[PATCH v2 3/9] Introduce can_vector_compare_p function
Richard Sandiford
richard.sandiford@arm.com
Tue Aug 27 08:07:00 GMT 2019
Ilya Leoshkevich <iii@linux.ibm.com> writes:
>> Am 26.08.2019 um 15:17 schrieb Ilya Leoshkevich <iii@linux.ibm.com>:
>>
>>> Am 26.08.2019 um 15:06 schrieb Richard Biener <richard.guenther@gmail.com>:
>>>
>>> On Mon, Aug 26, 2019 at 1:54 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>>>>
>>>>> Am 26.08.2019 um 10:49 schrieb Richard Biener <richard.guenther@gmail.com>:
>>>>>
>>>>> On Fri, Aug 23, 2019 at 1:35 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>>>>>>
>>>>>>> Am 23.08.2019 um 13:24 schrieb Richard Biener <richard.guenther@gmail.com>:
>>>>>>>
>>>>>>> On Fri, Aug 23, 2019 at 12:43 PM Richard Sandiford
>>>>>>> <richard.sandiford@arm.com> wrote:
>>>>>>>>
>>>>>>>> Ilya Leoshkevich <iii@linux.ibm.com> writes:
>>>>>>>>> @@ -3819,6 +3820,82 @@ can_compare_p (enum rtx_code code, machine_mode mode,
>>>>>>>>> return 0;
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> +/* can_vector_compare_p presents fake rtx binary operations to the the back-end
>>>>>>>>> + in order to determine its capabilities. In order to avoid creating fake
>>>>>>>>> + operations on each call, values from previous calls are cached in a global
>>>>>>>>> + cached_binops hash_table. It contains rtxes, which can be looked up using
>>>>>>>>> + binop_keys. */
>>>>>>>>> +
>>>>>>>>> +struct binop_key {
>>>>>>>>> + enum rtx_code code; /* Operation code. */
>>>>>>>>> + machine_mode value_mode; /* Result mode. */
>>>>>>>>> + machine_mode cmp_op_mode; /* Operand mode. */
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +struct binop_hasher : pointer_hash_mark<rtx>, ggc_cache_remove<rtx> {
>>>>>>>>> + typedef rtx value_type;
>>>>>>>>> + typedef binop_key compare_type;
>>>>>>>>> +
>>>>>>>>> + static hashval_t
>>>>>>>>> + hash (enum rtx_code code, machine_mode value_mode, machine_mode cmp_op_mode)
>>>>>>>>> + {
>>>>>>>>> + inchash::hash hstate (0);
>>>>>>>>> + hstate.add_int (code);
>>>>>>>>> + hstate.add_int (value_mode);
>>>>>>>>> + hstate.add_int (cmp_op_mode);
>>>>>>>>> + return hstate.end ();
>>>>>>>>> + }
>>>>>>>>> +
>>>>>>>>> + static hashval_t
>>>>>>>>> + hash (const rtx &ref)
>>>>>>>>> + {
>>>>>>>>> + return hash (GET_CODE (ref), GET_MODE (ref), GET_MODE (XEXP (ref, 0)));
>>>>>>>>> + }
>>>>>>>>> +
>>>>>>>>> + static bool
>>>>>>>>> + equal (const rtx &ref1, const binop_key &ref2)
>>>>>>>>> + {
>>>>>>>>> + return (GET_CODE (ref1) == ref2.code)
>>>>>>>>> + && (GET_MODE (ref1) == ref2.value_mode)
>>>>>>>>> + && (GET_MODE (XEXP (ref1, 0)) == ref2.cmp_op_mode);
>>>>>>>>> + }
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static GTY ((cache)) hash_table<binop_hasher> *cached_binops;
>>>>>>>>> +
>>>>>>>>> +static rtx
>>>>>>>>> +get_cached_binop (enum rtx_code code, machine_mode value_mode,
>>>>>>>>> + machine_mode cmp_op_mode)
>>>>>>>>> +{
>>>>>>>>> + if (!cached_binops)
>>>>>>>>> + cached_binops = hash_table<binop_hasher>::create_ggc (1024);
>>>>>>>>> + binop_key key = { code, value_mode, cmp_op_mode };
>>>>>>>>> + hashval_t hash = binop_hasher::hash (code, value_mode, cmp_op_mode);
>>>>>>>>> + rtx *slot = cached_binops->find_slot_with_hash (key, hash, INSERT);
>>>>>>>>> + if (!*slot)
>>>>>>>>> + *slot = gen_rtx_fmt_ee (code, value_mode, gen_reg_rtx (cmp_op_mode),
>>>>>>>>> + gen_reg_rtx (cmp_op_mode));
>>>>>>>>> + return *slot;
>>>>>>>>> +}
>>>>>>>>
>>>>>>>> Sorry, I didn't mean anything this complicated. I just meant that
>>>>>>>> we should have a single cached rtx that we can change via PUT_CODE and
>>>>>>>> PUT_MODE_RAW for each new query, rather than allocating a new rtx each
>>>>>>>> time.
>>>>>>>>
>>>>>>>> Something like:
>>>>>>>>
>>>>>>>> static GTY ((cache)) rtx cached_binop;
>>>>>>>>
>>>>>>>> rtx
>>>>>>>> get_cached_binop (machine_mode mode, rtx_code code, machine_mode op_mode)
>>>>>>>> {
>>>>>>>> if (cached_binop)
>>>>>>>> {
>>>>>>>> PUT_CODE (cached_binop, code);
>>>>>>>> PUT_MODE_RAW (cached_binop, mode);
>>>>>>>> PUT_MODE_RAW (XEXP (cached_binop, 0), op_mode);
>>>>>>>> PUT_MODE_RAW (XEXP (cached_binop, 1), op_mode);
>>>>>>>> }
>>>>>>>> else
>>>>>>>> {
>>>>>>>> rtx reg1 = gen_raw_REG (op_mode, LAST_VIRTUAL_REGISTER + 1);
>>>>>>>> rtx reg2 = gen_raw_REG (op_mode, LAST_VIRTUAL_REGISTER + 2);
>>>>>>>> cached_binop = gen_rtx_fmt_ee (code, mode, reg1, reg2);
>>>>>>>> }
>>>>>>>> return cached_binop;
>>>>>>>> }
>>>>>>>
>>>>>>> Hmm, maybe we need auto_rtx (code) that constructs such
>>>>>>> RTX on the stack instead of wasting a GC root (and causing
>>>>>>> issues for future threading of GCC ;)).
>>>>>>
>>>>>> Do you mean something like this?
>>>>>>
>>>>>> union {
>>>>>> char raw[rtx_code_size[code]];
>>>>>> rtx rtx;
>>>>>> } binop;
>>>>>>
>>>>>> Does this exist already (git grep auto.*rtx / rtx.*auto doesn't show
>>>>>> anything useful), or should I implement this?
>>>>>
>>>>> It doesn't exist AFAIK, I thought about using alloca like
>>>>>
>>>>> rtx tem;
>>>>> rtx_alloca (tem, PLUS);
>>>>>
>>>>> and due to using alloca rtx_alloca has to be a macro like
>>>>>
>>>>> #define rtx_alloca(r, code) r = (rtx)alloca (RTX_CODE_SIZE(code));
>>>>> memset (r, 0, RTX_HDR_SIZE); PUT_CODE (r, code);
>>>>>
>>>>> maybe C++ can help making this prettier but of course
>>>>> since we use alloca we have to avoid opening new scopes.
>>>>>
>>>>> I guess templates like with auto_vec doesn't work unless
>>>>> we can make RTX_CODE_SIZE constant-evaluated.
>>>>>
>>>>> Richard.
>>>>
>>>> I ended up with the following change:
>>>>
>>>> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
>>>> index a667cdab94e..97aa2144e95 100644
>>>> --- a/gcc/emit-rtl.c
>>>> +++ b/gcc/emit-rtl.c
>>>> @@ -466,17 +466,25 @@ set_mode_and_regno (rtx x, machine_mode mode, unsigned int regno)
>>>> set_regno_raw (x, regno, nregs);
>>>> }
>>>>
>>>> -/* Generate a new REG rtx. Make sure ORIGINAL_REGNO is set properly, and
>>>> +/* Initialize a REG rtx. Make sure ORIGINAL_REGNO is set properly, and
>>>> don't attempt to share with the various global pieces of rtl (such as
>>>> frame_pointer_rtx). */
>>>>
>>>> -rtx
>>>> -gen_raw_REG (machine_mode mode, unsigned int regno)
>>>> +void
>>>> +init_raw_REG (rtx x, machine_mode mode, unsigned int regno)
>>>> {
>>>> - rtx x = rtx_alloc (REG MEM_STAT_INFO);
>>>> set_mode_and_regno (x, mode, regno);
>>>> REG_ATTRS (x) = NULL;
>>>> ORIGINAL_REGNO (x) = regno;
>>>> +}
>>>> +
>>>> +/* Generate a new REG rtx. */
>>>> +
>>>> +rtx
>>>> +gen_raw_REG (machine_mode mode, unsigned int regno)
>>>> +{
>>>> + rtx x = rtx_alloc (REG MEM_STAT_INFO);
>>>> + init_raw_REG (x, mode, regno);
>>>> return x;
>>>> }
>>>>
>>>> diff --git a/gcc/gengenrtl.c b/gcc/gengenrtl.c
>>>> index 5c78fabfb50..bb2087da258 100644
>>>> --- a/gcc/gengenrtl.c
>>>> +++ b/gcc/gengenrtl.c
>>>> @@ -231,8 +231,7 @@ genmacro (int idx)
>>>> puts (")");
>>>> }
>>>>
>>>> -/* Generate the code for the function to generate RTL whose
>>>> - format is FORMAT. */
>>>> +/* Generate the code for functions to generate RTL whose format is FORMAT. */
>>>>
>>>> static void
>>>> gendef (const char *format)
>>>> @@ -240,22 +239,18 @@ gendef (const char *format)
>>>> const char *p;
>>>> int i, j;
>>>>
>>>> - /* Start by writing the definition of the function name and the types
>>>> + /* Write the definition of the init function name and the types
>>>> of the arguments. */
>>>>
>>>> - printf ("static inline rtx\ngen_rtx_fmt_%s_stat (RTX_CODE code, machine_mode mode", format);
>>>> + puts ("static inline void");
>>>> + printf ("init_rtx_fmt_%s (rtx rt, machine_mode mode", format);
>>>> for (p = format, i = 0; *p != 0; p++)
>>>> if (*p != '0')
>>>> printf (",\n\t%sarg%d", type_from_format (*p), i++);
>>>> + puts (")");
>>>>
>>>> - puts (" MEM_STAT_DECL)");
>>>> -
>>>> - /* Now write out the body of the function itself, which allocates
>>>> - the memory and initializes it. */
>>>> + /* Now write out the body of the init function itself. */
>>>> puts ("{");
>>>> - puts (" rtx rt;");
>>>> - puts (" rt = rtx_alloc (code PASS_MEM_STAT);\n");
>>>> -
>>>> puts (" PUT_MODE_RAW (rt, mode);");
>>>>
>>>> for (p = format, i = j = 0; *p ; ++p, ++i)
>>>> @@ -266,16 +261,56 @@ gendef (const char *format)
>>>> else
>>>> printf (" %s (rt, %d) = arg%d;\n", accessor_from_format (*p), i, j++);
>>>>
>>>> - puts ("\n return rt;\n}\n");
>>>> + puts ("}\n");
>>>> +
>>>> + /* Write the definition of the gen function name and the types
>>>> + of the arguments. */
>>>> +
>>>> + puts ("static inline rtx");
>>>> + printf ("gen_rtx_fmt_%s_stat (RTX_CODE code, machine_mode mode", format);
>>>> + for (p = format, i = 0; *p != 0; p++)
>>>> + if (*p != '0')
>>>> + printf (",\n\t%sarg%d", type_from_format (*p), i++);
>>>> + puts (" MEM_STAT_DECL)");
>>>> +
>>>> + /* Now write out the body of the function itself, which allocates
>>>> + the memory and initializes it. */
>>>> + puts ("{");
>>>> + puts (" rtx rt;\n");
>>>> +
>>>> + puts (" rt = rtx_alloc (code PASS_MEM_STAT);");
>>>> + printf (" init_rtx_fmt_%s (rt, mode", format);
>>>> + for (p = format, i = 0; *p != 0; p++)
>>>> + if (*p != '0')
>>>> + printf (", arg%d", i++);
>>>> + puts (");\n");
>>>> +
>>>> + puts (" return rt;\n}\n");
>>>> +
>>>> + /* Write the definition of gen macro. */
>>>> +
>>>> printf ("#define gen_rtx_fmt_%s(c, m", format);
>>>> for (p = format, i = 0; *p != 0; p++)
>>>> if (*p != '0')
>>>> - printf (", p%i",i++);
>>>> - printf (")\\\n gen_rtx_fmt_%s_stat (c, m", format);
>>>> + printf (", arg%d", i++);
>>>> + printf (") \\\n gen_rtx_fmt_%s_stat ((c), (m)", format);
>>>> for (p = format, i = 0; *p != 0; p++)
>>>> if (*p != '0')
>>>> - printf (", p%i",i++);
>>>> + printf (", (arg%d)", i++);
>>>> printf (" MEM_STAT_INFO)\n\n");
>>>> +
>>>> + /* Write the definition of alloca macro. */
>>>> +
>>>> + printf ("#define alloca_rtx_fmt_%s(rt, c, m", format);
>>>> + for (p = format, i = 0; *p != 0; p++)
>>>> + if (*p != '0')
>>>> + printf (", arg%d", i++);
>>>> + printf (") \\\n rtx_alloca ((rt), (c)); \\\n");
>>>> + printf (" init_rtx_fmt_%s ((rt), (m)", format);
>>>> + for (p = format, i = 0; *p != 0; p++)
>>>> + if (*p != '0')
>>>> + printf (", (arg%d)", i++);
>>>> + printf (")\n\n");
>>>> }
>>>>
>>>> /* Generate the documentation header for files we write. */
>>>> diff --git a/gcc/rtl.h b/gcc/rtl.h
>>>> index efb9b3ce40d..44733d8a39e 100644
>>>> --- a/gcc/rtl.h
>>>> +++ b/gcc/rtl.h
>>>> @@ -2933,6 +2933,10 @@ extern HOST_WIDE_INT get_stack_check_protect (void);
>>>>
>>>> /* In rtl.c */
>>>> extern rtx rtx_alloc (RTX_CODE CXX_MEM_STAT_INFO);
>>>> +#define rtx_alloca(rt, code) \
>>>> + (rt) = (rtx) alloca (RTX_CODE_SIZE ((code))); \
>>>> + memset ((rt), 0, RTX_HDR_SIZE); \
>>>> + PUT_CODE ((rt), (code));
>>>> extern rtx rtx_alloc_stat_v (RTX_CODE MEM_STAT_DECL, int);
>>>> #define rtx_alloc_v(c, SZ) rtx_alloc_stat_v (c MEM_STAT_INFO, SZ)
>>>> #define const_wide_int_alloc(NWORDS) \
>>>> @@ -3797,7 +3801,11 @@ gen_rtx_INSN (machine_mode mode, rtx_insn *prev_insn, rtx_insn *next_insn,
>>>> extern rtx gen_rtx_CONST_INT (machine_mode, HOST_WIDE_INT);
>>>> extern rtx gen_rtx_CONST_VECTOR (machine_mode, rtvec);
>>>> extern void set_mode_and_regno (rtx, machine_mode, unsigned int);
>>>> +extern void init_raw_REG (rtx, machine_mode, unsigned int);
>>>> extern rtx gen_raw_REG (machine_mode, unsigned int);
>>>> +#define alloca_raw_REG(rt, mode, regno) \
>>>> + rtx_alloca ((rt), REG); \
>>>> + init_raw_REG ((rt), (mode), (regno))
>>>> extern rtx gen_rtx_REG (machine_mode, unsigned int);
>>>> extern rtx gen_rtx_SUBREG (machine_mode, rtx, poly_uint64);
>>>> extern rtx gen_rtx_MEM (machine_mode, rtx);
>>>>
>>>> which now allows me to write:
>>>>
>>>> rtx reg1, reg2, test;
>>>> alloca_raw_REG (reg1, cmp_op_mode, LAST_VIRTUAL_REGISTER + 1);
>>>> alloca_raw_REG (reg2, cmp_op_mode, LAST_VIRTUAL_REGISTER + 2);
>>>> alloca_rtx_fmt_ee (test, code, value_mode, reg1, reg2);
>>>>
>>>> If that looks ok, I'll resend the series.
>>>
>>> that looks OK to me - please leave Richard S. time to comment. Also while
>>> I'd like to see
>>>
>>> rtx reg1 = alloca_raw_REG (cmp_op_mode, LAST_VIRTUAL_REGISTER + 1);
>>>
>>> I don't really see a way to write that portably (or at all), do you all agree?
>>> GCC doesn't seem to convert alloca() calls to __builtin_stack_save/restore
>>> nor place CLOBBERs to end their lifetime. But is it guaranteed that the
>>> alloca result is valid until frame termination?
>>
>> Hmm, the alloca man page says:
>>
>> The alloca() function allocates size bytes of space in the stack
>> frame of the caller. This temporary space is automatically freed
>> when the function that called alloca() returns to its caller.
>> ...
>> The space allocated by alloca() is not automatically deallocated if
>> the pointer that refers to it simply goes out of scope.
>>
>> A quick experiment with gcc and clang confirms this. I think this means
>> I can make alloca_raw_REG macro return the allocated pointer using the
>> return-from-block GNU extension.
>
> What do you think about the following approach?
>
> extern rtx rtx_init (rtx, RTX_CODE);
> #define rtx_alloca(code) \
> rtx_init ((rtx) alloca (RTX_CODE_SIZE ((code))), (code))
>
> ...
>
> rtx
> rtx_init (rtx rt, RTX_CODE code)
> {
> /* We want to clear everything up to the FLD array. Normally, this
> is one int, but we don't want to assume that and it isn't very
> portable anyway; this is. */
> memset (rt, 0, RTX_HDR_SIZE);
Might as well remove this comment while you're there. RTX_HDR_SIZE
has long ceased to be sizeof (int) for any host.
> PUT_CODE (rt, code);
> return rt;
> }
>
> with similar changes to alloca_raw_REG and gengenrtl. This way we don't
> even need a GNU extension.
Sounds good to me, but rtx_init should probably be an inline function.
Thanks,
Richard
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