On 21/07/2014 14:23, Roman Gareev wrote:
I've attached the patch, which contains generation of Gimple code from
isl_ast_node_block.
However, I've found out a problem. The following example:
int k = 50;
static int __attribute__((noinline))
foo ()
{
int i, res;
for (i = 0, res = 0; i < k; i++)
res += i;
return res;
}
extern void abort ();
int
main (void)
{
int res = foo ();
if (res != 1225)
abort ();
return 0;
}.
produces the following code, which executes without error:
ISL AST generated by ISL:
{
for (int c1 = 0; c1 < k.0; c1 += 1)
S_4(c1);
S_6();
}
Gimple code:
loop_0 (header = 0, latch = 1, niter = )
{
bb_2 (preds = {bb_0 }, succs = {bb_3 bb_8 })
{
<bb 2>:
# VUSE <.MEM_3(D)>
k.0_9 = k;
if (k.0_9 > 0)
goto <bb 3>;
else
goto <bb 8>;
}
bb_3 (preds = {bb_2 }, succs = {bb_4 bb_7 })
{
<bb 3>:
# .MEM_8 = VDEF <.MEM_3(D)>
phi_out_of_ssa.5[0] = 0;
_20 = k.0_9 > 0;
if (_20 != 0)
goto <bb 4>;
else
goto <bb 7>;
}
bb_4 (preds = {bb_3 }, succs = {bb_5 })
{
<bb 4>:
_21 = (signed long) k.0_9;
_22 = _21 + -1;
}
bb_7 (preds = {bb_5 bb_3 }, succs = {bb_8 })
{
<bb 7>:
# .MEM_30 = PHI <.MEM_29(5), .MEM_8(3)>
# VUSE <.MEM_30>
res_32 = Close_Phi.6[0];
# .MEM_33 = VDEF <.MEM_30>
Cross_BB_scalar_dependence.7[0] = res_32;
# VUSE <.MEM_33>
res_17 = Cross_BB_scalar_dependence.7[0];
_16 = res_17;
}
bb_8 (preds = {bb_7 bb_2 }, succs = {bb_1 })
{
<bb 8>:
# res_12 = PHI <_16(7), 0(2)>
# .MEM_2 = PHI <.MEM_33(7), .MEM_3(D)(2)>
# VUSE <.MEM_2>
return res_12;
}
loop_2 (header = 5, latch = 6, niter = (unsigned long) ((signed
long) k.0_9 + -1), upper_bound = 9223372036854775806)
{
bb_5 (preds = {bb_4 bb_6 }, succs = {bb_6 bb_7 })
{
<bb 5>:
# graphite_IV.8_23 = PHI <0(4), graphite_IV.8_24(6)>
# .MEM_31 = PHI <.MEM_8(4), .MEM_29(6)>
# VUSE <.MEM_31>
res_25 = phi_out_of_ssa.5[0];
_27 = (int) graphite_IV.8_23;
res_26 = res_25 + _27;
# .MEM_28 = VDEF <.MEM_31>
Close_Phi.6[0] = res_26;
# .MEM_29 = VDEF <.MEM_28>
phi_out_of_ssa.5[0] = res_26;
graphite_IV.8_24 = graphite_IV.8_23 + 1;
if (graphite_IV.8_23 < _22)
goto <bb 6>;
else
goto <bb 7>;
}
bb_6 (preds = {bb_5 }, succs = {bb_5 })
{
<bb 6>:
goto <bb 5>;
}
}
}
It is similar to the original code:
loop_0 (header = 0, latch = 1, niter = )
{
bb_2 (preds = {bb_0 }, succs = {bb_3 bb_8 })
{
<bb 2>:
# VUSE <.MEM_3(D)>
k.0_9 = k;
if (k.0_9 > 0)
goto <bb 3>;
else
goto <bb 8>;
}
bb_3 (preds = {bb_2 }, succs = {bb_5 })
{
<bb 3>:
# .MEM_8 = VDEF <.MEM_3(D)>
phi_out_of_ssa.5[0] = 0;
goto <bb 5>;
}
bb_4 (preds = {bb_7 }, succs = {bb_8 })
{
<bb 4>:
# .MEM_19 = PHI <.MEM_18(7)>
# VUSE <.MEM_19>
res_17 = Cross_BB_scalar_dependence.7[0];
_16 = res_17;
goto <bb 8>;
}
bb_7 (preds = {bb_5 }, succs = {bb_4 })
{
<bb 7>:
# VUSE <.MEM_13>
res_4 = Close_Phi.6[0];
# .MEM_18 = VDEF <.MEM_13>
Cross_BB_scalar_dependence.7[0] = res_4;
goto <bb 4>;
}
bb_8 (preds = {bb_4 bb_2 }, succs = {bb_1 })
{
<bb 8>:
# res_12 = PHI <_16(4), 0(2)>
# .MEM_2 = PHI <.MEM_19(4), .MEM_3(D)(2)>
# VUSE <.MEM_2>
return res_12;
}
loop_1 (header = 5, latch = 6, niter = , upper_bound = 2147483646)
{
bb_5 (preds = {bb_3 bb_6 }, succs = {bb_6 bb_7 })
{
<bb 5>:
# i_10 = PHI <0(3), i_6(6)>
# .MEM_1 = PHI <.MEM_8(3), .MEM_13(6)>
# VUSE <.MEM_1>
res_11 = phi_out_of_ssa.5[0];
res_5 = res_11 + i_10;
# .MEM_7 = VDEF <.MEM_1>
Close_Phi.6[0] = res_5;
# .MEM_13 = VDEF <.MEM_7>
phi_out_of_ssa.5[0] = res_5;
i_6 = i_10 + 1;
if (i_6 < k.0_9)
goto <bb 6>;
else
goto <bb 7>;
}
bb_6 (preds = {bb_5 }, succs = {bb_5 })
{
<bb 6>:
goto <bb 5>;
}
}
}
If we change the name of variable k to n:
int n = 50;
static int __attribute__((noinline))
foo ()
{
int i, res;
for (i = 0, res = 0; i < n; i++)
res += i;
return res;
}
extern void abort ();
int
main (void)
{
int res = foo ();
if (res != 1225)
abort ();
return 0;
}
the following code will be produced, which gives wrong result
ISL AST generated by ISL:
{
S_6();
for (int c1 = 0; c1 < n.0; c1 += 1)
S_4(c1);
}
It seems S_6 is now scheduled before S_4 which is surprising, as
dependences from S_4 to S_6 should prevent us from generating a schedule
that yields such a result. What is the schedule that you give to the isl
ast generator?
Cheers,
Tobias
P.S.: The patch looks good by itself, but needs some test cases. As you
have them in this email, we can just add them after we understood this bug.
