[gcc r11-4864] Normalize VARYING for -fstrict-enums.
Aldy Hernandez
aldyh@gcc.gnu.org
Tue Nov 10 08:29:07 GMT 2020
https://gcc.gnu.org/g:3d3470e239e8040f642a8852721b4962b4ed36f2
commit r11-4864-g3d3470e239e8040f642a8852721b4962b4ed36f2
Author: Aldy Hernandez <aldyh@redhat.com>
Date: Mon Nov 9 20:35:25 2020 +0100
Normalize VARYING for -fstrict-enums.
The problem here is that the representation for VARYING in
-fstrict-enums is different between value_range and irange.
The helper function irange::normalize_min_max() will normalize to
VARYING only if setting the range to the entire domain of the
underlying type. That is, [0, 0xff..ff], not the domain as defined by
-fstrict-enums. This causes problems because the multi-range version
of varying_p() will return true if the range is the domain as defined
by -fstrict-enums. Thus, normalize_min_max and varying_p have
different concepts of varying for multi-ranges.
(BTW, legacy ranges are different because they never look at the
extremes of a range to determine varying-ness. They only look at the
kind field.)
One approach is to change all the code to limit ranges to the domain
in the -fstrict-enums world, but this won't work because there are
various instances of gimple where the values assigned or compared are
beyond the limits of TYPE_{MIN,MAX}_VALUE. One example is the
addition of 0xffffffff to represent subtraction.
This patch fixes multi-range varying_p() and set_varying() to agree
with the normalization code, using the extremes of the underlying type,
to represent varying.
gcc/ChangeLog:
PR tree-optimization/97767
* value-range.cc (dump_bound_with_infinite_markers): Use
wi::min_value and wi::max_value.
(range_tests_strict_enum): New.
(range_tests): Call range_tests_strict_enum.
* value-range.h (irange::varying_p): Use wi::min_value
and wi::max_value.
(irange::set_varying): Same.
(irange::normalize_min_max): Remove comment.
gcc/testsuite/ChangeLog:
* g++.dg/opt/pr97767.C: New test.
Diff:
---
gcc/testsuite/g++.dg/opt/pr97767.C | 10 +++++++++
gcc/value-range.cc | 42 ++++++++++++++++++++++++++++++++++++--
gcc/value-range.h | 23 +++++++++------------
3 files changed, 60 insertions(+), 15 deletions(-)
diff --git a/gcc/testsuite/g++.dg/opt/pr97767.C b/gcc/testsuite/g++.dg/opt/pr97767.C
new file mode 100644
index 00000000000..da0879d0567
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr97767.C
@@ -0,0 +1,10 @@
+// { dg-do compile }
+// { dg-options "-O -fstrict-enums -ftree-vrp -w" }
+
+enum { E0 = 0, E1 = 1, E2 = 2 } e;
+
+int
+foo (void)
+{
+ return __builtin_popcount ((int) e);
+}
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index 61f7da278d6..f83a824a982 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -1866,12 +1866,17 @@ static void
dump_bound_with_infinite_markers (FILE *file, tree bound)
{
tree type = TREE_TYPE (bound);
+ wide_int type_min = wi::min_value (TYPE_PRECISION (type), TYPE_SIGN (type));
+ wide_int type_max = wi::max_value (TYPE_PRECISION (type), TYPE_SIGN (type));
+
if (INTEGRAL_TYPE_P (type)
&& !TYPE_UNSIGNED (type)
- && vrp_val_is_min (bound)
+ && TREE_CODE (bound) == INTEGER_CST
+ && wi::to_wide (bound) == type_min
&& TYPE_PRECISION (type) != 1)
fprintf (file, "-INF");
- else if (vrp_val_is_max (bound)
+ else if (TREE_CODE (bound) == INTEGER_CST
+ && wi::to_wide (bound) == type_max
&& TYPE_PRECISION (type) != 1)
fprintf (file, "+INF");
else
@@ -2241,6 +2246,38 @@ range_tests_legacy ()
}
}
+// Simulate -fstrict-enums where the domain of a type is less than the
+// underlying type.
+
+static void
+range_tests_strict_enum ()
+{
+ // The enum can only hold [0, 3].
+ tree rtype = copy_node (unsigned_type_node);
+ TYPE_MIN_VALUE (rtype) = build_int_cstu (rtype, 0);
+ TYPE_MAX_VALUE (rtype) = build_int_cstu (rtype, 3);
+
+ // Test that even though vr1 covers the strict enum domain ([0, 3]),
+ // it does not cover the domain of the underlying type.
+ int_range<1> vr1 (build_int_cstu (rtype, 0), build_int_cstu (rtype, 1));
+ int_range<1> vr2 (build_int_cstu (rtype, 2), build_int_cstu (rtype, 3));
+ vr1.union_ (vr2);
+ ASSERT_TRUE (vr1 == int_range<1> (build_int_cstu (rtype, 0),
+ build_int_cstu (rtype, 3)));
+ ASSERT_FALSE (vr1.varying_p ());
+
+ // Test that copying to a multi-range does not change things.
+ int_range<2> ir1 (vr1);
+ ASSERT_TRUE (ir1 == vr1);
+ ASSERT_FALSE (ir1.varying_p ());
+
+ // The same test as above, but using TYPE_{MIN,MAX}_VALUE instead of [0,3].
+ vr1 = int_range<1> (TYPE_MIN_VALUE (rtype), TYPE_MAX_VALUE (rtype));
+ ir1 = vr1;
+ ASSERT_TRUE (ir1 == vr1);
+ ASSERT_FALSE (ir1.varying_p ());
+}
+
static void
range_tests_misc ()
{
@@ -2442,6 +2479,7 @@ range_tests ()
range_tests_legacy ();
range_tests_irange3 ();
range_tests_int_range_max ();
+ range_tests_strict_enum ();
range_tests_misc ();
}
diff --git a/gcc/value-range.h b/gcc/value-range.h
index a483fc802dd..7428c91ea57 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -280,12 +280,14 @@ irange::varying_p () const
tree l = m_base[0];
tree u = m_base[1];
tree t = TREE_TYPE (l);
+ unsigned prec = TYPE_PRECISION (t);
+ signop sign = TYPE_SIGN (t);
if (INTEGRAL_TYPE_P (t))
- return l == TYPE_MIN_VALUE (t) && u == TYPE_MAX_VALUE (t);
+ return (wi::to_wide (l) == wi::min_value (prec, sign)
+ && wi::to_wide (u) == wi::max_value (prec, sign));
if (POINTER_TYPE_P (t))
- return wi::to_wide (l) == 0
- && wi::to_wide (u) == wi::max_value (TYPE_PRECISION (t),
- TYPE_SIGN (t));
+ return (wi::to_wide (l) == 0
+ && wi::to_wide (u) == wi::max_value (prec, sign));
return true;
}
@@ -469,8 +471,10 @@ irange::set_varying (tree type)
m_num_ranges = 1;
if (INTEGRAL_TYPE_P (type))
{
- m_base[0] = TYPE_MIN_VALUE (type);
- m_base[1] = TYPE_MAX_VALUE (type);
+ wide_int min = wi::min_value (TYPE_PRECISION (type), TYPE_SIGN (type));
+ wide_int max = wi::max_value (TYPE_PRECISION (type), TYPE_SIGN (type));
+ m_base[0] = wide_int_to_tree (type, min);
+ m_base[1] = wide_int_to_tree (type, max);
}
else if (POINTER_TYPE_P (type))
{
@@ -566,13 +570,6 @@ irange::set_zero (tree type)
}
// Normalize a range to VARYING or UNDEFINED if possible.
-//
-// Avoid using TYPE_{MIN,MAX}_VALUE because -fstrict-enums can
-// restrict those to a subset of what actually fits in the type.
-// Instead use the extremes of the type precision which will allow
-// compare_range_with_value() to check if a value is inside a range,
-// whereas if we used TYPE_*_VAL, said function would just punt upon
-// seeing a VARYING.
inline void
irange::normalize_min_max ()
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