On Sat, 28 Nov 2020, Jakub Jelinek wrote:
> Hi!
>
> As discussed in the PR, e.g. on x86_64 (both -m32 and -m64) there is no
> double-word modulo and so we expand it to a __{,u}mod[dt]i3 call.
> For certain constant divisors we can do better. E.g. consider
> 32-bit word-size, 0x100000000ULL % 3 == 1, so we can use partly the Hacker's
> delight modulo by summing digits approach and optimize
> unsigned long long foo (unsigned long long x) { return x % 3; }
> as
> unsigned long long foo (unsigned long long x) {
> unsigned int sum, carry;
> carry = __builtin_add_overflow ((unsigned int) x, (unsigned int) (x >> 32),
> &sum);
> sum += carry;
> return sum % 3;
> }
> Similarly, 0x10000000ULL % 5 == 1 (note, 1 << 28), so
> unsigned long long bar (unsigned long long x) { return x % 5; }
> as
> unsigned long long bar (unsigned long long x) {
> unsigned int sum = x & ((1 << 28) - 1);
> sum += (x >> 28) & ((1 << 28) - 1);
> sum += (x >> 56);
> return sum % 5;
> }
> etc.
> And we can do also signed modulo,
> long long baz (long long x) { return x % 5; }
> as
> long long baz (long long x) {
> unsigned int sum = x & ((1 << 28) - 1);
> sum += ((unsigned long long) x >> 28) & ((1 << 28) - 1);
> sum += ((unsigned long long) x >> 56);
> /* Sum adjustment for negative x. */
> sum += (x >> 63) & 3;
> unsigned int rem = sum % 5;
> /* And finally adjust it to the right interval for negative values. */
> return (int) (rem + ((x >> 63) & -4));
> }
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2020-11-28 Jakub Jelinek <[email protected]>
>
> PR rtl-optimization/97459
> * internal-fn.h (expand_addsub_overflow): Declare.
> * internal-fn.c (expand_addsub_overflow): No longer static.
> * optabs.c (expand_doubleword_mod): New function.
> (expand_binop): Optimize double-word mod with constant divisor.
>
> * gcc.dg/pr97459-1.c: New test.
> * gcc.dg/pr97459-2.c: New test.
>
> --- gcc/internal-fn.h.jj 2020-11-27 11:19:37.950190425 +0100
> +++ gcc/internal-fn.h 2020-11-27 13:18:13.116798464 +0100
> @@ -224,6 +224,8 @@ extern bool internal_gather_scatter_fn_s
> extern bool internal_check_ptrs_fn_supported_p (internal_fn, tree,
> poly_uint64, unsigned int);
>
> +extern void expand_addsub_overflow (location_t, tree_code, tree, tree, tree,
> + bool, bool, bool, bool, tree *);
> extern void expand_internal_call (gcall *);
> extern void expand_internal_call (internal_fn, gcall *);
> extern void expand_PHI (internal_fn, gcall *);
> --- gcc/internal-fn.c.jj 2020-11-27 11:19:37.950190425 +0100
> +++ gcc/internal-fn.c 2020-11-27 13:18:13.117798453 +0100
> @@ -798,7 +798,7 @@ expand_ubsan_result_store (rtx target, r
> /* Add sub/add overflow checking to the statement STMT.
> CODE says whether the operation is +, or -. */
>
> -static void
> +void
> expand_addsub_overflow (location_t loc, tree_code code, tree lhs,
> tree arg0, tree arg1, bool unsr_p, bool uns0_p,
> bool uns1_p, bool is_ubsan, tree *datap)
> --- gcc/optabs.c.jj 2020-11-27 11:19:38.000189859 +0100
> +++ gcc/optabs.c 2020-11-27 16:06:30.971435747 +0100
> @@ -44,6 +44,8 @@ along with GCC; see the file COPYING3.
> #include "expr.h"
> #include "optabs-tree.h"
> #include "libfuncs.h"
> +#include "internal-fn.h"
> +#include "langhooks.h"
>
> static void prepare_float_lib_cmp (rtx, rtx, enum rtx_code, rtx *,
> machine_mode *);
> @@ -926,6 +928,196 @@ expand_doubleword_mult (machine_mode mod
> emit_move_insn (product_high, adjust);
> return product;
> }
> +
> +/* Subroutine of expand_binop. Optimize unsigned double-word OP0 % OP1 for
> + constant OP1. If for some bit in [BITS_PER_WORD / 2, BITS_PER_WORD] range
> + (prefer higher bits) ((1w << bit) % OP1) == 1, then the modulo can be
> + computed in word-mode as ((OP0 & (bit - 1)) + ((OP0 >> bit) & (bit - 1))
> + + (OP0 >> (2 * bit))) % OP1. Whether we need to sum 2, 3 or 4 values
> + depends on the bit value, if 2, then carry from the addition needs to be
> + added too, i.e. like:
> + sum += __builtin_add_overflow (low, high, &sum)
> +
> + Optimize signed double-word OP0 % OP1 similarly, just apply some
> correction
> + factor to the sum before doing unsigned remainder, in the form of
> + sum += (((signed) OP0 >> (2 * BITS_PER_WORD - 1)) & const);
> + then perform unsigned
> + remainder = sum % OP1;
> + and finally
> + remainder += ((signed) OP0 >> (2 * BITS_PER_WORD - 1)) & (1 - OP1); */
> +
> +static rtx
> +expand_doubleword_mod (machine_mode mode, rtx op0, rtx op1, bool unsignedp)
> +{
> + if (INTVAL (op1) <= 1)
> + return NULL_RTX;
> +
> + rtx_insn *last = get_last_insn ();
> + for (int bit = BITS_PER_WORD; bit >= BITS_PER_WORD / 2; bit--)
> + {
> + wide_int w = wi::shifted_mask (bit, 1, false, 2 * BITS_PER_WORD);
> + if (wi::ne_p (wi::umod_trunc (w, INTVAL (op1)), 1))
> + continue;
> + rtx sum = NULL_RTX, mask = NULL_RTX;
> + if (bit == BITS_PER_WORD)
> + {
> + /* For signed modulo we need to add correction to the sum
> + and that might again overflow. */
> + if (!unsignedp)
> + continue;
> + if (optab_handler (uaddv4_optab, word_mode) == CODE_FOR_nothing)
> + continue;
> + tree wtype = lang_hooks.types.type_for_mode (word_mode, 1);
> + if (wtype == NULL_TREE)
> + continue;
> + tree ctype = build_complex_type (wtype);
> + if (TYPE_MODE (ctype) != GET_MODE_COMPLEX_MODE (word_mode))
> + continue;
> + machine_mode cmode = TYPE_MODE (ctype);
> + rtx op00 = operand_subword_force (op0, 0, mode);
> + rtx op01 = operand_subword_force (op0, 1, mode);
> + rtx cres = gen_rtx_CONCAT (cmode, gen_reg_rtx (word_mode),
> + gen_reg_rtx (word_mode));
> + tree lhs = make_tree (ctype, cres);
> + tree arg0 = make_tree (wtype, op00);
> + tree arg1 = make_tree (wtype, op01);
> + expand_addsub_overflow (UNKNOWN_LOCATION, PLUS_EXPR, lhs, arg0,
> + arg1, true, true, true, false, NULL);
> + sum = expand_simple_binop (word_mode, PLUS, XEXP (cres, 0),
> + XEXP (cres, 1), NULL_RTX, 1,
> + OPTAB_DIRECT);
> + if (sum == NULL_RTX)
> + return NULL_RTX;
> + }
> + else
> + {
> + /* Code below uses GEN_INT, so we need the masks to be representable
> + in HOST_WIDE_INTs. */
> + if (bit >= HOST_BITS_PER_WIDE_INT)
> + continue;
> + /* If op0 is e.g. -1 or -2 unsigned, then the 2 additions might
> + overflow. Consider 64-bit -1ULL for word size 32, if we add
> + 0x7fffffffU + 0x7fffffffU + 3U, it wraps around to 1. */
> + if (bit == BITS_PER_WORD - 1)
> + continue;
> +
> + int count = (2 * BITS_PER_WORD + bit - 1) / bit;
> + rtx sum_corr = NULL_RTX;
> +
> + if (!unsignedp)
> + {
> + /* For signed modulo, compute it as unsigned modulo of
> + sum with a correction added to it if OP0 is negative,
> + such that the result can be computed as unsigned
> + remainder + ((OP1 >> (2 * BITS_PER_WORD - 1)) & (1 - OP1). */
> + w = wi::min_value (2 * BITS_PER_WORD, SIGNED);
> + wide_int wmod1 = wi::umod_trunc (w, INTVAL (op1));
> + wide_int wmod2 = wi::smod_trunc (w, INTVAL (op1));
> + /* wmod2 == -wmod1. */
> + wmod2 = wmod2 + (INTVAL (op1) - 1);
> + if (wi::ne_p (wmod1, wmod2))
> + {
> + wide_int wcorr = wmod2 - wmod1;
> + if (wi::neg_p (w))
> + wcorr = wcorr + INTVAL (op1);
> + /* Now verify if the count sums can't overflow, and punt
> + if they could. */
> + w = wi::mask (bit, false, 2 * BITS_PER_WORD);
> + w = w * (count - 1);
> + w = w + wi::mask (2 * BITS_PER_WORD - (count - 1) * bit,
> + false, 2 * BITS_PER_WORD);
> + w = w + wcorr;
> + w = wi::lrshift (w, BITS_PER_WORD);
> + if (wi::ne_p (w, 0))
> + continue;
> +
> + mask = operand_subword_force (op0, WORDS_BIG_ENDIAN ? 0 : 1,
> + mode);
> + mask = expand_simple_binop (word_mode, ASHIFTRT, mask,
> + GEN_INT (BITS_PER_WORD - 1),
> + NULL_RTX, 0, OPTAB_DIRECT);
> + if (mask == NULL_RTX)
> + return NULL_RTX;
> + sum_corr = immed_wide_int_const (wcorr, word_mode);
> + sum_corr = expand_simple_binop (word_mode, AND, mask,
> + sum_corr, NULL_RTX, 1,
> + OPTAB_DIRECT);
> + if (sum_corr == NULL_RTX)
> + return NULL_RTX;
> + }
> + }
> +
> + for (int i = 0; i < count; i++)
> + {
> + rtx v = op0;
> + if (i)
> + v = expand_simple_binop (mode, LSHIFTRT, v, GEN_INT (i * bit),
> + NULL_RTX, 1, OPTAB_DIRECT);
> + if (v == NULL_RTX)
> + return NULL_RTX;
> + v = lowpart_subreg (word_mode, v, mode);
> + if (v == NULL_RTX)
> + return NULL_RTX;
> + if (i != count - 1)
> + v = expand_simple_binop (word_mode, AND, v,
> + GEN_INT ((HOST_WIDE_INT_1U << bit)
> + - 1), NULL_RTX, 1,
> + OPTAB_DIRECT);
> + if (v == NULL_RTX)
> + return NULL_RTX;
> + if (sum == NULL_RTX)
> + sum = v;
> + else
> + sum = expand_simple_binop (word_mode, PLUS, sum, v, NULL_RTX,
> + 1, OPTAB_DIRECT);
> + if (sum == NULL_RTX)
> + return NULL_RTX;
> + }
> + if (sum_corr)
> + {
> + sum = expand_simple_binop (word_mode, PLUS, sum, sum_corr,
> + NULL_RTX, 1, OPTAB_DIRECT);
> + if (sum == NULL_RTX)
> + return NULL_RTX;
> + }
> + }
> + rtx remainder = expand_divmod (1, TRUNC_MOD_EXPR, word_mode, sum, op1,
> + NULL_RTX, 1);
> + if (remainder == NULL_RTX)
> + return NULL_RTX;
> +
> + if (!unsignedp)
> + {
> + if (mask == NULL_RTX)
> + {
> + mask = operand_subword_force (op0, WORDS_BIG_ENDIAN ? 0 : 1,
> + mode);
> + mask = expand_simple_binop (word_mode, ASHIFTRT, mask,
> + GEN_INT (BITS_PER_WORD - 1),
> + NULL_RTX, 0, OPTAB_DIRECT);
> + if (mask == NULL_RTX)
> + return NULL_RTX;
> + }
> + mask = expand_simple_binop (word_mode, AND, mask,
> + GEN_INT (1 - INTVAL (op1)),
> + NULL_RTX, 1, OPTAB_DIRECT);
> + if (mask == NULL_RTX)
> + return NULL_RTX;
> + remainder = expand_simple_binop (word_mode, PLUS, remainder,
> + mask, NULL_RTX, 1, OPTAB_DIRECT);
> + if (remainder == NULL_RTX)
> + return NULL_RTX;
> + }
> +
> + remainder = convert_modes (mode, word_mode, remainder, unsignedp);
> + /* Punt if we need any library calls. */
> + for (; last; last = NEXT_INSN (last))
> + if (CALL_P (last))
> + return NULL_RTX;
> + return remainder;
> + }
> + return NULL_RTX;
> +}
>
> /* Wrapper around expand_binop which takes an rtx code to specify
> the operation to perform, not an optab pointer. All other
> @@ -1806,6 +1998,37 @@ expand_binop (machine_mode mode, optab b
> }
> }
>
> + /* Attempt to synthetize double word modulo by constant divisor. */
> + if ((binoptab == umod_optab || binoptab == smod_optab)
> + && optimize
> + && CONST_INT_P (op1)
> + && is_int_mode (mode, &int_mode)
> + && GET_MODE_SIZE (int_mode) == 2 * UNITS_PER_WORD
> + && optab_handler (lshr_optab, int_mode) != CODE_FOR_nothing
> + && optab_handler (and_optab, word_mode) != CODE_FOR_nothing
> + && optab_handler (add_optab, word_mode) != CODE_FOR_nothing
> + && optimize_insn_for_speed_p ())
> + {
> + rtx remainder = expand_doubleword_mod (int_mode, op0, op1,
> + binoptab == umod_optab);
> + if (remainder != NULL_RTX)
> + {
> + if (optab_handler (mov_optab, int_mode) != CODE_FOR_nothing)
> + {
> + rtx_insn *move = emit_move_insn (target ? target : remainder,
> + remainder);
> + set_dst_reg_note (move,
> + REG_EQUAL,
> + gen_rtx_fmt_ee (UMOD, int_mode,
> + copy_rtx (op0), op1),
> + target ? target : remainder);
> + }
> + return remainder;
> + }
> + else
> + delete_insns_since (last);
> + }
> +
> /* It can't be open-coded in this mode.
> Use a library call if one is available and caller says that's ok. */
>
> --- gcc/testsuite/gcc.dg/pr97459-1.c.jj 2020-11-27 14:16:50.735828637
> +0100
> +++ gcc/testsuite/gcc.dg/pr97459-1.c 2020-11-27 14:16:12.212259188 +0100
> @@ -0,0 +1,54 @@
> +/* PR rtl-optimization/97459 */
> +/* { dg-do run } */
> +/* { dg-options "-O2" } */
> +/* { dg-additional-options "-DEXPENSIVE" { target run_expensive_tests } } */
> +
> +#ifdef __SIZEOF_INT128__
> +typedef __uint128_t T;
> +#else
> +typedef unsigned long long T;
> +#endif
> +
> +T __attribute__((noipa)) foo (T x, T n) { return x % n; }
> +#define C(n) T __attribute__((noipa)) foo##n (T x) { return x % (n - 10000);
> }
> +
> +#define C1(n) C(n##1) C(n##3) C(n##5) C(n##7) C(n##9)
> +#define C2(n) C1(n##0) C1(n##1) C1(n##2) C1(n##3) C1(n##4) \
> + C1(n##5) C1(n##6) C1(n##7) C1(n##8) C1(n##9)
> +#ifdef EXPENSIVE
> +#define C3(n) C2(n##0) C2(n##1) C2(n##2) C2(n##3) C2(n##4) \
> + C2(n##5) C2(n##6) C2(n##7) C2(n##8) C2(n##9)
> +#define C4(n) C3(n##0) C3(n##1) C3(n##2) C3(n##3) C3(n##4) \
> + C3(n##5) C3(n##6) C3(n##7) C3(n##8) C3(n##9)
> +#else
> +#define C3(n) C2(n##0) C2(n##4) C2(n##9)
> +#define C4(n) C3(n##0) C3(n##3) C3(n##7)
> +#endif
> +#define TESTS C4(1)
> +
> +TESTS
> +
> +struct S { T x; T (*foo) (T); };
> +
> +#undef C
> +#define C(n) { n - 10000, foo##n },
> +
> +struct S tests[] = {
> +TESTS
> + { 0, 0 }
> +};
> +
> +int
> +main ()
> +{
> + int i, j, k;
> + for (k = 0; tests[k].x; k++)
> + for (i = 0; i < sizeof (T) * __CHAR_BIT__; i++)
> + for (j = -5; j <= 5; j++)
> + {
> + T x = ((T) 1 << i) + j;
> + if (foo (x, tests[k].x) != tests[k].foo (x))
> + __builtin_abort ();
> + }
> + return 0;
> +}
> --- gcc/testsuite/gcc.dg/pr97459-2.c.jj 2020-11-27 15:53:36.831080388
> +0100
> +++ gcc/testsuite/gcc.dg/pr97459-2.c 2020-11-27 15:50:20.763269826 +0100
> @@ -0,0 +1,57 @@
> +/* PR rtl-optimization/97459 */
> +/* { dg-do run } */
> +/* { dg-options "-O2" } */
> +/* { dg-additional-options "-DEXPENSIVE" { target run_expensive_tests } } */
> +
> +#ifdef __SIZEOF_INT128__
> +typedef __int128_t T;
> +typedef __uint128_t U;
> +#else
> +typedef long long T;
> +typedef unsigned long long U;
> +#endif
> +
> +T __attribute__((noipa)) foo (T x, T n) { return x % n; }
> +#define C(n) T __attribute__((noipa)) foo##n (T x) { return x % (n - 10000);
> }
> +
> +#define C1(n) C(n##1) C(n##3) C(n##5) C(n##7) C(n##9)
> +#define C2(n) C1(n##0) C1(n##1) C1(n##2) C1(n##3) C1(n##4) \
> + C1(n##5) C1(n##6) C1(n##7) C1(n##8) C1(n##9)
> +#ifdef EXPENSIVE
> +#define C3(n) C2(n##0) C2(n##1) C2(n##2) C2(n##3) C2(n##4) \
> + C2(n##5) C2(n##6) C2(n##7) C2(n##8) C2(n##9)
> +#define C4(n) C3(n##0) C3(n##1) C3(n##2) C3(n##3) C3(n##4) \
> + C3(n##5) C3(n##6) C3(n##7) C3(n##8) C3(n##9)
> +#else
> +#define C3(n) C2(n##0) C2(n##4) C2(n##9)
> +#define C4(n) C3(n##0) C3(n##3) C3(n##7)
> +#endif
> +#define TESTS C4(1)
> +
> +TESTS
> +
> +struct S { T x; T (*foo) (T); };
> +
> +#undef C
> +#define C(n) { n - 10000, foo##n },
> +
> +struct S tests[] = {
> +TESTS
> + { 0, 0 }
> +};
> +
> +int
> +main ()
> +{
> + int i, j, k;
> + for (k = 0; tests[k].x; k++)
> + for (i = 0; i < sizeof (T) * __CHAR_BIT__; i++)
> + for (j = -5; j <= 5; j++)
> + {
> + U x = ((U) 1 << i) + j;
> + if (foo ((T) x, tests[k].x) != tests[k].foo ((T) x)
> + || foo ((T) -x, tests[k].x) != tests[k].foo ((T) -x))
> + __builtin_abort ();
> + }
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
