On Thu, Aug 24, 2023 at 4:39 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> For 1bit types, negate is either undefined or don't change the value.
> In either cases we want to remove them.
> This patch adds a match pattern to do that.
> Also converting to a 1bit type we can remove the negate just like we already
> do
> for `&1` so this patch adds that too.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
OK.
Thanks,
Richard.
> Notes on the testcases:
> This patch is the last part to fix PR 95929; cond-bool-2.c testcase.
> bit1neg-1.c is a 1bit-field testcase where we could remove the assignment
> all the way in one case (which happened on the RTL level for some targets but
> not all).
> cond-bool-2.c is the reduced testcase of PR 95929.
>
> PR tree-optimization/95929
>
> gcc/ChangeLog:
>
> * match.pd (convert?(-a)): New pattern
> for 1bit integer types.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/bit1neg-1.c: New test.
> * gcc.dg/tree-ssa/cond-bool-1.c: New test.
> * gcc.dg/tree-ssa/cond-bool-2.c: New test.
> ---
> gcc/match.pd | 12 ++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c | 23 ++++++++++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c | 21 +++++++++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c | 26 +++++++++++++++++++++
> 4 files changed, 82 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index a2e56d5a4e8..3bbeceb37b4 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -9090,6 +9090,18 @@ and,
> (if (!TYPE_OVERFLOW_SANITIZED (type))
> (bit_and @0 @1)))
>
> +/* `-a` is just `a` if the type is 1bit wide or when converting
> + to a 1bit type; similar to the above transformation of `(-x)&1`.
> + This is used mostly with the transformation of
> + `a ? ~b : b` into `(-a)^b`.
> + It also can show up with bitfields. */
> +(simplify
> + (convert? (negate @0))
> + (if (INTEGRAL_TYPE_P (type)
> + && TYPE_PRECISION (type) == 1
> + && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0)))
> + (convert @0)))
> +
> /* Optimize
> c1 = VEC_PERM_EXPR (a, a, mask)
> c2 = VEC_PERM_EXPR (b, b, mask)
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
> new file mode 100644
> index 00000000000..2f123fbb9b5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +struct f
> +{
> + int a:1;
> +};
> +
> +void g(struct f *a)
> +{
> + int t = a->a;
> + t = -t;
> + a->a = t;
> +}
> +void g1(struct f *a, int b)
> +{
> + int t = b;
> + t = -t;
> + a->a = t;
> +}
> +/* the 2 negates should have been removed as this is basically the same
> + as (-a) & 1. */
> +/* { dg-final { scan-tree-dump-not " = -" "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
> new file mode 100644
> index 00000000000..752a3030ad1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +_Bool f1(int a, int b)
> +{
> + _Bool _1 = b != 0;
> + _Bool _2 = a != 0;
> + _Bool _8 = a == 0;
> + _Bool _13;
> + if (_1) _13 = _8; else _13 = _2;
> + return _13;
> +}
> +
> +/* We should be able to optimize this to (a != 0) ^ (b != 0) */
> +/* There should be no negate_expr nor gimple_cond here. */
> +
> +/* { dg-final { scan-tree-dump-not "negate_expr, " "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "ne_expr, " 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "gimple_cond " "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "gimple_phi " "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "bit_xor_expr, " 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_assign " 3 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
> b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
> new file mode 100644
> index 00000000000..b3e7e25dec6
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
> @@ -0,0 +1,26 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +
> +/* PR tree-optimization/95929 */
> +
> +
> +static inline _Bool nand(_Bool a, _Bool b)
> +{
> + return !(a && b);
> +}
> +
> +_Bool f(int a, int b)
> +{
> + return nand(nand(b, nand(a, a)), nand(a, nand(b, b)));
> +}
> +
> +/* We should be able to optimize this to (a != 0) ^ (b != 0) */
> +/* There should be no negate_expr nor gimple_cond here. */
> +
> +/* { dg-final { scan-tree-dump-not "negate_expr, " "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "ne_expr, " 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "gimple_cond " "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "cond_expr, " "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "gimple_phi " "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "bit_xor_expr, " 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_assign " 3 "optimized" } } */
> --
> 2.31.1
>
