On Thu, Jul 7, 2022 at 6:45 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> When memchr is applied on a constant string of no more than the bytes of
> a word, simplify memchr by checking each byte in the constant string.
>
> int f (int a)
> {
> return __builtin_memchr ("AE", a, 2) != 0;
> }
>
> is simplified to
>
> int f (int a)
> {
> return ((char) a == 'A' || (char) a == 'E') != 0;
> }
>
> gcc/
>
> PR tree-optimization/103798
> * tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
> (simplify_builtin_call): Inline memchr with constant strings of
> no more than the bytes of a word.
> * tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
> * tree-ssa-strlen.h (use_in_zero_equality): New.
>
> gcc/testsuite/
>
> PR tree-optimization/103798
> * c-c++-common/pr103798-1.c: New test.
> * c-c++-common/pr103798-2.c: Likewise.
> * c-c++-common/pr103798-3.c: Likewise.
> * c-c++-common/pr103798-4.c: Likewise.
> * c-c++-common/pr103798-5.c: Likewise.
> * c-c++-common/pr103798-6.c: Likewise.
> * c-c++-common/pr103798-7.c: Likewise.
> * c-c++-common/pr103798-8.c: Likewise.
> ---
> gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
> gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
> gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
> gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
> gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
> gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
> gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
> gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
> gcc/tree-ssa-forwprop.cc | 64 +++++++++++++++++++++++++
> gcc/tree-ssa-strlen.cc | 4 +-
> gcc/tree-ssa-strlen.h | 2 +
> 11 files changed, 289 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
> create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
>
> diff --git a/gcc/testsuite/c-c++-common/pr103798-1.c
> b/gcc/testsuite/c-c++-common/pr103798-1.c
> new file mode 100644
> index 00000000000..cd3edf569fc
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-1.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> + return __builtin_memchr ("a", a, 1) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> + return a != 'a';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c
> b/gcc/testsuite/c-c++-common/pr103798-2.c
> new file mode 100644
> index 00000000000..e7e99c3679e
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-2.c
> @@ -0,0 +1,30 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +#include <string.h>
> +
> +__attribute__ ((weak))
> +int
> +f (int a)
> +{
> + return memchr ("aE", a, 2) != NULL;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> + return a == 'a' || a == 'E';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i + 256) != g (i + 256))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-3.c
> b/gcc/testsuite/c-c++-common/pr103798-3.c
> new file mode 100644
> index 00000000000..ddcedc7e238
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-3.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> + return __builtin_memchr ("aEgZ", a, 3) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> + return a != 'a' && a != 'E' && a != 'g';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-4.c
> b/gcc/testsuite/c-c++-common/pr103798-4.c
> new file mode 100644
> index 00000000000..00e8302a833
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-4.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> + return __builtin_memchr ("aEgi", a, 4) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> + return a == 'a' || a == 'E' || a == 'g' || a == 'i';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-5.c
> b/gcc/testsuite/c-c++-common/pr103798-5.c
> new file mode 100644
> index 00000000000..0d6487a13df
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-5.c
> @@ -0,0 +1,26 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> + return __builtin_memchr ("aEgiH", a, 5) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> + return a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-6.c
> b/gcc/testsuite/c-c++-common/pr103798-6.c
> new file mode 100644
> index 00000000000..5ccb5ee66e0
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-6.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> + return __builtin_memchr ("aEgiHx", a, 6) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> + return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> + || a == 'x');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-7.c
> b/gcc/testsuite/c-c++-common/pr103798-7.c
> new file mode 100644
> index 00000000000..40fd38257d1
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-7.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> + return __builtin_memchr ("aEgiHjZ", a, 7) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> + return (a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H'
> + && a != 'j' && a != 'Z');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i) != g (i))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-8.c
> b/gcc/testsuite/c-c++-common/pr103798-8.c
> new file mode 100644
> index 00000000000..0841b18cea4
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-8.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(int a)
> +{
> + return __builtin_memchr ("aEgiHx19ABC", a, 8) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> + return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> + || a == 'x' || a == '1' || a == '9');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> + if (f (i + 256) != g (i + 256))
> + __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index 69567ab3275..edd1277c23b 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-dfa.h"
> #include "tree-ssa-propagate.h"
> #include "tree-ssa-dom.h"
> +#include "tree-ssa-strlen.h"
> #include "builtins.h"
> #include "tree-cfgcleanup.h"
> #include "cfganal.h"
> @@ -1177,6 +1178,15 @@ constant_pointer_difference (tree p1, tree p2)
> memcpy (p, "abcd ", 7);
> call if the latter can be stored by pieces during expansion.
>
> + Optimize
> + memchr ("abcd", a, 4) == 0;
> + or
> + memchr ("abcd", a, 4) != 0;
> + to
> + (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> + or
> + (a == 'a' || a == 'b' || a == 'c' || a == 'd') != 0
> +
> Also canonicalize __atomic_fetch_op (p, x, y) op x
> to __atomic_op_fetch (p, x, y) or
> __atomic_op_fetch (p, x, y) iop x
> @@ -1193,8 +1203,62 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p,
> tree callee2)
> return false;
> stmt1 = SSA_NAME_DEF_STMT (vuse);
>
> + tree res;
> +
> switch (DECL_FUNCTION_CODE (callee2))
> {
> + case BUILT_IN_MEMCHR:
> + if (gimple_call_num_args (stmt2) == 3
> + && (res = gimple_call_lhs (stmt2)) != nullptr
> + && use_in_zero_equality (res) != nullptr
> + && CHAR_BIT == 8
> + && BITS_PER_UNIT == 8)
> + {
> + tree ptr = gimple_call_arg (stmt2, 0);
> + if (TREE_CODE (ptr) != ADDR_EXPR
> + || TREE_CODE (TREE_OPERAND (ptr, 0)) != STRING_CST)
> + break;
> + unsigned HOST_WIDE_INT slen
> + = TREE_STRING_LENGTH (TREE_OPERAND (ptr, 0));
> + /* It must be a non-empty string constant. */
> + if (slen < 2)
> + break;
> + tree size = gimple_call_arg (stmt2, 2);
> + /* Size must be a constant which is <= UNITS_PER_WORD and
> + <= the string length. */
> + if (TREE_CODE (size) != INTEGER_CST
> + || integer_zerop (size)
> + || wi::gtu_p (wi::to_wide (size), UNITS_PER_WORD)
> + || wi::geu_p (wi::to_wide (size), slen))
it might be convenient to check tree_fits_uhwi_p (size) and
do unsigned HOST_WIDE_INT sz = tree_to_uhwi (size); instead
of playing with wide-int here.
> + break;
> + tree ch = gimple_call_arg (stmt2, 1);
> + location_t loc = gimple_location (stmt2);
> + if (!useless_type_conversion_p (char_type_node,
> + TREE_TYPE (ch)))
> + ch = fold_convert_loc (loc, char_type_node, ch);
> + const char *p = TREE_STRING_POINTER (TREE_OPERAND (ptr, 0));
> + unsigned int isize = TREE_INT_CST_LOW (size);
> + tree *op = new tree[isize];
> + for (unsigned int i = 0; i < isize; i++)
> + {
> + op[i] = build_int_cst (char_type_node, p[i]);
> + op[i] = fold_build2_loc (loc, EQ_EXPR, boolean_type_node,
> + op[i], ch);
> + }
> + for (unsigned int i = isize - 1; i >= 1; i--)
> + op[i - 1] = fold_convert_loc (loc, boolean_type_node,
> + fold_build2_loc (loc,
> + BIT_IOR_EXPR,
> + boolean_type_node,
> + op[i - 1],
> + op[i]));
> + res = fold_convert_loc (loc, TREE_TYPE (res), op[0]);
> + gimplify_and_update_call_from_tree (gsi_p, res);
my worry about -Os remains, can you please add a check
like optimize_bb_for_speed (gimple_bb (stmt2)) || sz <= 2
(so we allow inline expanding two comparisons when not optimizing
for speed)? For UNITS_PER_WORD == 8 this is possibly a
lot of compares, don't we have some _BY_PIECEs limit we
can use here? There's no COMPARE_RATIO it seems,
not sure what we use there.
Since we only inline expand memchr(..) != 0 we're leaving
'a' != x | 'b' != x | ... optimization to possibly
'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't
do anything like that). The x "splat" needs log2 (sz) operations
(but they might be slow?), but in the end it might pay off
for power-of-two (sz) (one could even do this in chunks)?
Anyway, this might be for a followup.
Otherwise it looks OK.
Thanks,
Richard.
> + delete[] op;
> + return true;
> + }
> + break;
> +
> case BUILT_IN_MEMSET:
> if (gimple_call_num_args (stmt2) != 3
> || gimple_call_lhs (stmt2)
> diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> index 7b3e3899ea2..5afbae1b72e 100644
> --- a/gcc/tree-ssa-strlen.cc
> +++ b/gcc/tree-ssa-strlen.cc
> @@ -3913,8 +3913,8 @@ strlen_pass::handle_builtin_memset (bool *zero_write)
> nonnull if and only RES is used in such expressions exclusively and
> in none other. */
>
> -static gimple *
> -use_in_zero_equality (tree res, bool exclusive = true)
> +gimple *
> +use_in_zero_equality (tree res, bool exclusive)
> {
> gimple *first_use = NULL;
>
> diff --git a/gcc/tree-ssa-strlen.h b/gcc/tree-ssa-strlen.h
> index 8d155450db8..fdb4d9d7783 100644
> --- a/gcc/tree-ssa-strlen.h
> +++ b/gcc/tree-ssa-strlen.h
> @@ -35,6 +35,8 @@ struct c_strlen_data;
> extern void get_range_strlen_dynamic (tree, gimple *, c_strlen_data *,
> pointer_query &);
>
> +extern gimple *use_in_zero_equality (tree, bool = true);
> +
> /* APIs internal to strlen pass. Defined in gimple-ssa-sprintf.cc. */
> extern bool handle_printf_call (gimple_stmt_iterator *, pointer_query &);
>
> --
> 2.36.1
>
