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6g: simplify trampoline by postponing load.

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TEXT tramp
		MOVQ 8(SP), AX
		ADDQ $40, AX
		MOVQ AX, 8(SP)
		JMP oldfunc

	is now

	TEXT tramp
		ADDQ $40, 8(SP)
		JMP oldfunc

	and if s/40/0/, then it simplifies to

	TEXT tramp
		JMP oldfunc

	(the tramp is still needed to satisfy
	symbol references from other object files)

R=ken
OCL=28377
CL=28381
This commit is contained in:
Russ Cox 2009-05-06 17:06:06 -07:00
parent e508c55760
commit 5a67ea3883
1 changed files with 37 additions and 22 deletions
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59
src/cmd/6g/obj.c
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@ -272,7 +272,7 @@ data(void)
{
gflag = debug['g'];
debug['g'] = 0;
if(estrdat == nil) {
strdat = mal(sizeof(*pc));
clearp(strdat);
@ -324,7 +324,7 @@ datastring(char *s, int len, Addr *a)
Strlit lit;
char buf[100];
} tmp;
// string
memset(&ao, 0, sizeof(ao));
ao.type = D_STATIC;
@ -421,7 +421,7 @@ datagostring(Strlit *sval, Addr *a)
wi = types[TUINT32]->width;
wp = types[tptr]->width;
if(ap.index == D_STATIC) {
// huge strings are made static to avoid long names
snprint(namebuf, sizeof(namebuf), ".gostring.%d", ++gen);
@ -457,7 +457,7 @@ datagostring(Strlit *sval, Addr *a)
p->from.scale = wi;
p->to = ac;
p->to.offset = sval->len;
p = pc;
ggloblsym(ao.sym, types[TSTRING]->width, ao.type == D_EXTERN);
if(ao.type == D_STATIC)
@ -553,7 +553,7 @@ void
genembedtramp(Type *t, Sig *b)
{
Sym *e;
int c, d, o;
int c, d, o, loaded;
Prog *p;
Type *f;
@ -566,9 +566,6 @@ genembedtramp(Type *t, Sig *b)
fatal("genembedtramp %T.%s", t, b->name);
out:
if(d == 0)
return;
// print("genembedtramp %d\n", d);
// print(" t = %lT\n", t);
// print(" name = %s\n", b->name);
@ -587,20 +584,24 @@ out:
p->from.scale = 7;
//print("1. %P\n", p);
//MOVQ 8(SP), AX
p = pc;
gins(AMOVQ, N, N);
p->from.type = D_INDIR+D_SP;
p->from.offset = 8;
p->to.type = D_AX;
//print("2. %P\n", p);
loaded = 0;
o = 0;
for(c=d-1; c>=0; c--) {
f = dotlist[c].field;
o += f->width;
if(!isptr[f->type->etype])
continue;
if(!loaded) {
loaded = 1;
//MOVQ 8(SP), AX
p = pc;
gins(AMOVQ, N, N);
p->from.type = D_INDIR+D_SP;
p->from.offset = 8;
p->to.type = D_AX;
//print("2. %P\n", p);
}
//MOVQ o(AX), AX
p = pc;
gins(AMOVQ, N, N);
@ -616,17 +617,31 @@ out:
gins(AADDQ, N, N);
p->from.type = D_CONST;
p->from.offset = o;
p->to.type = D_AX;
if(loaded)
p->to.type = D_AX;
else {
p->to.type = D_INDIR+D_SP;
p->to.offset = 8;
}
//print("4. %P\n", p);
}
//MOVQ AX, 8(SP)
p = pc;
gins(AMOVQ, N, N);
p->from.type = D_AX;
p->to.type = D_INDIR+D_SP;
p->to.offset = 8;
if(loaded) {
p = pc;
gins(AMOVQ, N, N);
p->from.type = D_AX;
p->to.type = D_INDIR+D_SP;
p->to.offset = 8;
//print("5. %P\n", p);
} else {
// TODO(rsc): obviously this is unnecessary,
// but 6l has a bug, and it can't handle
// JMP instructions too close to the top of
// a new function.
p = pc;
gins(ANOP, N, N);
}
f = dotlist[0].field;
//JMP main·*Sub_test2(SB)