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re PR tree-optimization/87147 (GCC miscompiles at -O3 on valid code)

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2018-08-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87147
	* tree-ssa-sccvn.c (SSA_VISITED): New function.
	(visit_phi): When the degenerate result is from the backedge and
	we didn't visit its definition yet drop to VARYING.
	(do_rpo_vn): Properly mark blocks with incoming backedges as executable.

	* gcc.dg/torture/pr87147.c: New testcase.

From-SVN: r263980
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Richard Biener 2018-08-30 12:37:10 +00:00 • committed by Richard Biener
parent 28428506aa
commit b1d5f64492
4 changed files with 67 additions and 7 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2018-08-30 Richard Biener <rguenther@suse.de>
PR tree-optimization/87147
* tree-ssa-sccvn.c (SSA_VISITED): New function.
(visit_phi): When the degenerate result is from the backedge and
we didn't visit its definition yet drop to VARYING.
(do_rpo_vn): Properly mark blocks with incoming backedges as executable.
2018-08-29 Jan Hubicka <jh@suse.cz>
* lto-streamer-out.c (DFS::DFS_write_tree_body): Do not walk

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2018-08-30 Richard Biener <rguenther@suse.de>
PR tree-optimization/87147
* gcc.dg/torture/pr87147.c: New testcase.
2018-08-30 Tamar Christina <tamar.christina@arm.com>
* gcc.target/aarch64/large_struct_copy_2.c: New.

22
gcc/testsuite/gcc.dg/torture/pr87147.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-do run } */
short a;
long b;
int c, d, g;
char e, h;
long f[] = {0};
int main()
{
int i = 1;
for (; a <= 3; a++) {
c = 0;
for (; c <= 2; c++) {
b = 0;
for (; b <= 3; b++) {
h = i && f[d];
e = g && i;
i = 0;
}
}
}
}

39
gcc/tree-ssa-sccvn.c
View file

@ -462,6 +462,15 @@ SSA_VAL (tree x)
return tem && tem->visited ? tem->valnum : x;
}
/* Return whether X was visited. */
inline bool
SSA_VISITED (tree x)
{
vn_ssa_aux_t tem = vn_ssa_aux_hash->find_with_hash (x, SSA_NAME_VERSION (x));
return tem && tem->visited;
}
/* Return the SSA value of the VUSE x, supporting released VDEFs
during elimination which will value-number the VDEF to the
associated VUSE (but not substitute in the whole lattice). */
@ -4100,6 +4109,7 @@ static bool
visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
{
tree result, sameval = VN_TOP, seen_undef = NULL_TREE;
tree backedge_name = NULL_TREE;
tree sameval_base = NULL_TREE;
poly_int64 soff, doff;
unsigned n_executable = 0;
@ -4126,9 +4136,13 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
tree def = PHI_ARG_DEF_FROM_EDGE (phi, e);
++n_executable;
if (TREE_CODE (def) == SSA_NAME
&& (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK)))
def = SSA_VAL (def);
if (TREE_CODE (def) == SSA_NAME)
{
if (e->flags & EDGE_DFS_BACK)
backedge_name = def;
if (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK))
def = SSA_VAL (def);
}
if (def == VN_TOP)
;
/* Ignore undefined defs for sameval but record one. */
@ -4162,10 +4176,15 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
}
}
/* If the value we want to use is the backedge and that wasn't visited
yet drop to VARYING. */
if (backedge_name
&& sameval == backedge_name
&& !SSA_VISITED (backedge_name))
result = PHI_RESULT (phi);
/* If none of the edges was executable keep the value-number at VN_TOP,
if only a single edge is exectuable use its value. */
if (n_executable <= 1)
else if (n_executable <= 1)
result = seen_undef ? seen_undef : sameval;
/* If we saw only undefined values and VN_TOP use one of the
undefined values. */
@ -6298,6 +6317,7 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
{
basic_block bb = BASIC_BLOCK_FOR_FN (fn, rpo[i]);
rpo_state[i].visited = 0;
bb->flags &= ~BB_EXECUTABLE;
bool has_backedges = false;
edge e;
edge_iterator ei;
@ -6306,12 +6326,17 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
if (e->flags & EDGE_DFS_BACK)
has_backedges = true;
if (! iterate && (e->flags & EDGE_DFS_BACK))
e->flags |= EDGE_EXECUTABLE;
{
e->flags |= EDGE_EXECUTABLE;
/* ??? Strictly speaking we only need to unconditionally
process a block when it is in an irreducible region,
thus when it may be reachable via the backedge only. */
bb->flags |= BB_EXECUTABLE;
}
else
e->flags &= ~EDGE_EXECUTABLE;
}
rpo_state[i].iterate = iterate && has_backedges;
bb->flags &= ~BB_EXECUTABLE;
}
entry->flags |= EDGE_EXECUTABLE;
entry->dest->flags |= BB_EXECUTABLE;