MATCH: [PR109959] `(uns <= 1) & uns` could be optimized to `uns == 1`

  I noticed while looking into some code generation of bitmap_single_bit_set_p,
that sometimes:
```
  if (uns > 1)
    return 0;
  return uns == 1;
```
Would not optimize down to just:
```
return uns == 1;
```

In this case, VRP likes to change `a == 1` into `(bool)a` if
a has a range of [0,1] due to `a <= 1` side of the branch.
We might end up with this similar code even without VRP,
in the case of builtin-sprintf-warn-23.c (and Wrestrict.c), we had:
```
if (s < 0 || 1 < s)
  s = 0;
```
Which is the same as `s = ((unsigned)s) <= 1 ? s : 0`;
So we should be able to catch that also.

This adds 2 patterns to catch `(uns <= 1) & uns` and
`(uns > 1) ? 0 : uns` and convert those into:
`(convert) uns == 1`.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/109959

gcc/ChangeLog:

	* match.pd (`(a > 1) ? 0 : (cast)a`, `(a <= 1) & (cast)a`):
	New patterns.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/builtin-sprintf-warn-23.c: Remove xfail.
	* c-c++-common/Wrestrict.c: Update test and remove some xfail.
	* gcc.dg/tree-ssa/cmpeq-1.c: New test.
	* gcc.dg/tree-ssa/cmpeq-2.c: New test.
	* gcc.dg/tree-ssa/cmpeq-3.c: New test.
---
 gcc/match.pd                                  | 20 +++++++++++
 gcc/testsuite/c-c++-common/Wrestrict.c        | 11 +++---
 .../gcc.dg/tree-ssa/builtin-sprintf-warn-23.c |  2 +-
 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c       | 36 +++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c       | 32 +++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c       | 22 ++++++++++++
 6 files changed, 117 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c
  

On Mon, Aug 7, 2023 at 7:07 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> I noticed while looking into some code generation of bitmap_single_bit_set_p,
> that sometimes:
> ```
>   if (uns > 1)
>     return 0;
>   return uns == 1;
> ```
> Would not optimize down to just:
> ```
> return uns == 1;
> ```
>
> In this case, VRP likes to change `a == 1` into `(bool)a` if
> a has a range of [0,1] due to `a <= 1` side of the branch.
> We might end up with this similar code even without VRP,
> in the case of builtin-sprintf-warn-23.c (and Wrestrict.c), we had:
> ```
> if (s < 0 || 1 < s)
>   s = 0;
> ```
> Which is the same as `s = ((unsigned)s) <= 1 ? s : 0`;
> So we should be able to catch that also.
>
> This adds 2 patterns to catch `(uns <= 1) & uns` and
> `(uns > 1) ? 0 : uns` and convert those into:
> `(convert) uns == 1`.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

OK.

Thanks,
Richard.

>         PR tree-optimization/109959
>
> gcc/ChangeLog:
>
>         * match.pd (`(a > 1) ? 0 : (cast)a`, `(a <= 1) & (cast)a`):
>         New patterns.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/builtin-sprintf-warn-23.c: Remove xfail.
>         * c-c++-common/Wrestrict.c: Update test and remove some xfail.
>         * gcc.dg/tree-ssa/cmpeq-1.c: New test.
>         * gcc.dg/tree-ssa/cmpeq-2.c: New test.
>         * gcc.dg/tree-ssa/cmpeq-3.c: New test.
> ---
>  gcc/match.pd                                  | 20 +++++++++++
>  gcc/testsuite/c-c++-common/Wrestrict.c        | 11 +++---
>  .../gcc.dg/tree-ssa/builtin-sprintf-warn-23.c |  2 +-
>  gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c       | 36 +++++++++++++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c       | 32 +++++++++++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c       | 22 ++++++++++++
>  6 files changed, 117 insertions(+), 6 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index de54b17abba..9b4819e5be7 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -4902,6 +4902,26 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>   )
>  )
>
> +/* (a > 1) ? 0 : (cast)a is the same as (cast)(a == 1)
> +   for unsigned types. */
> +(simplify
> + (cond (gt @0 integer_onep@1) integer_zerop (convert? @2))
> + (if (TYPE_UNSIGNED (TREE_TYPE (@0))
> +      && bitwise_equal_p (@0, @2))
> +  (convert (eq @0 @1))
> + )
> +)
> +
> +/* (a <= 1) & (cast)a is the same as (cast)(a == 1)
> +   for unsigned types. */
> +(simplify
> + (bit_and:c (convert1? (le @0 integer_onep@1)) (convert2? @2))
> + (if (TYPE_UNSIGNED (TREE_TYPE (@0))
> +      && bitwise_equal_p (@0, @2))
> +  (convert (eq @0 @1))
> + )
> +)
> +
>  (simplify
>   (cond @0 zero_one_valued_p@1 zero_one_valued_p@2)
>   (switch
> diff --git a/gcc/testsuite/c-c++-common/Wrestrict.c b/gcc/testsuite/c-c++-common/Wrestrict.c
> index 9eb02bdbfcb..4d005a618b3 100644
> --- a/gcc/testsuite/c-c++-common/Wrestrict.c
> +++ b/gcc/testsuite/c-c++-common/Wrestrict.c
> @@ -681,7 +681,7 @@ void test_strcpy_range (void)
>    ptrdiff_t r;
>
>    r = SR (0, 1);
> -  T (8, "0", a + r, a);   /* { dg-warning "accessing between 1 and 2 bytes at offsets \\\[0, 1] and 0 overlaps up to 2 bytes at offset \\\[0, 1]" "strcpy" { xfail *-*-*} } */
> +  T (8, "0", a + r, a);   /* { dg-warning "accessing 2 bytes at offsets \\\[0, 1] and 0 overlaps between 1 and 2 bytes at offset \\\[0, 1]" "strcpy" } */
>
>    r = SR (2, 5);
>    T (8, "01",  a + r, a);            /* { dg-warning "accessing 3 bytes at offsets \\\[2, 5] and 0 may overlap 1 byte at offset 2" } */
> @@ -860,10 +860,11 @@ void test_strncpy_range (char *d, size_t n)
>
>    i = SR (0, 1);
>    T ("0123", a, a + i, 0);
> -  T ("0123", a, a + i, 1);
> -  /* Offset in the range [0, i] is represented as a PHI (&a, &a + i)
> -     that the implementation isn't equipped to handle yet.  */
> -  T ("0123", a, a + i, 2);   /* { dg-warning "accessing 2 bytes at offsets 0 and \\\[0, 1] may overlap 1 byte at offset 1" "strncpy" { xfail *-*-* } } */
> +  T ("0123", a, a + i, 1); /* { dg-warning "accessing 1 byte at offsets 0 and \\\[0, 1] may overlap 1 byte at offset 0" } */
> +  /* When i == 1 the following overlaps at least 1 byte: the nul at a[1]
> +     (if a + 1 is the empty string).  If a + 1 is not empty then it overlaps
> +     it plus as many non-nul characters after it, up to the total of 2.  */
> +  T ("0123", a, a + i, 2);   /* { dg-warning "accessing 2 bytes at offsets 0 and \\\[0, 1] overlaps between 1 and 2 bytes at offset \\\[0, 1]" "strncpy" } */
>
>    i = SR (1, 5);
>    T ("0123", a, a + i, 0);
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-23.c b/gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-23.c
> index 112b08afc44..051c58892e6 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-23.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-23.c
> @@ -719,5 +719,5 @@ void test_overlap_with_precision (char *d, int i, int j)
>    T (d, "%.*s", i, d + 0);    /* { dg-warning "may overlap" } */
>    T (d, "%.*s", i, d + 1);    /* { dg-warning "may overlap" } */
>    T (d, "%.*s", i, d + 2);
> -  T (d, "%.*s", i, d + i);    /* { dg-warning "may overlap" "" { xfail *-*-* } } */
> +  T (d, "%.*s", i, d + i);    /* { dg-warning "may overlap" } */
>  }
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c
> new file mode 100644
> index 00000000000..1d5b960b663
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-1.c
> @@ -0,0 +1,36 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +/* PR tree-optimization/109959 */
> +
> +unsigned fu(unsigned a)
> +{
> +        _Bool t = a <= 1;
> +        return t & a;
> +}
> +
> +_Bool fb(unsigned a)
> +{
> +        _Bool t = a <= 1;
> +        return t & a;
> +}
> +
> +_Bool fb1(unsigned a)
> +{
> +        _Bool t = a <= 1;
> +        _Bool t1 = a;
> +        return t & t1;
> +}
> +
> +signed fui(unsigned a)
> +{
> +        _Bool t = a <= 1;
> +        int ai = a;
> +        return t & ai;
> +}
> +
> +/* These all should be optimized to `a == 1` */
> +/* { dg-final { scan-tree-dump-times "eq_expr," 4 "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "le_expr," "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "bit_and_expr," "optimized"} } */
> +
> +
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c
> new file mode 100644
> index 00000000000..c727b9e7143
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-2.c
> @@ -0,0 +1,32 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +/* PR tree-optimization/109959 */
> +
> +unsigned f(unsigned a)
> +{
> +  if (a <= 1)
> +    return a;
> +  return 0;
> +}
> +
> +unsigned f0(unsigned a)
> +{
> +  if (a > 1)
> +    return 0;
> +  return a;
> +}
> +
> +_Bool fb(unsigned a)
> +{
> +  if (a > 1)
> +    return 0;
> +  return a == 1;
> +}
> +
> +/* These all should be optimized to `a == 1` */
> +/* { dg-final { scan-tree-dump-times "eq_expr," 3 "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "le_expr," "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "bit_and," "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "gimple_phi " "optimized"} } */
> +
> +
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c
> new file mode 100644
> index 00000000000..f2546b8813f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpeq-3.c
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +/* PR tree-optimization/109959 */
> +
> +
> +_Bool f2(unsigned a, int t)
> +{
> +  void g(void);
> +  if (t)
> +    return 0;
> +  g();
> +  if (a > 1)
> +    return 0;
> +  return a == 1;
> +}
> +
> +/* These all should be optimized to `a == 1` */
> +/* { dg-final { scan-tree-dump-times "eq_expr," 1 "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "le_expr," "optimized"} } */
> +/* { dg-final { scan-tree-dump-not "bit_and_expr," "optimized"} } */
> +
> +
> --
> 2.31.1
>