On Fri, Jul 7, 2023 at 7:57 PM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> When I moved two_value to match.pd, I removed the check for the {0,+-1}
> as I had placed it after the {0,+-1} case for cond in match.pd.
> In the case of {0,+-1} and non boolean, before we would optmize those
> case to just `(convert)a` but after we would get `(convert)(a != 0)`
> which was not handled anyways to just `(convert)a`.
> So this adds a pattern to match `(convert)(zeroone != 0)` and simplify
> to `(convert)zeroone`.
>
> In the bug report, we do finally optimize `(convert)(zeroone != 0)` to
> `zeroone` in VRP2 but that in itself is too late and we miss other
> optimizations that would have happened.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
> PR tree-optimization/110539
> * match.pd ((convert)(zeroone !=/== 0)): Match
> and simplify to ((convert)zeroone)){,^1}.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/110539
> * gcc.dg/tree-ssa/pr110539-1.c: New test.
> * gcc.dg/tree-ssa/pr110539-2.c: New test.
> * gcc.dg/tree-ssa/pr110539-3.c: New test.
> ---
> gcc/match.pd | 15 +++++
> gcc/testsuite/gcc.dg/tree-ssa/pr110539-1.c | 12 ++++
> gcc/testsuite/gcc.dg/tree-ssa/pr110539-2.c | 12 ++++
> gcc/testsuite/gcc.dg/tree-ssa/pr110539-3.c | 70 ++++++++++++++++++++++
> 4 files changed, 109 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr110539-1.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr110539-2.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr110539-3.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index c709153217a..87767a7778b 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -2060,6 +2060,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (vec_cond:s (icmp@1 @4 @5) @3 integer_zerop))
> (vec_cond @0 @2 @3)))
>
> +#if GIMPLE
> +/* This cannot be done on generic as fold has the
> + exact opposite transformation:
> + `Fold ~X & 1 as (X & 1) == 0.`
> + `Fold (X ^ 1) & 1 as (X & 1) == 0.` */
> +/* (convert)(zeroone != 0) into (convert)zeroone */
Not sure how the comment on GENERIC applies to this one?
> +/* (convert)(zeroone == 0) into (convert)(zeroone^1) */
This OTOH is a canonicalization, and I'm not sure a very good one
since (convert)(zeroone == 0) might be more easily recognized
as setCC and a zero flag might even be present in the def of zeroone?
> +(for neeq (ne eq)
> + (simplify
> + (convert (neeq zero_one_valued_p@0 integer_zerop))
> + (if (neeq == NE_EXPR)
> + (convert @0)
> + (convert (bit_xor @0 { build_one_cst (TREE_TYPE (@0)); } )))))
> +#endif
> +
> /* Transform X & -Y into X * Y when Y is { 0 or 1 }. */
> (simplify
> (bit_and:c (convert? (negate zero_one_valued_p@0)) @1)
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr110539-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-1.c
> new file mode 100644
> index 00000000000..6ba864cdd13
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-1.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fdump-tree-optimized" } */
> +int f(int a)
> +{
> + int b = a & 1;
> + int c = b != 0;
> + return c == b;
> +}
> +
> +/* This should be optimized to just return 1; */
> +/* { dg-final { scan-tree-dump-not " == " "optimized"} } */
> +/* { dg-final { scan-tree-dump "return 1;" "optimized"} } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr110539-2.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-2.c
> new file mode 100644
> index 00000000000..17874d349ef
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-2.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fdump-tree-optimized" } */
> +int f(int a)
> +{
> + int b = a & 1;
> + int c = b == 0;
> + return c == b;
> +}
> +
> +/* This should be optimized to just return 0; */
> +/* { dg-final { scan-tree-dump-not " == " "optimized"} } */
> +/* { dg-final { scan-tree-dump "return 0;" "optimized"} } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr110539-3.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-3.c
> new file mode 100644
> index 00000000000..c8ef6f56dcd
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr110539-3.c
> @@ -0,0 +1,70 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +void foo(void);
> +static int a, c = 1;
> +static short b;
> +static int *d = &c, *e = &a;
> +static int **f = &d;
> +void __assert_fail() __attribute__((__noreturn__));
> +static void g(short h) {
> + if (*d)
> + ;
> + else {
> + if (e) __assert_fail();
> + if (a) {
> + __builtin_unreachable();
> + } else
> + __assert_fail();
> + }
> + if ((((0, 0) || h) == h) + b) *f = 0;
> +}
> +int main() {
> + int i = 0 != 10 & a;
> + g(i);
> + *e = 9;
> + e = 0;
> + if (d == 0)
> + ;
> + else
> + foo();
> + ;
> +}
> +/* The call to foo should be optimized away. */
> +/* The missed optimization at -O2 here was:
> + int b = a & 1;
> + int c = b != 0;
> + int d = c == b;
> + not being optimized to 1 early enough, it is done in vrp2 but
> + that is too late.
> + In phiopt2 we got:
> + _17 = i_7 != 0;
> + _12 = (int) _17;
> + if (i_7 == _12)
> + goto <bb 9>; [50.00%]
> + else
> + goto <bb 10>; [50.00%]
> +
> + <bb 9> [local count: 268435456]:
> + d = 0B;
> +
> + <bb 10> [local count: 536870913]:
> + e.1_3 = e;
> + *e.1_3 = 9;
> + e = 0B;
> + d.2_4 = d;
> + if (d.2_4 == 0B)
> +
> + The first if is not optimized before, until vrp2 which is
> + too late as there are no passes which will then find the
> + load of d in `d.2_4 = d;` was `0B` after vrp2.
> +
> + Now we optimize dom2 because phiopt2 we just get:
> + _12 = i_7;
> + if (i_7 == _12)
> + goto <bb 9>; [50.00%]
> + else
> + goto <bb 10>; [50.00%]
> + */
> +
> +/* { dg-final { scan-tree-dump-not "foo \\(\\)" "optimized"} } */
> --
> 2.31.1
>
