1
0
mirror of https://github.com/golang/go synced 2024-11-21 18:04:40 -07:00

identical complex implementation

for 6g and 8g. can also be used
for 5g. 5g is still a stub.

R=rsc
CC=golang-dev
https://golang.org/cl/362041
This commit is contained in:
Ken Thompson 2010-03-09 12:49:24 -08:00
parent 5b1a196c37
commit f229c8b546
19 changed files with 274 additions and 268 deletions

View File

@ -38,3 +38,6 @@ clean:
install: $(TARG)
cp $(TARG) "$(GOBIN)"/$(TARG)
%.$O: ../gc/%.c
$(CC) $(CFLAGS) -c -I. -o $@ ../gc/$*.c

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@ -134,12 +134,12 @@ void nodfconst(Node*, Type*, Mpflt*);
* cplx.c
*/
int complexop(Node*, Node*);
void complexmove(Node*, Node*, int);
void complexmove(Node*, Node*);
void complexgen(Node*, Node*);
void complexbool(int, Node*, Node*, int, Prog*);
/*
* obj.c
* gobj.c
*/
void datastring(char*, int, Addr*);

View File

@ -483,7 +483,7 @@ gmove(Node *f, Node *t)
cvt = t->type;
if(iscomplex[ft] || iscomplex[tt]) {
complexmove(f, t, 0);
complexmove(f, t);
return;
}

View File

@ -22,6 +22,7 @@ OFILES=\
gsubr.$O\
cgen.$O\
cgen64.$O\
cplx.$O\
peep.$O\
reg.$O\
@ -38,3 +39,6 @@ clean:
install: $(TARG)
cp $(TARG) "$(GOBIN)"/$(TARG)
%.$O: ../gc/%.c
$(CC) $(CFLAGS) -c -I. -o $@ ../gc/$*.c

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@ -57,12 +57,6 @@ cgen(Node *n, Node *res)
if(res == N || res->type == T)
fatal("cgen: res nil");
// TODO compile complex
if(n != N && n->type != T && iscomplex[n->type->etype])
return;
if(res != N && res->type != T && iscomplex[res->type->etype])
return;
// inline slices
if(cgen_inline(n, res))
return;
@ -98,6 +92,12 @@ cgen(Node *n, Node *res)
break;
}
// complex types
if(complexop(n, res)) {
complexgen(n, res);
return;
}
// if both are addressable, move
if(n->addable && res->addable) {
gmove(n, res);
@ -741,12 +741,6 @@ bgen(Node *n, int true, Prog *to)
nl = n->left;
nr = n->right;
// TODO compile complex
if(nl != N && nl->type != T && iscomplex[nl->type->etype])
return;
if(nr != N && nr->type != T && iscomplex[nr->type->etype])
return;
if(n->type == T) {
convlit(&n, types[TBOOL]);
if(n->type == T)
@ -857,6 +851,7 @@ bgen(Node *n, int true, Prog *to)
break;
}
a = brcom(a);
true = !true;
}
// make simplest on right
@ -960,6 +955,10 @@ bgen(Node *n, int true, Prog *to)
patch(gbranch(optoas(a, nr->type), T), to);
break;
}
if(iscomplex[nl->type->etype]) {
complexbool(a, nl, nr, true, to);
break;
}
if(is64(nr->type)) {
if(!nl->addable) {

View File

@ -157,6 +157,14 @@ void split64(Node*, Node*, Node*);
void splitclean(void);
void nswap(Node*, Node*);
/*
* cplx.c
*/
int complexop(Node*, Node*);
void complexmove(Node*, Node*);
void complexgen(Node*, Node*);
void complexbool(int, Node*, Node*, int, Prog*);
/*
* gobj.c
*/

View File

@ -1059,6 +1059,11 @@ gmove(Node *f, Node *t)
tt = simsimtype(t->type);
cvt = t->type;
if(iscomplex[ft] || iscomplex[tt]) {
complexmove(f, t);
return;
}
// cannot have two integer memory operands;
// except 64-bit, which always copies via registers anyway.
if(isint[ft] && isint[tt] && !is64(f->type) && !is64(t->type) && ismem(f) && ismem(t))
@ -1489,13 +1494,13 @@ gmove(Node *f, Node *t)
// on the floating point stack. So toss it away here.
// Also, F0 is the *only* register we ever evaluate
// into, so we should only see register/register as F0/F0.
if(ismem(f) && ismem(t))
goto hard;
if(f->op == OREGISTER && t->op == OREGISTER) {
if(f->val.u.reg != D_F0 || t->val.u.reg != D_F0)
goto fatal;
return;
}
if(ismem(f) && ismem(t))
goto hard;
a = AFMOVF;
if(ft == TFLOAT64)
a = AFMOVD;
@ -1509,6 +1514,8 @@ gmove(Node *f, Node *t)
break;
case CASE(TFLOAT32, TFLOAT64):
if(ismem(f) && ismem(t))
goto hard;
if(f->op == OREGISTER && t->op == OREGISTER) {
if(f->val.u.reg != D_F0 || t->val.u.reg != D_F0)
goto fatal;
@ -1521,6 +1528,8 @@ gmove(Node *f, Node *t)
return;
case CASE(TFLOAT64, TFLOAT32):
if(ismem(f) && ismem(t))
goto hard;
if(f->op == OREGISTER && t->op == OREGISTER) {
tempname(&r1, types[TFLOAT32]);
gins(AFMOVFP, f, &r1);

View File

@ -79,6 +79,7 @@ char *runtimeimport =
"func \"\".uint64mod (? uint64, ? uint64) uint64\n"
"func \"\".float64toint64 (? float64) int64\n"
"func \"\".int64tofloat64 (? int64) float64\n"
"func \"\".complex128div (num complex128, den complex128) (quo complex128)\n"
"\n"
"$$\n";
char *unsafeimport =

View File

@ -4,10 +4,12 @@
#include "gg.h"
static void subnode(Node *nr, Node *ni, Node *nc);
static void negate(Node *n);
static void zero(Node *n);
static int isimag1i(Node*);
static void subnode(Node *nr, Node *ni, Node *nc);
static void zero(Node *n);
static void minus(Node *nl, Node *res);
void complexminus(Node*, Node*);
void complexadd(int op, Node*, Node*, Node*);
void complexmul(Node*, Node*, Node*);
#define CASE(a,b) (((a)<<16)|((b)<<0))
@ -15,16 +17,12 @@ static int isimag1i(Node*);
* generate:
* res = n;
* simplifies and calls gmove.
* perm is
* 0 (r,i) -> (r,i)
* 1 (r,i) -> (-i,r) *1i
* 2 (r,i) -> (i,-r) /1i
*/
void
complexmove(Node *f, Node *t, int perm)
complexmove(Node *f, Node *t)
{
int ft, tt;
Node n1, n2, n3, n4, nc;
Node n1, n2, n3, n4;
if(debug['g']) {
dump("\ncomplexmove-f", f);
@ -50,65 +48,27 @@ complexmove(Node *f, Node *t, int perm)
// make from addable
if(!f->addable) {
tempname(&n1, f->type);
complexmove(f, &n1, 0);
complexmove(f, &n1);
f = &n1;
}
subnode(&n1, &n2, f);
subnode(&n3, &n4, t);
// perform the permutations.
switch(perm) {
case 0: // r,i => r,i
gmove(&n1, &n3);
gmove(&n2, &n4);
break;
case 1: // r,i => -i,r
regalloc(&nc, n3.type, N);
gmove(&n2, &nc);
negate(&nc);
gmove(&n1, &n4);
gmove(&nc, &n3);
regfree(&nc);
break;
case 2: // r,i => i,-r
regalloc(&nc, n4.type, N);
gmove(&n1, &nc);
negate(&nc);
gmove(&n2, &n3);
gmove(&nc, &n4);
regfree(&nc);
break;
}
cgen(&n1, &n3);
cgen(&n2, &n4);
break;
// these are depricated
case CASE(TFLOAT32,TCOMPLEX64):
case CASE(TFLOAT32,TCOMPLEX128):
case CASE(TFLOAT64,TCOMPLEX64):
case CASE(TFLOAT64,TCOMPLEX128):
// float to complex goes to real part
regalloc(&n1, types[ft], N);
subnode(&n1, &n2, t);
cgen(f, &n1);
subnode(&n3, &n4, t);
// perform the permutations.
switch(perm) {
case 0: // no permutations
gmove(&n1, &n3);
zero(&n4);
break;
case 1:
gmove(&n1, &n4);
zero(&n3);
break;
case 2:
negate(&n1);
gmove(&n1, &n4);
zero(&n3);
break;
}
regfree(&n1);
zero(&n2);
break;
}
}
@ -118,40 +78,44 @@ complexop(Node *n, Node *res)
{
if(n != N && n->type != T)
if(iscomplex[n->type->etype]) {
goto yes;
goto maybe;
}
if(res != N && res->type != T)
if(iscomplex[res->type->etype]) {
goto yes;
goto maybe;
}
if(n->op == OREAL || n->op == OIMAG)
return 1;
goto yes;
return 0;
goto no;
yes:
maybe:
switch(n->op) {
case OCONV: // implemented ops
case OADD:
case OSUB:
case OMUL:
case ODIV:
case OMINUS:
case OCMPLX:
case OREAL:
case OIMAG:
return 1;
goto yes;
case ODOT: // sudoaddr
case ODOT:
case ODOTPTR:
case OINDEX:
case OIND:
case ONAME:
return 1;
goto yes;
}
no:
//dump("\ncomplex-no", n);
return 0;
yes:
//dump("\ncomplex-yes", n);
return 1;
}
void
@ -159,8 +123,7 @@ complexgen(Node *n, Node *res)
{
Node *nl, *nr;
Node tnl, tnr;
Node n1, n2, n3, n4, n5, n6;
Node ra, rb, rc, rd;
Node n1, n2;
int tl, tr;
if(debug['g']) {
@ -171,35 +134,18 @@ complexgen(Node *n, Node *res)
// pick off float/complex opcodes
switch(n->op) {
case OCMPLX:
tempname(&tnr, n->type);
tr = simsimtype(n->type);
tr = cplxsubtype(tr);
n1 = tnr;
n1.type = types[tr];
n2 = tnr;
n2.type = types[tr];
n2.xoffset += n2.type->width;
subnode(&n1, &n2, res);
cgen(n->left, &n1);
cgen(n->right, &n2);
cgen(&tnr, res);
return;
case OREAL:
n = n->left;
tr = simsimtype(n->type);
tr = cplxsubtype(tr);
subnode(&n1, &n2, n);
subnode(&n1, &n2, n->left);
cgen(&n1, res);
return;
case OIMAG:
n = n->left;
tr = simsimtype(n->type);
tr = cplxsubtype(tr);
subnode(&n1, &n2, n);
subnode(&n1, &n2, n->left);
cgen(&n2, res);
return;
}
@ -212,10 +158,10 @@ complexgen(Node *n, Node *res)
if(tl != tr) {
if(!n->addable) {
tempname(&n1, n->type);
complexmove(n, &n1, 0);
complexmove(n, &n1);
n = &n1;
}
complexmove(n, res, 0);
complexmove(n, res);
return;
}
@ -226,7 +172,7 @@ complexgen(Node *n, Node *res)
return;
}
if(n->addable) {
complexmove(n, res, 0);
complexmove(n, res);
return;
}
@ -241,7 +187,7 @@ complexgen(Node *n, Node *res)
case OIND:
case ONAME: // PHEAP or PPARAMREF var
igen(n, &n1, res);
complexmove(&n1, res, 0);
complexmove(&n1, res);
regfree(&n1);
return;
@ -249,7 +195,6 @@ complexgen(Node *n, Node *res)
case OADD:
case OSUB:
case OMUL:
case ODIV:
case OMINUS:
case OCMPLX:
case OREAL:
@ -287,132 +232,22 @@ complexgen(Node *n, Node *res)
break;
case OCONV:
complexmove(nl, res, 0);
complexmove(nl, res);
break;
case OMINUS:
subnode(&n1, &n2, nl);
subnode(&n5, &n6, res);
regalloc(&ra, n5.type, N);
gmove(&n1, &ra);
negate(&ra);
gmove(&ra, &n5);
regfree(&ra);
regalloc(&ra, n5.type, N);
gmove(&n2, &ra);
negate(&ra);
gmove(&ra, &n6);
regfree(&ra);
complexminus(nl, res);
break;
case OADD:
case OSUB:
subnode(&n1, &n2, nl);
subnode(&n3, &n4, nr);
subnode(&n5, &n6, res);
regalloc(&ra, n5.type, N);
gmove(&n1, &ra);
gins(optoas(n->op, n5.type), &n3, &ra);
gmove(&ra, &n5);
regfree(&ra);
regalloc(&ra, n6.type, N);
gmove(&n2, &ra);
gins(optoas(n->op, n6.type), &n4, &ra);
gmove(&ra, &n6);
regfree(&ra);
complexadd(n->op, nl, nr, res);
break;
case OMUL:
if(isimag1i(nr)) {
complexmove(nl, res, 1);
break;
}
if(isimag1i(nl)) {
complexmove(nr, res, 1);
break;
}
subnode(&n1, &n2, nl);
subnode(&n3, &n4, nr);
subnode(&n5, &n6, res);
regalloc(&ra, n5.type, N);
regalloc(&rb, n5.type, N);
regalloc(&rc, n6.type, N);
regalloc(&rd, n6.type, N);
gmove(&n1, &ra);
gmove(&n3, &rc);
gins(optoas(OMUL, n5.type), &rc, &ra); // ra = a*c
gmove(&n2, &rb);
gmove(&n4, &rd);
gins(optoas(OMUL, n5.type), &rd, &rb); // rb = b*d
gins(optoas(OSUB, n5.type), &rb, &ra); // ra = (a*c - b*d)
gins(optoas(OMUL, n5.type), &n2, &rc); // rc = b*c
gins(optoas(OMUL, n5.type), &n1, &rd); // rd = a*d
gins(optoas(OADD, n5.type), &rd, &rc); // rc = (b*c + a*d)
gmove(&ra, &n5);
gmove(&rc, &n6);
regfree(&ra);
regfree(&rb);
regfree(&rc);
regfree(&rd);
break;
case ODIV:
if(isimag1i(nr)) {
complexmove(nl, res, 2);
break;
}
subnode(&n1, &n2, nl);
subnode(&n3, &n4, nr);
subnode(&n5, &n6, res);
regalloc(&ra, n5.type, N);
regalloc(&rb, n5.type, N);
regalloc(&rc, n6.type, N);
regalloc(&rd, n6.type, N);
gmove(&n1, &ra);
gmove(&n3, &rc);
gins(optoas(OMUL, n5.type), &rc, &ra); // ra = a*c
gmove(&n2, &rb);
gmove(&n4, &rd);
gins(optoas(OMUL, n5.type), &rd, &rb); // rb = b*d
gins(optoas(OADD, n5.type), &rb, &ra); // ra = (a*c + b*d)
gins(optoas(OMUL, n5.type), &n2, &rc); // rc = b*c
gins(optoas(OMUL, n5.type), &n1, &rd); // rd = a*d
gins(optoas(OSUB, n5.type), &rd, &rc); // rc = (b*c - a*d)
gmove(&n3, &rb);
gins(optoas(OMUL, n5.type), &rb, &rb); // rb = c*c
gmove(&n4, &rd);
gins(optoas(OMUL, n5.type), &rd, &rd); // rd = d*d
gins(optoas(OADD, n5.type), &rd, &rb); // rb = (c*c + d*d)
gins(optoas(ODIV, n5.type), &rb, &ra); // ra = (a*c + b*d)/(c*c + d*d)
gins(optoas(ODIV, n5.type), &rb, &rc); // rc = (b*c - a*d)/(c*c + d*d)
gmove(&ra, &n5);
gmove(&rc, &n6);
regfree(&ra);
regfree(&rb);
regfree(&rc);
regfree(&rd);
complexmul(nl, nr, res);
break;
// ODIV call a runtime function
}
}
@ -487,18 +322,6 @@ nodfconst(Node *n, Type *t, Mpflt* fval)
fatal("nodfconst: bad type %T", t);
}
static int
isimag1i(Node *n)
{
if(n != N)
if(n->op == OLITERAL)
if(n->val.ctype == CTCPLX)
if(mpgetflt(&n->val.u.cval->real) == 0.0)
if(mpgetflt(&n->val.u.cval->imag) == 1.0)
return 1;
return 0;
}
// break addable nc-complex into nr-real and ni-imaginary
static void
subnode(Node *nr, Node *ni, Node *nc)
@ -527,25 +350,6 @@ subnode(Node *nr, Node *ni, Node *nc)
ni->xoffset += t->width;
}
// generate code to negate register nr
static void
negate(Node *nr)
{
Node nc;
Mpflt fval;
memset(&nc, 0, sizeof(nc));
nc.op = OLITERAL;
nc.addable = 1;
ullmancalc(&nc);
nc.val.u.fval = &fval;
nc.val.ctype = CTFLT;
nc.type = nr->type;
mpmovecflt(nc.val.u.fval, -1.0);
gins(optoas(OMUL, nr->type), &nc, nr);
}
// generate code to zero addable dest nr
static void
zero(Node *nr)
@ -563,5 +367,116 @@ zero(Node *nr)
mpmovecflt(nc.val.u.fval, 0.0);
gmove(&nc, nr);
cgen(&nc, nr);
}
// generate code res = -nl
static void
minus(Node *nl, Node *res)
{
Node ra;
memset(&ra, 0, sizeof(ra));
ra.op = OMINUS;
ra.left = nl;
ra.type = nl->type;
cgen(&ra, res);
}
// build and execute tree
// real(res) = -real(nl)
// imag(res) = -imag(nl)
void
complexminus(Node *nl, Node *res)
{
Node n1, n2, n5, n6;
subnode(&n1, &n2, nl);
subnode(&n5, &n6, res);
minus(&n1, &n5);
minus(&n2, &n6);
}
// build and execute tree
// real(res) = real(nl) op real(nr)
// imag(res) = imag(nl) op imag(nr)
void
complexadd(int op, Node *nl, Node *nr, Node *res)
{
Node n1, n2, n3, n4, n5, n6;
Node ra;
subnode(&n1, &n2, nl);
subnode(&n3, &n4, nr);
subnode(&n5, &n6, res);
memset(&ra, 0, sizeof(ra));
ra.op = op;
ra.left = &n1;
ra.right = &n3;
ra.type = n1.type;
cgen(&ra, &n5);
memset(&ra, 0, sizeof(ra));
ra.op = op;
ra.left = &n2;
ra.right = &n4;
ra.type = n2.type;
cgen(&ra, &n6);
}
// build and execute tree
// real(res) = real(nl)*real(nr) - imag(nl)*imag(nr)
// imag(res) = real(nl)*imag(nr) + imag(nl)*real(nr)
void
complexmul(Node *nl, Node *nr, Node *res)
{
Node n1, n2, n3, n4, n5, n6;
Node rm1, rm2, ra;
subnode(&n1, &n2, nl);
subnode(&n3, &n4, nr);
subnode(&n5, &n6, res);
// real part
memset(&rm1, 0, sizeof(ra));
rm1.op = OMUL;
rm1.left = &n1;
rm1.right = &n3;
rm1.type = n1.type;
memset(&rm2, 0, sizeof(ra));
rm2.op = OMUL;
rm2.left = &n2;
rm2.right = &n4;
rm2.type = n2.type;
memset(&ra, 0, sizeof(ra));
ra.op = OSUB;
ra.left = &rm1;
ra.right = &rm2;
ra.type = rm1.type;
cgen(&ra, &n5);
// imag part
memset(&rm1, 0, sizeof(ra));
rm1.op = OMUL;
rm1.left = &n1;
rm1.right = &n4;
rm1.type = n1.type;
memset(&rm2, 0, sizeof(ra));
rm2.op = OMUL;
rm2.left = &n2;
rm2.right = &n3;
rm2.type = n2.type;
memset(&ra, 0, sizeof(ra));
ra.op = OADD;
ra.left = &rm1;
ra.right = &rm2;
ra.type = rm1.type;
cgen(&ra, &n6);
}

View File

@ -101,3 +101,5 @@ func int64mod(int64, int64) int64
func uint64mod(uint64, uint64) uint64
func float64toint64(float64) int64
func int64tofloat64(int64) float64
func complex128div(num complex128, den complex128) (quo complex128)

View File

@ -851,13 +851,22 @@ walkexpr(Node **np, NodeList **init)
case ODIV:
case OMOD:
walkexpr(&n->left, init);
walkexpr(&n->right, init);
/*
* rewrite complex div into function call.
*/
et = n->left->type->etype;
if(iscomplex[et] && n->op == ODIV) {
n = mkcall("complex128div", n->type, init,
conv(n->left, types[TCOMPLEX128]),
conv(n->right, types[TCOMPLEX128]));
goto ret;
}
/*
* rewrite div and mod into function calls
* on 32-bit architectures.
*/
walkexpr(&n->left, init);
walkexpr(&n->right, init);
et = n->left->type->etype;
if(widthptr > 4 || (et != TUINT64 && et != TINT64))
goto ret;
if(et == TINT64)

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@ -48,6 +48,7 @@ OFILES=\
chan.$O\
closure.$O\
float.$O\
complex.$O\
hashmap.$O\
iface.$O\
malloc.$O\

36
src/pkg/runtime/complex.c Normal file
View File

@ -0,0 +1,36 @@
// 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.
#include "runtime.h"
// complex128div(num, den complex128) (quo complex128)
void
·complex128div(float64 numreal, float64 numimag,
float64 denreal, float64 denimag,
float64 quoreal, float64 quoimag)
{
float64 a, b, ratio, denom;
a = denreal;
if(a < 0)
a = -a;
b = denimag;
if(b < 0)
b = -b;
if(a <= b) {
if(b == 0)
throw("complex divide");
ratio = denreal/denimag;
denom = denreal*ratio + denimag;
quoreal = (numreal*ratio + numimag) / denom;
quoimag = (numimag*ratio - numreal) / denom;
} else {
ratio = denimag/denreal;
denom = denimag*ratio + denreal;
quoreal = (numimag*ratio + numreal) / denom;
quoimag = (numimag - numreal*ratio) / denom;
}
FLUSH(&quoreal);
FLUSH(&quoimag);
}

View File

@ -56,6 +56,25 @@ Hello World!
== ken/
=========== ken/cplx0.go
(+5.000000e+000+6.000000e+000i)
(+5.000000e+000+6.000000e+000i)
(+5.000000e+000+6.000000e+000i)
(+5.000000e+000+6.000000e+000i)
=========== ken/cplx3.go
(+1.292308e+000-1.384615e-001i)
(+1.292308e+000-1.384615e-001i)
64
=========== ken/cplx4.go
c = (-5.000000-6.000000i)
c = (5.000000+6.000000i)
c = (5.000000+6.000000i)
c = (5.000000+6.000000i)
c = (5+6i)
c = (13+7i)
=========== ken/intervar.go
print 1 bio 2 file 3 -- abc

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@ -1,6 +1,6 @@
// true
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// 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.

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@ -1,6 +1,6 @@
// [ $GOARCH != amd64 ] || ($G $D/$F.go && $L $F.$A && ./$A.out)
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// 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.

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@ -1,6 +1,6 @@
// [ $GOARCH != amd64 ] || ($G $D/$F.go && $L $F.$A && ./$A.out)
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// 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.

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@ -1,6 +1,6 @@
// true
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// 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.
@ -20,7 +20,7 @@ var complexBits = reflect.Typeof(complex(0i)).Size() * 8
func main() {
c0 := C1
c0 = (c0+c0+c0) / (c0+c0)
c0 = (c0+c0+c0) / (c0+c0+3i)
println(c0)
c := *(*complex)(unsafe.Pointer(&c0))

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@ -1,6 +1,6 @@
// true
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// 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.