[COMMITTED] irange: keep better track of powers of 2.
Commit Message
When setting the nonzero bits to a mask containing only one bit, set
the range immediately, as it can be devined from the mask. This helps
us keep better track of powers of two.
For example, with this patch a nonzero mask of 0x8000 is set to a
range of [0,0][0x8000,0x8000] with a nonzero mask of 0x8000.
Tested on x86-64 Linux.
p.s. Thanks for the bug report Uli.
gcc/ChangeLog:
* value-range.cc (irange::set_nonzero_bits): Set range when known.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/popcount6.c: New test.
---
gcc/testsuite/gcc.dg/tree-ssa/popcount6.c | 12 ++++++++++++
gcc/value-range.cc | 13 +++++++++++++
2 files changed, 25 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/popcount6.c
new file mode 100644
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp" }
+
+int g(int n)
+{
+ n &= 0x8000;
+ if (n == 0)
+ return 1;
+ return __builtin_popcount(n);
+}
+
+// { dg-final { scan-tree-dump "return 1;" "evrp" } }
@@ -2930,6 +2930,19 @@ irange::set_nonzero_bits (const wide_int_ref &bits)
set_nonzero_bits (NULL);
return;
}
+ // If we have only one bit set in the mask, we can figure out the
+ // range immediately.
+ if (wi::popcount (bits) == 1)
+ {
+ bool has_zero = contains_p (build_zero_cst (type ()));
+ set (type (), bits, bits);
+ if (has_zero)
+ {
+ int_range<2> zero;
+ zero.set_zero (type ());
+ union_ (zero);
+ }
+ }
set_nonzero_bits (wide_int_to_tree (type (), bits));
}