Hi!
On 2023-06-30T20:45:38+0800, Kito Cheng <kito.ch...@sifive.com> wrote:
>> On 2023-05-13T16:44:41+0800, Kito Cheng via Gcc-patches
>> <gcc-patches@gcc.gnu.org> wrote:
>> > Tried this patch and I ran into some issues, some variables are using
>> > unsigned char to hold machine mode and will have problems when the
>> > number of modes is larger than 255...
>> >
>> > And here is the fix:
>>
>> > --- a/gcc/genmodes.cc
>> > +++ b/gcc/genmodes.cc
>> > @@ -1141,10 +1141,10 @@ inline __attribute__((__always_inline__))\n\
>> > #else\n\
>> > extern __inline__ __attribute__((__always_inline__, __gnu_inline__))\n\
>> > #endif\n\
>> > -unsigned char\n\
>> > +unsigned short\n\
>> > mode_inner_inline (machine_mode mode)\n\
>> > {\n\
>> > - extern const unsigned char mode_inner[NUM_MACHINE_MODES];\n\
>> > + extern const unsigned short mode_inner[NUM_MACHINE_MODES];\n\
>> > gcc_assert (mode >= 0 && mode < NUM_MACHINE_MODES);\n\
>> > switch (mode)\n\
>> > {");
>> > @@ -1529,7 +1529,7 @@ emit_mode_wider (void)
>> > int c;
>> > struct mode_data *m;
>> >
>> > - print_decl ("unsigned char", "mode_next", "NUM_MACHINE_MODES");
>> > + print_decl ("unsigned short", "mode_next", "NUM_MACHINE_MODES");
>>
>> Etc.
>>
>> Instead of 's%char%short', shouldn't we really be using
>> 'enum machine_mode' here? (I understand such a change may require some
>> further surgery, but wouldn't it be the correct thing to do?)
>
> Hmmm, I think maybe what we need is to leverage C++ language features
> to declare enum with underlying types like that:
>
> enum machine_mode : uint16_t
Eh, so that's the reason/confusion (or, at least some of it...) here: my
(naïve...) assumption has been that 'enum machine_mode' already does have
a fixed underlying type -- but apparently it does not, so defaults to
'unsigned int'!
(gdb) ptype lto_mode_identity_table
type = const enum machine_mode : unsigned int {E_VOIDmode, E_BLKmode,
E_CCmode, [...], NUM_MACHINE_MODES = 130} *
So, yeah, should we fix that, and then generally use 'enum machine_mode'
instead of 'char' vs. 'short'? (Or, which other "detail" do I fail to
recognize this time?)
Grüße
Thomas
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