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x86_64: Fix indirection in struct paramaters 

The first loop setting up struct arguments must not remove
elements from the vstack (via vtop--), as gen_reg needs them to
potentially evict some argument still held in registers to stack.

Swapping the arg in question to top (and back to its place) also
simplifies the vstore call itself, as not funny save/restore
or some "non-existing" stack elements need to be done.

Generally for a stack a vop-- operation conceptually clobbers
that element, so further references to it aren't allowed anymore.
master
Michael Matz 2012-04-15 05:12:43 +02:00
parent 5c0a2366a3
commit 86ac6b9bee
2 changed files with 41 additions and 29 deletions
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29
tests/tcctest.c
View File

@ -1122,25 +1122,30 @@ struct structa1 struct_assign_test2(struct structa1 s1, int t)
void struct_assign_test(void)
{
struct structa1 lsta1, lsta2;
struct S {
struct structa1 lsta1, lsta2;
int i;
} s, *ps;
ps = &s;
ps->i = 4;
#if 0
printf("struct_assign_test:\n");
lsta1.f1 = 1;
lsta1.f2 = 2;
printf("%d %d\n", lsta1.f1, lsta1.f2);
lsta2 = lsta1;
printf("%d %d\n", lsta2.f1, lsta2.f2);
s.lsta1.f1 = 1;
s.lsta1.f2 = 2;
printf("%d %d\n", s.lsta1.f1, s.lsta1.f2);
s.lsta2 = s.lsta1;
printf("%d %d\n", s.lsta2.f1, s.lsta2.f2);
#else
lsta2.f1 = 1;
lsta2.f2 = 2;
s.lsta2.f1 = 1;
s.lsta2.f2 = 2;
#endif
struct_assign_test1(lsta2, 3, 4.5);
struct_assign_test1(ps->lsta2, 3, 4.5);
printf("before call: %d %d\n", lsta2.f1, lsta2.f2);
lsta2 = struct_assign_test2(lsta2, 4);
printf("after call: %d %d\n", lsta2.f1, lsta2.f2);
printf("before call: %d %d\n", s.lsta2.f1, s.lsta2.f2);
ps->lsta2 = struct_assign_test2(ps->lsta2, ps->i);
printf("after call: %d %d\n", ps->lsta2.f1, ps->lsta2.f2);
static struct {
void (*elem)();

41
x86_64-gen.c
View File

@ -820,7 +820,6 @@ static const uint8_t arg_regs[REGN] = {
void gfunc_call(int nb_args)
{
int size, align, r, args_size, i;
SValue *orig_vtop;
int nb_reg_args = 0;
int nb_sse_args = 0;
int sse_reg, gen_reg;
@ -845,7 +844,6 @@ void gfunc_call(int nb_args)
/* for struct arguments, we need to call memcpy and the function
call breaks register passing arguments we are preparing.
So, we process arguments which will be passed by stack first. */
orig_vtop = vtop;
gen_reg = nb_reg_args;
sse_reg = nb_sse_args;
@ -861,6 +859,14 @@ void gfunc_call(int nb_args)
}
for(i = 0; i < nb_args; i++) {
/* Swap argument to top, it will possibly be changed here,
and might use more temps. All arguments must remain on the
stack, so that get_reg can correctly evict some of them onto
stack. We could use also use a vrott(nb_args) at the end
of this loop, but this seems faster. */
SValue tmp = vtop[0];
vtop[0] = vtop[-i];
vtop[-i] = tmp;
if ((vtop->type.t & VT_BTYPE) == VT_STRUCT) {
size = type_size(&vtop->type, &align);
/* align to stack align size */
@ -872,18 +878,9 @@ void gfunc_call(int nb_args)
r = get_reg(RC_INT);
orex(1, r, 0, 0x89); /* mov %rsp, r */
o(0xe0 + REG_VALUE(r));
{
/* following code breaks vtop[1], vtop[2], and vtop[3] */
SValue tmp1 = vtop[1];
SValue tmp2 = vtop[2];
SValue tmp3 = vtop[3];
vset(&vtop->type, r | VT_LVAL, 0);
vswap();
vstore();
vtop[1] = tmp1;
vtop[2] = tmp2;
vtop[3] = tmp3;
}
vset(&vtop->type, r | VT_LVAL, 0);
vswap();
vstore();
args_size += size;
} else if ((vtop->type.t & VT_BTYPE) == VT_LDOUBLE) {
gv(RC_ST0);
@ -913,10 +910,14 @@ void gfunc_call(int nb_args)
args_size += 8;
}
}
vtop--;
}
vtop = orig_vtop;
/* And swap the argument back to it's original position. */
tmp = vtop[0];
vtop[0] = vtop[-i];
vtop[-i] = tmp;
}
/* XXX This should be superfluous. */
save_regs(0); /* save used temporary registers */
/* then, we prepare register passing arguments.
@ -953,6 +954,12 @@ void gfunc_call(int nb_args)
vtop--;
}
/* We shouldn't have many operands on the stack anymore, but the
call address itself is still there, and it might be in %eax
(or edx/ecx) currently, which the below writes would clobber.
So evict all remaining operands here. */
save_regs(0);
/* Copy R10 and R11 into RDX and RCX, respectively */
if (nb_reg_args > 2) {
o(0xd2894c); /* mov %r10, %rdx */