On Fri, Jul 8, 2022 at 5:54 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> 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.
Fixed.
> > + 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
Fixed.
> (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
There are a few comparisons. Should I limit it to 4 bytes?
> 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
memchr("abcd", a, 4) == 0 is optimized to
(a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
by this patch.
> 'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't
It works only for memchr("aaaa", a, 4) == 0. It is optimized to
x != 'a' by this patch.
Thanks.
> 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
> >
--
H.J.
