On Sat, Nov 2, 2024 at 4:10 PM Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> Sometimes we get back a full ssa name when looking up the comparison of the
> GIMPLE_COND
> rather than a predicate. We then want to lookup the `val != 0` for the
> predicate.
>
> Note this might happen with other boolean assignments and COND_EXPR but I am
> not sure
> if it is as important; I have not found a testcase yet.
>
> Bootstrapped and tested on x86_64-linux-gnu.
OK.
Thanks,
Richard.
> PR tree-optimization/117414
>
> gcc/ChangeLog:
>
> * tree-ssa-sccvn.cc (process_bb): Lookup
> `val != 0` if got back a ssa name when looking the comparison.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/fre-predicated-4.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> .../gcc.dg/tree-ssa/fre-predicated-4.c | 38 +++++++++++++++++++
> gcc/tree-ssa-sccvn.cc | 10 +++++
> 2 files changed, 48 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-4.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-4.c
> b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-4.c
> new file mode 100644
> index 00000000000..fe9d2e2fb58
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-4.c
> @@ -0,0 +1,38 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +/* PR tree-optimization/117414 */
> +
> +/* Fre1 should figure out that `*aaa != 0`
> + For f0 and f1. */
> +
> +
> +void foo();
> +int f0(int *aaa, int j, int t)
> +{
> + int b = *aaa;
> + if (b == 0 || t == 1)
> + return 0;
> + for(int i = 0; i < j; i++)
> + {
> + if (!*aaa) foo();
> + }
> + return 0;
> +}
> +
> +int f1(int *aaa, int j, int t)
> +{
> + int b = *aaa;
> + if (b == 0)
> + return 0;
> + if (t == 1)
> + return 0;
> + for(int i = 0; i < j; i++)
> + {
> + if (!*aaa) foo();
> + }
> + return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
> +/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
> diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
> index 190b7d24f1a..c8d40697560 100644
> --- a/gcc/tree-ssa-sccvn.cc
> +++ b/gcc/tree-ssa-sccvn.cc
> @@ -8149,6 +8149,16 @@ process_bb (rpo_elim &avail, basic_block bb,
> val = vn_nary_op_lookup_pieces (2, gimple_cond_code (last),
> boolean_type_node, ops,
> &vnresult);
> + /* Got back a ssa name, then try looking up `val != 0`
> + as it might have been recorded that way. */
> + if (val && TREE_CODE (val) == SSA_NAME)
> + {
> + ops[0] = val;
> + ops[1] = build_zero_cst (TREE_TYPE (val));
> + val = vn_nary_op_lookup_pieces (2, NE_EXPR,
> + boolean_type_node, ops,
> + &vnresult);
> + }
> /* Did we get a predicated value? */
> if (! val && vnresult && vnresult->predicated_values)
> {
> --
> 2.43.0
>
