbits32-1)<<mantbits32 + 1
+ inf32 uint32 = (1<<expbits32 - 1) << mantbits32
+ neg32 uint32 = 1 << (expbits32 + mantbits32)
+)
+
+func funpack64(f uint64) (sign, mant uint64, exp int, inf, nan bool) {
+ sign = f & (1 << (mantbits64 + expbits64))
+ mant = f & (1<<mantbits64 - 1)
+ exp = int(f>>mantbits64) & (1<<expbits64 - 1)
+
+ switch exp {
+ case 1<<expbits64 - 1:
+ if mant != 0 {
+ nan = true
+ return
+ }
+ inf = true
+ return
+
+ case 0:
+ // denormalized
+ if mant != 0 {
+ exp += bias64 + 1
+ for mant < 1<<mantbits64 {
+ mant <<= 1
+ exp--
+ }
+ }
+
+ default:
+ // add implicit top bit
+ mant |= 1 << mantbits64
+ exp += bias64
+ }
+ return
+}
+
+func funpack32(f uint32) (sign, mant uint32, exp int, inf, nan bool) {
+ sign = f & (1 << (mantbits32 + expbits32))
+ mant = f & (1<<mantbits32 - 1)
+ exp = int(f>>mantbits32) & (1<<expbits32 - 1)
+
+ switch exp {
+ case 1<<expbits32 - 1:
+ if mant != 0 {
+ nan = true
+ return
+ }
+ inf = true
+ return
+
+ case 0:
+ // denormalized
+ if mant != 0 {
+ exp += bias32 + 1
+ for mant < 1<<mantbits32 {
+ mant <<= 1
+ exp--
+ }
+ }
+
+ default:
+ // add implicit top bit
+ mant |= 1 << mantbits32
+ exp += bias32
+ }
+ return
+}
+
+func fpack64(sign, mant uint64, exp int, trunc uint64) uint64 {
+ mant0, exp0, trunc0 := mant, exp, trunc
+ if mant == 0 {
+ return sign
+ }
+ for mant < 1<<mantbits64 {
+ mant <<= 1
+ exp--
+ }
+ for mant >= 4<<mantbits64 {
+ trunc |= mant & 1
+ mant >>= 1
+ exp++
+ }
+ if mant >= 2<<mantbits64 {
+ if mant&1 != 0 && (trunc != 0 || mant&2 != 0) {
+ mant++
+ if mant >= 4<<mantbits64 {
+ mant >>= 1
+ exp++
+ }
+ }
+ mant >>= 1
+ exp++
+ }
+ if exp >= 1<<expbits64-1+bias64 {
+ return sign ^ inf64
+ }
+ if exp < bias64+1 {
+ if exp < bias64-int(mantbits64) {
+ return sign | 0
+ }
+ // repeat expecting denormal
+ mant, exp, trunc = mant0, exp0, trunc0
+ for exp < bias64 {
+ trunc |= mant & 1
+ mant >>= 1
+ exp++
+ }
+ if mant&1 != 0 && (trunc != 0 || mant&2 != 0) {
+ mant++
+ }
+ mant >>= 1
+ exp++
+ if mant < 1<<mantbits64 {
+ return sign | mant
+ }
+ }
+ return sign | uint64(exp-bias64)<<mantbits64 | mant&(1<<mantbits64-1)
+}
+
+func fpack32(sign, mant uint32, exp int, trunc uint32) uint32 {
+ mant0, exp0, trunc0 := mant, exp, trunc
+ if mant == 0 {
+ return sign
+ }
+ for mant < 1<<mantbits32 {
+ mant <<= 1
+ exp--
+ }
+ for mant >= 4<<mantbits32 {
+ trunc |= mant & 1
+ mant >>= 1
+ exp++
+ }
+ if mant >= 2<<mantbits32 {
+ if mant&1 != 0 && (trunc != 0 || mant&2 != 0) {
+ mant++
+ if mant >= 4<<mantbits32 {
+ mant >>= 1
+ exp++
+ }
+ }
+ mant >>= 1
+ exp++
+ }
+ if exp >= 1<<expbits32-1+bias32 {
+ return sign ^ inf32
+ }
+ if exp < bias32+1 {
+ if exp < bias32-int(mantbits32) {
+ return sign | 0
+ }
+ // repeat expecting denormal
+ mant, exp, trunc = mant0, exp0, trunc0
+ for exp < bias32 {
+ trunc |= mant & 1
+ mant >>= 1
+ exp++
+ }
+ if mant&1 != 0 && (trunc != 0 || mant&2 != 0) {
+ mant++
+ }
+ mant >>= 1
+ exp++
+ if mant < 1<<mantbits32 {
+ return sign | mant
+ }
+ }
+ return sign | uint32(exp-bias32)<<mantbits32 | mant&(1<<mantbits32-1)
+}
+
+func fadd64(f, g uint64) uint64 {
+ fs, fm, fe, fi, fn := funpack64(f)
+ gs, gm, ge, gi, gn := funpack64(g)
+
+ // Special cases.
+ switch {
+ case fn || gn: // NaN + x or x + NaN = NaN
+ return nan64
+
+ case fi && gi && fs != gs: // +Inf + -Inf or -Inf + +Inf = NaN
+ return nan64
+
+ case fi: // ±Inf + g = ±Inf
+ return f
+
+ case gi: // f + ±Inf = ±Inf
+ return g
+
+ case fm == 0 && gm == 0 && fs != 0 && gs != 0: // -0 + -0 = -0
+ return f
+
+ case fm == 0: // 0 + g = g but 0 + -0 = +0
+ if gm == 0 {
+ g ^= gs
+ }
+ return g
+
+ case gm == 0: // f + 0 = f
+ return f
+
+ }
+
+ if fe < ge || fe == ge && fm < gm {
+ f, g, fs, fm, fe, gs, gm, ge = g, f, gs, gm, ge, fs, fm, fe
+ }
+
+ shift := uint(fe - ge)
+ fm <<= 2
+ gm <<= 2
+ trunc := gm & (1<<shift - 1)
+ gm >>= shift
+ if fs == gs {
+ fm += gm
+ } else {
+ fm -= gm
+ if trunc != 0 {
+ fm--
+ }
+ }
+ if fm == 0 {
+ fs = 0
+ }
+ return fpack64(fs, fm, fe-2, trunc)
+}
+
+func fsub64(f, g uint64) uint64 {
+ return fadd64(f, fneg64(g))
+}
+
+func fneg64(f uint64) uint64 {
+ return f ^ (1 << (mantbits64 + expbits64))
+}
+
+func fmul64(f, g uint64) uint64 {
+ fs, fm, fe, fi, fn := funpack64(f)
+ gs, gm, ge, gi, gn := funpack64(g)
+
+ // Special cases.
+ switch {
+ case fn || gn: // NaN * g or f * NaN = NaN
+ return nan64
+
+ case fi && gi: // Inf * Inf = Inf (with sign adjusted)
+ return f ^ gs
+
+ case fi && gm == 0, fm == 0 && gi: // 0 * Inf = Inf * 0 = NaN
+ return nan64
+
+ case fm == 0: // 0 * x = 0 (with sign adjusted)
+ return f ^ gs
+
+ case gm == 0: // x * 0 = 0 (with sign adjusted)
+ return g ^ fs
+ }
+
+ // 53-bit * 53-bit = 107- or 108-bit
+ lo, hi := mullu(fm, gm)
+ shift := mantbits64 - 1
+ trunc := lo & (1<<shift - 1)
+ mant := hi<<(64-shift) | lo>>shift
+ return fpack64(fs^gs, mant, fe+ge-1, trunc)
+}
+
+func fdiv64(f, g uint64) uint64 {
+ fs, fm, fe, fi, fn := funpack64(f)
+ gs, gm, ge, gi, gn := funpack64(g)
+
+ // Special cases.
+ switch {
+ case fn || gn: // NaN / g = f / NaN = NaN
+ return nan64
+
+ case fi && gi: // ±Inf / ±Inf = NaN
+ return nan64
+
+ case !fi && !gi && fm == 0 && gm == 0: // 0 / 0 = NaN
+ return nan64
+
+ case fi, !gi && gm == 0: // Inf / g = f / 0 = Inf
+ return fs ^ gs ^ inf64
+
+ case gi, fm == 0: // f / Inf = 0 / g = Inf
+ return fs ^ gs ^ 0
+ }
+ _, _, _, _ = fi, fn, gi, gn
+
+ // 53-bit<<54 / 53-bit = 53- or 54-bit.
+ shift := mantbits64 + 2
+ q, r := divlu(fm>>(64-shift), fm<<shift, gm)
+ return fpack64(fs^gs, q, fe-ge-2, r)
+}
+
+func f64to32(f uint64) uint32 {
+ fs, fm, fe, fi, fn := funpack64(f)
+ if fn {
+ return nan32
+ }
+ fs32 := uint32(fs >> 32)
+ if fi {
+ return fs32 ^ inf32
+ }
+ const d = mantbits64 - mantbits32 - 1
+ return fpack32(fs32, uint32(fm>>d), fe-1, uint32(fm&(1<<d-1)))
+}
+
+func f32to64(f uint32) uint64 {
+ const d = mantbits64 - mantbits32
+ fs, fm, fe, fi, fn := funpack32(f)
+ if fn {
+ return nan64
+ }
+ fs64 := uint64(fs) << 32
+ if fi {
+ return fs64 ^ inf64
+ }
+ return fpack64(fs64, uint64(fm)<<d, fe, 0)
+}
+
+func fcmp64(f, g uint64) (cmp int, isnan bool) {
+ fs, fm, _, fi, fn := funpack64(f)
+ gs, gm, _, gi, gn := funpack64(g)
+
+ switch {
+ case fn, gn: // flag NaN
+ return 0, true
+
+ case !fi && !gi && fm == 0 && gm == 0: // ±0 == ±0
+ return 0, false
+
+ case fs > gs: // f < 0, g > 0
+ return -1, false
+
+ case fs < gs: // f > 0, g < 0
+ return +1, false
+
+ // Same sign, not NaN.
+ // Can compare encodings directly now.
+ // Reverse for sign.
+ case fs == 0 && f < g, fs != 0 && f > g:
+ return -1, false
+
+ case fs == 0 && f > g, fs != 0 && f < g:
+ return +1, false
+ }
+
+ // f == g
+ return 0, false
+}
+
+func f64toint(f uint64) (val int64, ok bool) {
+ fs, fm, fe, fi, fn := funpack64(f)
+
+ switch {
+ case fi, fn: // NaN
+ return 0, false
+
+ case fe < -1: // f < 0.5
+ return 0, false
+
+ case fe > 63: // f >= 2^63
+ if fs != 0 && fm == 0 { // f == -2^63
+ return -1 << 63, true
+ }
+ if fs != 0 {
+ return 0, false
+ }
+ return 0, false
+ }
+
+ for fe > int(mantbits64) {
+ fe--
+ fm <<= 1
+ }
+ for fe < int(mantbits64) {
+ fe++
+ fm >>= 1
+ }
+ val = int64(fm)
+ if fs != 0 {
+ val = -val
+ }
+ return val, true
+}
+
+func fintto64(val int64) (f uint64) {
+ fs := uint64(val) & (1 << 63)
+ mant := uint64(val)
+ if fs != 0 {
+ mant = -mant
+ }
+ return fpack64(fs, mant, int(mantbits64), 0)
+}
+
+// 64x64 -> 128 multiply.
+// adapted from hacker's delight.
+func mullu(u, v uint64) (lo, hi uint64) {
+ const (
+ s = 32
+ mask = 1<<s - 1
+ )
+ u0 := u & mask
+ u1 := u >> s
+ v0 := v & mask
+ v1 := v >> s
+ w0 := u0 * v0
+ t := u1*v0 + w0>>s
+ w1 := t & mask
+ w2 := t >> s
+ w1 += u0 * v1
+ return u * v, u1*v1 + w2 + w1>>s
+}
+
+// 128/64 -> 64 quotient, 64 remainder.
+// adapted from hacker's delight
+func divlu(u1, u0, v uint64) (q, r uint64) {
+ const b = 1 << 32
+
+ if u1 >= v {
+ return 1<<64 - 1, 1<<64 - 1
+ }
+
+ // s = nlz(v); v <<= s
+ s := uint(0)
+ for v&(1<<63) == 0 {
+ s++
+ v <<= 1
+ }
+
+ vn1 := v >> 32
+ vn0 := v & (1<<32 - 1)
+ un32 := u1<<s | u0>>(64-s)
+ un10 := u0 << s
+ un1 := un10 >> 32
+ un0 := un10 & (1<<32 - 1)
+ q1 := un32 / vn1
+ rhat := un32 - q1*vn1
+
+again1:
+ if q1 >= b || q1*vn0 > b*rhat+un1 {
+ q1--
+ rhat += vn1
+ if rhat < b {
+ goto again1
+ }
+ }
+
+ un21 := un32*b + un1 - q1*v
+ q0 := un21 / vn1
+ rhat = un21 - q0*vn1
+
+again2:
+ if q0 >= b || q0*vn0 > b*rhat+un0 {
+ q0--
+ rhat += vn1
+ if rhat < b {
+ goto again2
+ }
+ }
+
+ return q1*b + q0, (un21*b + un0 - q0*v) >> s
+}
+
+// callable from C
+
+func fadd64c(f, g uint64, ret *uint64) { *ret = fadd64(f, g) }
+func fsub64c(f, g uint64, ret *uint64) { *ret = fsub64(f, g) }
+func fmul64c(f, g uint64, ret *uint64) { *ret = fmul64(f, g) }
+func fdiv64c(f, g uint64, ret *uint64) { *ret = fdiv64(f, g) }
+func fneg64c(f uint64, ret *uint64) { *ret = fneg64(f) }
+func f32to64c(f uint32, ret *uint64) { *ret = f32to64(f) }
+func f64to32c(f uint64, ret *uint32) { *ret = f64to32(f) }
+func fcmp64c(f, g uint64, ret *int, retnan *bool) { *ret, *retnan = fcmp64(f, g) }
+func fintto64c(val int64, ret *uint64) { *ret = fintto64(val) }
+func f64tointc(f uint64, ret *int64, retok *bool) { *ret, *retok = f64toint(f) }
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-17 22:13:26 +0000