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Fix inchash handling of wide_ints (PR91242)

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inchash:#️⃣:add_wide_int operated directly on the raw encoding
of the wide_int, including any redundant upper bits.  The problem
with that is that the upper bits are only defined for some wide-int
storage types (including wide_int itself).  wi::to_wide(tree) instead
returns a value that is extended according to the signedness of the
type (so that wi::to_widest can use the same encoding) while rtxes
have the awkward special case of BI, which can be zero-extended
rather than sign-extended.

In the PR, we computed a hash for a "normal" sign-extended wide_int
while the existing entries hashed wi::to_wide(tree).  This gives
different results for unsigned types that have the top bit set.

The patch fixes that by hashing the canonical sign-extended form even
if the raw encoding happens to be different.

2019-07-29  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* wide-int.h (generic_wide_int::sext_elt): New function.
	* inchash.h (hash::add_wide_int): Use it instead of elt.

From-SVN: r273881
This commit is contained in:
Richard Sandiford 2019-07-29 18:50:25 +00:00 • committed by Richard Sandiford
parent 5c6aa9a891
commit 5d5bb9bc26
3 changed files with 24 additions and 1 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2019-07-29 Richard Sandiford <richard.sandiford@arm.com>
* wide-int.h (generic_wide_int::sext_elt): New function.
* inchash.h (hash::add_wide_int): Use it instead of elt.
2019-07-29 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* config/arm/arm-builtins.c (acle_builtin_data): Expand VAR1 to

2
gcc/inchash.h
View file

@ -85,7 +85,7 @@ class hash
{
add_int (x.get_len ());
for (unsigned i = 0; i < x.get_len (); i++)
add_hwi (x.elt (i));
add_hwi (x.sext_elt (i));
}
/* Hash in pointer PTR. */

18
gcc/wide-int.h
View file

@ -730,6 +730,7 @@ public:
/* Public accessors for the interior of a wide int. */
HOST_WIDE_INT sign_mask () const;
HOST_WIDE_INT elt (unsigned int) const;
HOST_WIDE_INT sext_elt (unsigned int) const;
unsigned HOST_WIDE_INT ulow () const;
unsigned HOST_WIDE_INT uhigh () const;
HOST_WIDE_INT slow () const;
@ -909,6 +910,23 @@ generic_wide_int <storage>::elt (unsigned int i) const
return this->get_val ()[i];
}
/* Like elt, but sign-extend beyond the upper bit, instead of returning
the raw encoding. */
template <typename storage>
inline HOST_WIDE_INT
generic_wide_int <storage>::sext_elt (unsigned int i) const
{
HOST_WIDE_INT elt_i = elt (i);
if (!is_sign_extended)
{
unsigned int precision = this->get_precision ();
unsigned int lsb = i * HOST_BITS_PER_WIDE_INT;
if (precision - lsb < HOST_BITS_PER_WIDE_INT)
elt_i = sext_hwi (elt_i, precision - lsb);
}
return elt_i;
}
template <typename storage>
template <typename T>
inline generic_wide_int <storage> &