Hi,
this patch fixes graphite PR69067, a 6/7 regression.
I.
Consider the following test-case, compiled with -O1 -floop-nest-optimize
-flto:
...
int a1, c1, cr, kt;
int aa[2];
int
ce (void)
{
while (a1 < 1) {
int g8;
for (g8 = 0; g8 < 3; ++g8)
if (c1 != 0)
cr = aa[a1 * 2] = kt;
for (c1 = 0; c1 < 2; ++c1)
aa[c1] = cr;
++a1;
}
return 0;
}
int
main (void)
{
return ce (aa);
}
...
At graphite0, there's a loop with header bb4, which conditionally
executes bb 5:
...
<bb 3>:
<bb 4>:
# g8_39 = PHI <0(13), g8_19(3)>
# cr_lsm.1_4 = PHI <cr_lsm.1_21(13), cr_lsm.1_33(3)>
# cr_lsm.2_22 = PHI <cr_lsm.2_23(13), cr_lsm.2_11(3)>
if (c1_lsm.3_35 != 0)
goto <bb 5>;
else
goto <bb 6>;
<bb 5>:
aa[_3] = 0;
<bb 6>:
# cr_lsm.1_33 = PHI <cr_lsm.1_4(4), 0(5)>
# cr_lsm.2_11 = PHI <cr_lsm.2_22(4), 1(5)>
g8_19 = g8_39 + 1;
if (g8_19 <= 2)
goto <bb 3>;
else
goto <bb 7>;
...
II.
The graphite transformation moves the condition '(P_35 <= -1 || P_35 >=
1)' out of the loop:
...
[scheduler] original ast:
{
for (int c0 = 0; c0 <= 2; c0 += 1) {
S_4(c0);
if (P_35 <= -1 || P_35 >= 1)
S_5(c0);
S_6(c0);
}
S_7();
for (int c0 = 0; c0 <= 1; c0 += 1)
S_8(c0);
}
[scheduler] AST generated by isl:
{
if (P_35 <= -1) {
for (int c0 = 0; c0 <= 2; c0 += 1)
S_5(c0);
} else if (P_35 >= 1)
for (int c0 = 0; c0 <= 2; c0 += 1)
S_5(c0);
for (int c0 = 0; c0 <= 2; c0 += 1) {
S_4(c0);
S_6(c0);
}
S_7();
for (int c0 = 0; c0 <= 1; c0 += 1)
S_8(c0);
}
...
When instantiating the ast back to gimple, we run into an assert:
...
pr-graphite-4.c: In function ‘ce’:
pr-graphite-4.c:5:1: internal compiler error: in get_def_bb_for_const,
at graphite-isl-ast-to-gimple.c:1795
ce()
^
...
III.
What happens is the following: in copy_cond_phi_args we try to copy the
arguments of phi in bb6 to the arguments of new_phi in bb 46
...
(gdb) call debug_gimple_stmt (phi)
cr_lsm.1_33 = PHI <cr_lsm.1_4(4), 0(5)>
(gdb) call debug_gimple_stmt (new_phi)
cr_lsm.1_62 = PHI <(28), (47)>
...
While handling the '0' phi argument in add_phi_arg_for_new_expr we
trigger this bit of code and call get_def_bb_for_const with bb.index ==
46 and old_bb.index == 5:
...
/* If the corresponding def_bb could not be found the entry will
be NULL. */
if (TREE_CODE (old_phi_args[i]) == INTEGER_CST)
def_pred[i]
= get_def_bb_for_const (new_bb,
gimple_phi_arg_edge (phi, i)->src);
...
Neither of the two copies of bb 5 dominates bb 46, so we run into the
assert at the end:
...
/* Returns a basic block that could correspond to where a constant was
defined in the original code. In the original code OLD_BB had the
definition, we need to find which basic block out of the copies of
old_bb, in the new region, should a definition correspond to if it
has to reach BB. */
basic_block translate_isl_ast_to_gimple::
get_def_bb_for_const (basic_block bb, basic_block old_bb) const
{
vec <basic_block> *bbs = region->copied_bb_map->get (old_bb);
if (!bbs || bbs->is_empty ())
return NULL;
if (1 == bbs->length ())
return (*bbs)[0];
int i;
basic_block b1 = NULL, b2;
FOR_EACH_VEC_ELT (*bbs, i, b2)
{
if (b2 == bb)
return bb;
/* BB and B2 are in two unrelated if-clauses. */
if (!dominated_by_p (CDI_DOMINATORS, bb, b2))
continue;
/* Compute the nearest dominator. */
if (!b1 || dominated_by_p (CDI_DOMINATORS, b2, b1))
b1 = b2;
}
gcc_assert (b1);
return b1;
}
...
IV.
Attached patch fixes this by removing the assert.
Bootstrapped and reg-tested on x86_64.
OK for trunk, 6-branch?
Thanks,
- Tom
Remove assert in get_def_bb_for_const
2016-05-29 Tom de Vries <t...@codesourcery.com>
PR tree-optimization/69067
* graphite-isl-ast-to-gimple.c (get_def_bb_for_const): Remove assert.
* gcc.dg/graphite/pr69067.c: New test.
---
gcc/graphite-isl-ast-to-gimple.c | 1 -
gcc/testsuite/gcc.dg/graphite/pr69067.c | 28 ++++++++++++++++++++++++++++
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/gcc/graphite-isl-ast-to-gimple.c b/gcc/graphite-isl-ast-to-gimple.c
index 049a4c5..ff1d91f 100644
--- a/gcc/graphite-isl-ast-to-gimple.c
+++ b/gcc/graphite-isl-ast-to-gimple.c
@@ -1792,7 +1792,6 @@ get_def_bb_for_const (basic_block bb, basic_block old_bb) const
b1 = b2;
}
- gcc_assert (b1);
return b1;
}
diff --git a/gcc/testsuite/gcc.dg/graphite/pr69067.c b/gcc/testsuite/gcc.dg/graphite/pr69067.c
new file mode 100644
index 0000000..d767381d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/graphite/pr69067.c
@@ -0,0 +1,28 @@
+/* { dg-do link } */
+/* { dg-options " -O1 -floop-nest-optimize" } */
+/* { dg-additional-options "-flto" { target lto } } */
+
+int a1, c1, cr, kt;
+int aa[2];
+
+int
+ce (void)
+{
+ while (a1 < 1)
+ {
+ int g8;
+ for (g8 = 0; g8 < 3; ++g8)
+ if (c1 != 0)
+ cr = aa[a1 * 2] = kt;
+ for (c1 = 0; c1 < 2; ++c1)
+ aa[c1] = cr;
+ ++a1;
+ }
+ return 0;
+}
+
+int
+main (void)
+{
+ return ce (aa);
+}
