new file mode 100644
@@ -0,0 +1,15 @@
+// { dg-do compile }
+// { dg-options "-O2" }
+
+int a, b, c;
+static int d(long e, long f) { return f == 0 || e && f == 1 ?: f; }
+int g(void) {static int t; return t;}
+static void h(long e) {
+ b = e - 1;
+ a = d(b || d(e, 8), g());
+}
+int tt;
+void i(void) {
+ c = (__SIZE_TYPE__)&tt;
+ h(c);
+}
@@ -1876,6 +1876,8 @@ irange::get_bitmask () const
//
// 3 is in the range endpoints, but is excluded per the known 0 bits
// in the mask.
+ //
+ // See also the note in irange_bitmask::intersect.
irange_bitmask bm = get_bitmask_from_range ();
if (!m_bitmask.unknown_p ())
bm.intersect (m_bitmask);
@@ -1915,10 +1917,18 @@ irange::intersect_bitmask (const irange &r)
return false;
irange_bitmask bm = get_bitmask ();
+ irange_bitmask save = bm;
if (!bm.intersect (r.get_bitmask ()))
return false;
m_bitmask = bm;
+
+ // Updating m_bitmask may still yield a semantic bitmask (as
+ // returned by get_bitmask) which is functionally equivalent to what
+ // we originally had. In which case, there's still no change.
+ if (save == get_bitmask ())
+ return false;
+
if (!set_range_from_bitmask ())
normalize_kind ();
if (flag_checking)
@@ -1938,10 +1948,18 @@ irange::union_bitmask (const irange &r)
return false;
irange_bitmask bm = get_bitmask ();
+ irange_bitmask save = bm;
if (!bm.union_ (r.get_bitmask ()))
return false;
m_bitmask = bm;
+
+ // Updating m_bitmask may still yield a semantic bitmask (as
+ // returned by get_bitmask) which is functionally equivalent to what
+ // we originally had. In which case, there's still no change.
+ if (save == get_bitmask ())
+ return false;
+
// No need to call set_range_from_mask, because we'll never
// narrow the range. Besides, it would cause endless recursion
// because of the union_ in set_range_from_mask.
The mask/value pair we track in the irange is a bit fickle in that it can sometimes contradict the bitmask inherent in the range. This can happen when a series of calculations yield a combination such as: [3, 1000] MASK 0xfffffffe VALUE 0x0 The mask/value above implies that the lowest bit is a known 0, which would exclude the 3 in the range. At one time we tried keeping mask and ranges 100% consistent, but the performance penalty was too high (5% in VRP). Also, it's unclear whether the intersection of two incompatible known bits should make the whole range undefined, or just the contradicting bits. This is all documented in irange::get_bitmask(). We could revisit both of these assumptions in the future. In this testcase IPA ends up with a range where the lower 2 bits are expected to be 0, but the range is [1,1]. [irange] long int [1, 1] MASK 0xfffffffffffffffc VALUE 0x0 This causes irange::union_bitmask() to think an update occurred, when no semantic change happened, thus triggering an assert in IPA-cp. We could get rid of the assert, but it's cleaner to make irange::{union,intersect}_bitmask always tell the truth. Beside, the ranger's cache also depends on union being truthful. PR ipa/110753 gcc/ChangeLog: * value-range.cc (irange::union_bitmask): Return FALSE if updated bitmask is semantically equivalent to the original mask. (irange::intersect_bitmask): Same. (irange::get_bitmask): Add comment. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr110753.c: New test. --- gcc/testsuite/gcc.dg/tree-ssa/pr110753.c | 15 +++++++++++++++ gcc/value-range.cc | 18 ++++++++++++++++++ 2 files changed, 33 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr110753.c