As Jakub mentioned in the PR, because many numbers have multiple
possible representations, we can't reliably return true here.
I'll commit this if tests pass.
I wonder if its worth even handling decimal floats in frange, since
there's a lot of things we can't represent. I suppose even though we
could never propagate an actual value with VRP, we could fold
conditionals (symbolic and stuff outside ranges, etc) ??.
Thoughts?
PR middle-end/106831
gcc/ChangeLog:
* value-range.cc (frange::singleton_p): Return false for
DECIMAL_FLOAT_TYPE_P.
---
gcc/value-range.cc | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index c3f668a811a..12a3750d078 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -647,6 +647,14 @@ frange::singleton_p (tree *result) const
if (HONOR_NANS (m_type) && !get_nan ().no_p ())
return false;
+ // Because the significand is not normalized (there is no
+ // implicit leading "1"). Most values with less than 7
+ // significant digits have multiple possible representations.
+ // Zero has 192 possible representations (or twice that for
+ // signed zeros).
+ if (DECIMAL_FLOAT_TYPE_P (m_type))
+ return false;
+
// Return the appropriate zero if known.
if (HONOR_SIGNED_ZEROS (m_type) && zero_p ())
{
--
2.37.1
