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Commit e978955d by David Malcolm
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analyzer: fix ICE in __builtin_isnan (PR 93356) 

PR analyzer/93356 reports an ICE handling __builtin_isnan due to a
failing assertion:
  674     gcc_assert (lhs_ec_id != rhs_ec_id);
with op=UNORDERED_EXPR.
when attempting to add an UNORDERED_EXPR constraint.

This is an overzealous assertion, but underlying it are various forms of
sloppiness regarding NaN within the analyzer:

  (a) the assumption in the constraint_manager that equivalence classes
  are reflexive (X == X), which isn't the case for NaN.

  (b) Hardcoding the "honor_nans" param to false when calling
  invert_tree_comparison throughout the analyzer.

  (c) Ignoring ORDERED_EXPR, UNORDERED_EXPR, and the UN-prefixed
  comparison codes.

I wrote a patch for this which tracks the NaN-ness of floating-point
values and uses this to address all of the above.

However, to minimize changes in gcc 10 stage 4, here's a simpler patch
which rejects attempts to query or add constraints on floating-point
values, instead treating any floating-point comparison as "unknown", and
silently dropping the constraints at edges.

gcc/analyzer/ChangeLog:
	PR analyzer/93356
	* region-model.cc (region_model::eval_condition): In both
	overloads, bail out immediately on floating-point types.
	(region_model::eval_condition_without_cm): Likewise.
	(region_model::add_constraint): Likewise.

gcc/testsuite/ChangeLog:
	PR analyzer/93356
	* gcc.dg/analyzer/conditionals-notrans.c (test_float_selfcmp):
	Add.
	* gcc.dg/analyzer/conditionals-trans.c: Mark floating point
	comparison test as failing.
	(test_float_selfcmp): Add.
	* gcc.dg/analyzer/data-model-1.c: Mark floating point comparison
	tests as failing.
	* gcc.dg/analyzer/torture/pr93356.c: New test.

gcc/ChangeLog:
	PR analyzer/93356
	* doc/analyzer.texi (Limitations): Note that constraints on
	floating-point values are currently ignored.
parent f9eb0973
Showing with 80 additions and 5 deletions
gcc/ChangeLog
2020-01-30 David Malcolm <dmalcolm@redhat.com>
PR analyzer/93356
* doc/analyzer.texi (Limitations): Note that constraints on
floating-point values are currently ignored.
2020-01-30 Jakub Jelinek <jakub@redhat.com>
PR lto/93384
......
gcc/analyzer/ChangeLog
2020-01-30 David Malcolm <dmalcolm@redhat.com>
PR analyzer/93356
* region-model.cc (region_model::eval_condition): In both
overloads, bail out immediately on floating-point types.
(region_model::eval_condition_without_cm): Likewise.
(region_model::add_constraint): Likewise.
2020-01-30 David Malcolm <dmalcolm@redhat.com>
PR analyzer/93450
* program-state.cc (sm_state_map::set_state): For the overload
taking an svalue_id, bail out if the set_state on the ec does
......
gcc/analyzer/region-model.cc
......@@ -5144,6 +5144,15 @@ region_model::eval_condition (svalue_id lhs_sid,
enum tree_code op,
svalue_id rhs_sid) const
{
svalue *lhs = get_svalue (lhs_sid);
svalue *rhs = get_svalue (rhs_sid);
/* For now, make no attempt to capture constraints on floating-point
values. */
if ((lhs->get_type () && FLOAT_TYPE_P (lhs->get_type ()))
|| (rhs->get_type () && FLOAT_TYPE_P (rhs->get_type ())))
return tristate::unknown ();
tristate ts = eval_condition_without_cm (lhs_sid, op, rhs_sid);
if (ts.is_known ())
......@@ -5173,6 +5182,12 @@ region_model::eval_condition_without_cm (svalue_id lhs_sid,
/* See what we know based on the values. */
if (lhs && rhs)
{
/* For now, make no attempt to capture constraints on floating-point
values. */
if ((lhs->get_type () && FLOAT_TYPE_P (lhs->get_type ()))
|| (rhs->get_type () && FLOAT_TYPE_P (rhs->get_type ())))
return tristate::unknown ();
if (lhs == rhs)
{
/* If we have the same svalue, then we have equality
......@@ -5252,6 +5267,11 @@ bool
region_model::add_constraint (tree lhs, enum tree_code op, tree rhs,
region_model_context *ctxt)
{
/* For now, make no attempt to capture constraints on floating-point
values. */
if (FLOAT_TYPE_P (TREE_TYPE (lhs)) || FLOAT_TYPE_P (TREE_TYPE (rhs)))
return true;
svalue_id lhs_sid = get_rvalue (lhs, ctxt);
svalue_id rhs_sid = get_rvalue (rhs, ctxt);
......@@ -5385,6 +5405,11 @@ region_model::eval_condition (tree lhs,
tree rhs,
region_model_context *ctxt)
{
/* For now, make no attempt to model constraints on floating-point
values. */
if (FLOAT_TYPE_P (TREE_TYPE (lhs)) || FLOAT_TYPE_P (TREE_TYPE (rhs)))
return tristate::unknown ();
return eval_condition (get_rvalue (lhs, ctxt), op, get_rvalue (rhs, ctxt));
}
......
gcc/doc/analyzer.texi
......@@ -390,6 +390,8 @@ Lack of function pointer analysis
@item
The constraint-handling code assumes reflexivity in some places
(that values are equal to themselves), which is not the case for NaN.
As a simple workaround, constraints on floating-point values are
currently ignored.
@item
The region model code creates lots of little mutable objects at each
@code{region_model} (and thus per @code{exploded_node}) rather than
......
gcc/testsuite/ChangeLog
2020-01-30 Jeff Law <law@redhat.com
2020-01-30 David Malcolm <dmalcolm@redhat.com>
PR analyzer/93356
* gcc.dg/analyzer/conditionals-notrans.c (test_float_selfcmp):
Add.
* gcc.dg/analyzer/conditionals-trans.c: Mark floating point
comparison test as failing.
(test_float_selfcmp): Add.
* gcc.dg/analyzer/data-model-1.c: Mark floating point comparison
tests as failing.
* gcc.dg/analyzer/torture/pr93356.c: New test.
2020-01-30 Jeff Law <law@redhat.com>
PR c/88660
* gcc.dg/pr88660.c: New test
......
gcc/testsuite/gcc.dg/analyzer/conditionals-notrans.c
......@@ -157,3 +157,9 @@ void test_range_float_ge_le (float f)
__analyzer_eval (f == 4); /* { dg-warning "TRUE" "desired" { xfail *-*-* } } */
/* { dg-bogus "UNKNOWN" "status quo" { xfail *-*-* } .-1 } */
}
void test_float_selfcmp (float f)
{
__analyzer_eval (f == f); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (f != f); /* { dg-warning "UNKNOWN" } */
}
gcc/testsuite/gcc.dg/analyzer/conditionals-trans.c
......@@ -140,5 +140,12 @@ void test_range_float_ge_le (float f)
{
if (f >= 4)
if (f <= 4)
__analyzer_eval (f == 4); /* { dg-warning "TRUE" } */
__analyzer_eval (f == 4); /* { dg-warning "TRUE" "PR 93356" { xfail *-*-* } } */
/* { dg-warning "UNKNOWN" "disabled float comparisons" { target *-*-* } .-1 } */
}
void test_float_selfcmp (float f)
{
__analyzer_eval (f == f); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (f != f); /* { dg-warning "UNKNOWN" } */
}
gcc/testsuite/gcc.dg/analyzer/data-model-1.c
......@@ -209,14 +209,16 @@ void test_13 (struct outer *o)
{
__analyzer_eval (o->mid.in.f == 0.f); /* { dg-warning "UNKNOWN" } */
o->mid.in.f = 0.f;
__analyzer_eval (o->mid.in.f == 0.f); /* { dg-warning "TRUE" } */
__analyzer_eval (o->mid.in.f == 0.f); /* { dg-warning "TRUE" "PR 93356" { xfail *-*-* } } */
/* { dg-warning "UNKNOWN" "disabled float comparisons" { target *-*-* } .-1 } */
}
void test_14 (struct outer o)
{
__analyzer_eval (o.mid.in.f == 0.f); /* { dg-warning "UNKNOWN" } */
o.mid.in.f = 0.f;
__analyzer_eval (o.mid.in.f == 0.f); /* { dg-warning "TRUE" } */
__analyzer_eval (o.mid.in.f == 0.f); /* { dg-warning "TRUE" "PR 93356" { xfail *-*-* } } */
/* { dg-warning "UNKNOWN" "disabled float comparisons" { target *-*-* } .-1 } */
}
void test_15 (const char *str)
......@@ -947,7 +949,8 @@ void test_42 (void)
float f;
i = 42;
f = i;
__analyzer_eval (f == 42.0); /* { dg-warning "TRUE" } */
__analyzer_eval (f == 42.0); /* { dg-warning "TRUE" "PR 93356" { xfail *-*-* } } */
/* { dg-warning "UNKNOWN" "disabled float comparisons" { target *-*-* } .-1 } */
}
void test_43 (void)
......
gcc/testsuite/gcc.dg/analyzer/torture/pr93356.c 0 → 100644
void
test (double d)
{
if (__builtin_isnan (d))
return;
}
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