Kenneth Zadeck <zad...@naturalbridge.com> writes:
>> Or do you want to optimize encoding like for CONST_INT (and unlike
>> CONST_DOUBLE)? I doubt the above packs nicely into rtx_def?
>> A general issue of it though - we waste 32bits on 64bit hosts in
>> rtx_def between the bits and the union. Perfect place for num_elem
>> (if you really need it) and avoids another 4 byte hole. Similar issue
>> exists in rtvec_def.
> I am going to let richard answer this.
I agree this would be nice, but (stating the obvious) only on targets
where there is a hole. I suppose that translates to something like:
#if (HOST_BITS_PER_PTR > HOST_BITS_PER_INT \
|| HOST_BITS_PER_WIDE_INT > HOST_BITS_PER_INT)
#define RTL_LAYOUT 1
#else
#define RTL_LAYOUT 2
#endif
where HOST_BITS_PER_PTR would have to be set by a new configure-time test.
RTL_LAYOUT == 1 would put the CONST_WIDE_INT vector length in rtx_def itself,
probably as part of a new union, while RTL_LAYOUT == 2 would keep
it in its current place.
E.g. between:
unsigned return_val : 1;
and:
/* The first element of the operands of this rtx.
The number of operands and their types are controlled
by the `code' field, according to rtl.def. */
union u {
have:
#if RTL_LAYOUT == 1
union {
int num_elem;
} u2;
#endif
And:
struct GTY((variable_size)) hwivec_def {
#if RTL_LAYOUT == 2
int num_elem;
#endif
HOST_WIDE_INT elem[1];
};
>> +#if TARGET_SUPPORTS_WIDE_INT
>> +
>> +/* Match CONST_*s that can represent compile-time constant integers. */
>> +#define CASE_CONST_SCALAR_INT \
>> + case CONST_INT: \
>> + case CONST_WIDE_INT
>> +
>>
>> I regard this abstraction is mostly because the transition is not finished.
>> Not sure if seeing CASE_CONST_SCALAR_INT, CASE_CONST_UNIQUE (?),
>> CASE_CONST_ANY adds more to the confusion than spelling out all of them.
>> Isn't there sth like a tree-code-class for RTXen? That would catch
>> CASE_CONST_ANY, no?
Not as things stand. All constants are classified as RTX_CONST_OBJ,
which includes run-time constants like SYMBOL_REF as well. Whether it
makes sense to change the classification is really a separate question
from this patch. Besides, the other cases in the affected switch
statements aren't necessarily going to divide into classes either,
so we might still need CASE_CONST_ANY.
I'd like to keep these macros even after the conversion. They make
it more obvious what property is being tested, instead of having various
subsets of the CONST_* codes included by name. Reviewing the patch that
introduced the macros showed up instances where the existing switch
statements were wrong.
>> @@ -3081,6 +3081,8 @@ commutative_operand_precedence (rtx op)
>> /* Constants always come the second operand. Prefer "nice" constants.
>> */
>> if (code == CONST_INT)
>> return -8;
>> + if (code == CONST_WIDE_INT)
>> + return -8;
>> if (code == CONST_DOUBLE)
>> return -7;
>> if (code == CONST_FIXED)
>>
>> I think it should be the same as CONST_DOUBLE which it "replaces".
>> Likewise below, that avoids code generation changes (which there should
>> be none for a target that is converted, right?).
> not clear because it does not really replace const double - remember
> that const double still holds fp stuff. another one for richard to
> comment on.
I think it should be the same as CONST_INT. Whether an integer
fits into a HWI or not shouldn't affect its precedence.
>> +/* This is the maximal size of the buffer needed for dump. */
>> +const int MAX = (MAX_BITSIZE_MODE_ANY_INT / 4
>> + + MAX_BITSIZE_MODE_ANY_INT / HOST_BITS_PER_WIDE_INT + 32);
>>
>> I'd prefer a target macro for this, not anything based off
>> MAX_BITSIZE_MODE_ANY_INT just to allow no-op transition of a
>> target to wide-ints (which IMHO should be the default for all targets,
>> simplifying the patch).
Kenny didn't comment on this, but I disagree. Part of the process of
"converting" a port is to ween it off any assumptions about the number
of HWIs.
Richard
