Richard Biener <richard.guent...@gmail.com> writes:
>>> Looking at the implementation it seems it would also work with
>>>
>>> return MIN (TREE_INT_CST_EXT_NUNITS (m_t), N / HOST_BITS_PER_WIDE_INT);
>>
>> Yeah, the MIN in the patch was probably bogus sorry. It only works
>> if we can assume that no bitsizetype will have ADDR_MAX_PRECISION
>> significant (non-sign) bits -- in particular that there's no such thing as
>> an all-1s _unsigned_ bitsizetype. That might be true in practice given
>> the way we use offsets, but it isn't safe to generalise that to all N.
>>
>> A safer form would be:
>>
>> if (ext_len > OFFSET_INT_ELTS)
>> TREE_INT_CST_OFFSET_NUNITS (t) = len;
>> else
>> TREE_INT_CST_OFFSET_NUNITS (t) = ext_len;
>>
>> The reason the general form doesn't work for all N is because of the
>> compressed representation. E.g. the example I gave a while ago about
>> a 256-bit all-1s unsigned number being { -1 } as a 256-bit number and
>> { -1, -1, -1, -1, 0 } as a 257+-bit number.
>>
>> But the point of the patch is to avoid any runtime checks here,
>> so the TYPE_PRECISION case is never actually used now. I just kept
>> it around for completeness, since we'd been using it successfully so far.
>> I can put in a gcc_unreachable if you prefer.
>
> Yeah, I'd prefer a gcc_unreachable and a comment.
OK, how about this version? Tested on x86_64-linux-gnu.
Thanks,
Richard
Index: gcc/ChangeLog.wide-int
===================================================================
--- gcc/ChangeLog.wide-int 2013-12-03 23:55:26.142873345 +0000
+++ gcc/ChangeLog.wide-int 2013-12-03 23:59:18.823744425 +0000
@@ -617,6 +617,7 @@
(TREE_INT_CST_HIGH): Delete.
(TREE_INT_CST_NUNITS): New.
(TREE_INT_CST_EXT_NUNITS): Likewise.
+ (TREE_INT_CST_OFFSET_NUNITS): Likewise.
(TREE_INT_CST_ELT): Likewise.
(INT_CST_LT): Use wide-int interfaces.
(INT_CST_LE): New.
Index: gcc/tree-core.h
===================================================================
--- gcc/tree-core.h 2013-12-03 23:55:26.142873345 +0000
+++ gcc/tree-core.h 2013-12-04 00:02:22.910222722 +0000
@@ -764,11 +764,17 @@ struct GTY(()) tree_base {
struct {
/* The number of HOST_WIDE_INTs if the INTEGER_CST is accessed in
its native precision. */
- unsigned short unextended;
+ unsigned char unextended;
/* The number of HOST_WIDE_INTs if the INTEGER_CST is extended to
wider precisions based on its TYPE_SIGN. */
- unsigned short extended;
+ unsigned char extended;
+
+ /* The number of HOST_WIDE_INTs if the INTEGER_CST is accessed in
+ offset_int precision, with smaller integers being extended
+ according to their TYPE_SIGN. This is equal to one of the two
+ fields above but is cached for speed. */
+ unsigned char offset;
} int_length;
/* VEC length. This field is only used with TREE_VEC. */
Index: gcc/tree.c
===================================================================
--- gcc/tree.c 2013-12-03 23:55:26.142873345 +0000
+++ gcc/tree.c 2013-12-03 23:59:18.821744409 +0000
@@ -1285,6 +1285,7 @@ wide_int_to_tree (tree type, const wide_
/* Make sure no one is clobbering the shared constant. */
gcc_checking_assert (TREE_TYPE (t) == type
&& TREE_INT_CST_NUNITS (t) == 1
+ && TREE_INT_CST_OFFSET_NUNITS (t) == 1
&& TREE_INT_CST_EXT_NUNITS (t) == 1
&& TREE_INT_CST_ELT (t, 0) == hwi);
else
@@ -1964,6 +1965,13 @@ make_int_cst_stat (int len, int ext_len
TREE_SET_CODE (t, INTEGER_CST);
TREE_INT_CST_NUNITS (t) = len;
TREE_INT_CST_EXT_NUNITS (t) = ext_len;
+ /* to_offset can only be applied to trees that are offset_int-sized
+ or smaller. EXT_LEN is correct if it fits, otherwise the constant
+ must be exactly the precision of offset_int and so LEN is correct. */
+ if (ext_len <= OFFSET_INT_ELTS)
+ TREE_INT_CST_OFFSET_NUNITS (t) = ext_len;
+ else
+ TREE_INT_CST_OFFSET_NUNITS (t) = len;
TREE_CONSTANT (t) = 1;
Index: gcc/tree.h
===================================================================
--- gcc/tree.h 2013-12-03 23:55:26.142873345 +0000
+++ gcc/tree.h 2013-12-04 00:01:48.258944485 +0000
@@ -907,6 +907,8 @@ #define TREE_INT_CST_NUNITS(NODE) \
(INTEGER_CST_CHECK (NODE)->base.u.int_length.unextended)
#define TREE_INT_CST_EXT_NUNITS(NODE) \
(INTEGER_CST_CHECK (NODE)->base.u.int_length.extended)
+#define TREE_INT_CST_OFFSET_NUNITS(NODE) \
+ (INTEGER_CST_CHECK (NODE)->base.u.int_length.offset)
#define TREE_INT_CST_ELT(NODE, I) TREE_INT_CST_ELT_CHECK (NODE, I)
#define TREE_INT_CST_LOW(NODE) \
((unsigned HOST_WIDE_INT) TREE_INT_CST_ELT (NODE, 0))
@@ -4623,11 +4625,15 @@ wi::extended_tree <N>::get_val () const
inline unsigned int
wi::extended_tree <N>::get_len () const
{
- if (N == MAX_BITSIZE_MODE_ANY_INT
- || N > TYPE_PRECISION (TREE_TYPE (m_t)))
+ if (N == ADDR_MAX_PRECISION)
+ return TREE_INT_CST_OFFSET_NUNITS (m_t);
+ else if (N == MAX_BITSIZE_MODE_ANY_INT)
return TREE_INT_CST_EXT_NUNITS (m_t);
else
- return TREE_INT_CST_NUNITS (m_t);
+ /* This class is designed to be used for specific output precisions
+ and needs to be as fast as possible, so there is no fallback for
+ other casees. */
+ gcc_unreachable ();
}
namespace wi
Index: gcc/wide-int.h
===================================================================
--- gcc/wide-int.h 2013-12-03 23:59:08.135658583 +0000
+++ gcc/wide-int.h 2013-12-03 23:59:18.823744425 +0000
@@ -256,6 +256,9 @@ #define ADDR_MAX_BITSIZE 64
#define ADDR_MAX_PRECISION \
((ADDR_MAX_BITSIZE + 4 + HOST_BITS_PER_WIDE_INT - 1) &
~(HOST_BITS_PER_WIDE_INT - 1))
+/* The number of HWIs needed to store an offset_int. */
+#define OFFSET_INT_ELTS (ADDR_MAX_PRECISION / HOST_BITS_PER_WIDE_INT)
+
/* The type of result produced by a binary operation on types T1 and T2.
Defined purely for brevity. */
#define WI_BINARY_RESULT(T1, T2) \
