| Message ID | 20241109013502.2642495-1-quic_apinski@quicinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | VN: Don't recurse on for the same value of `a | b` [PR117496] | expand |
> Am 09.11.2024 um 02:36 schrieb Andrew Pinski <quic_apinski@quicinc.com>: > > After adding vn_valueize to the handle the `a | b ==/!= 0` case > of insert_predicates_for_cond, it would go into an infinite loop > as the Value number for either a or b could be the same as what it > is for the whole expression. This avoids that recursion so there is > no infinite loop here. > > Bootstrapped and tested on x86_64-linux. Ok Richard > PR tree-optimization/117496 > > gcc/ChangeLog: > > * tree-ssa-sccvn.cc (insert_predicates_for_cond): If the > valueization for the new lhs is the same as the old one, > don't recurse. > > gcc/testsuite/ChangeLog: > > * gcc.dg/torture/pr117496-1.c: New test. > > Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com> > --- > gcc/testsuite/gcc.dg/torture/pr117496-1.c | 25 +++++++++++++++++++++++ > gcc/tree-ssa-sccvn.cc | 11 ++++++++-- > 2 files changed, 34 insertions(+), 2 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/torture/pr117496-1.c > > diff --git a/gcc/testsuite/gcc.dg/torture/pr117496-1.c b/gcc/testsuite/gcc.dg/torture/pr117496-1.c > new file mode 100644 > index 00000000000..f35d13dfa85 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/torture/pr117496-1.c > @@ -0,0 +1,25 @@ > +/* { dg-do compile } */ > + > + > +/* PR tree-optimization/117496 */ > +/* This would go into an infinite loop into VN while recording > + the predicates for the `tracks == 0 && wm == 0` GIMPLE_COND. > + As wm_N and tracks_N would valueize back to `tracks | wm`. */ > + > +int main_argc, gargs_preemp, gargs_nopreemp; > +static void gargs(); > +void main_argv() { > + int tracks = 0; > + gargs(main_argc, main_argv, &tracks); > +} > +void gargs(int, char *, int *tracksp) { > + int tracks = *tracksp, wm; > + for (;;) { > + if (tracks == 0) > + wm |= 4; > + if (gargs_nopreemp) > + gargs_preemp = 0; > + if (tracks == 0 && wm == 0) > + tracks++; > + } > +} > diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc > index 16299662b95..e93acb44200 100644 > --- a/gcc/tree-ssa-sccvn.cc > +++ b/gcc/tree-ssa-sccvn.cc > @@ -7900,6 +7900,7 @@ insert_related_predicates_on_edge (enum tree_code code, tree *ops, edge pred_e) > > /* Insert on the TRUE_E true and FALSE_E false predicates > derived from LHS CODE RHS. */ > + > static void > insert_predicates_for_cond (tree_code code, tree lhs, tree rhs, > edge true_e, edge false_e) > @@ -7977,10 +7978,16 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs, > tree nlhs; > > nlhs = vn_valueize (gimple_assign_rhs1 (def_stmt)); > - insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); > + /* A valueization of the `a` might return the old lhs > + which is already handled above. */ > + if (nlhs != lhs) > + insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); > > + /* A valueization of the `b` might return the old lhs > + which is already handled above. */ > nlhs = vn_valueize (gimple_assign_rhs2 (def_stmt)); > - insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); > + if (nlhs != lhs) > + insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); > } > } > } > -- > 2.43.0 >
diff --git a/gcc/testsuite/gcc.dg/torture/pr117496-1.c b/gcc/testsuite/gcc.dg/torture/pr117496-1.c new file mode 100644 index 00000000000..f35d13dfa85 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr117496-1.c @@ -0,0 +1,25 @@ +/* { dg-do compile } */ + + +/* PR tree-optimization/117496 */ +/* This would go into an infinite loop into VN while recording + the predicates for the `tracks == 0 && wm == 0` GIMPLE_COND. + As wm_N and tracks_N would valueize back to `tracks | wm`. */ + +int main_argc, gargs_preemp, gargs_nopreemp; +static void gargs(); +void main_argv() { + int tracks = 0; + gargs(main_argc, main_argv, &tracks); +} +void gargs(int, char *, int *tracksp) { + int tracks = *tracksp, wm; + for (;;) { + if (tracks == 0) + wm |= 4; + if (gargs_nopreemp) + gargs_preemp = 0; + if (tracks == 0 && wm == 0) + tracks++; + } +} diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc index 16299662b95..e93acb44200 100644 --- a/gcc/tree-ssa-sccvn.cc +++ b/gcc/tree-ssa-sccvn.cc @@ -7900,6 +7900,7 @@ insert_related_predicates_on_edge (enum tree_code code, tree *ops, edge pred_e) /* Insert on the TRUE_E true and FALSE_E false predicates derived from LHS CODE RHS. */ + static void insert_predicates_for_cond (tree_code code, tree lhs, tree rhs, edge true_e, edge false_e) @@ -7977,10 +7978,16 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs, tree nlhs; nlhs = vn_valueize (gimple_assign_rhs1 (def_stmt)); - insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); + /* A valueization of the `a` might return the old lhs + which is already handled above. */ + if (nlhs != lhs) + insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); + /* A valueization of the `b` might return the old lhs + which is already handled above. */ nlhs = vn_valueize (gimple_assign_rhs2 (def_stmt)); - insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); + if (nlhs != lhs) + insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr); } } }
After adding vn_valueize to the handle the `a | b ==/!= 0` case of insert_predicates_for_cond, it would go into an infinite loop as the Value number for either a or b could be the same as what it is for the whole expression. This avoids that recursion so there is no infinite loop here. Bootstrapped and tested on x86_64-linux. PR tree-optimization/117496 gcc/ChangeLog: * tree-ssa-sccvn.cc (insert_predicates_for_cond): If the valueization for the new lhs is the same as the old one, don't recurse. gcc/testsuite/ChangeLog: * gcc.dg/torture/pr117496-1.c: New test. Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com> --- gcc/testsuite/gcc.dg/torture/pr117496-1.c | 25 +++++++++++++++++++++++ gcc/tree-ssa-sccvn.cc | 11 ++++++++-- 2 files changed, 34 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr117496-1.c