On Thu, Aug 3, 2023 at 4:34 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> So I didn't expect valueization to cause calling gimple_nop_convert
> to iterate between 2 different SSA names causing an infinite loop
> in gimple_bitwise_inverted_equal_p.
> So we should cause a bound on gimple_bitwise_inverted_equal_p calling
> gimple_nop_convert and only look through one rather than always.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
> PR tree-optimization/110874
> * gimple-match-head.cc (gimple_bitwise_inverted_equal_p):
> Add new argument, again with default value of true.
> Don't try gimple_nop_convert if again is false.
> Update call to gimple_bitwise_inverted_equal_p for
> new argument.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/110874
> * gcc.c-torture/compile/pr110874-a.c: New test.
> ---
> gcc/gimple-match-head.cc | 14 +++++++++-----
> .../gcc.c-torture/compile/pr110874-a.c | 17 +++++++++++++++++
> 2 files changed, 26 insertions(+), 5 deletions(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
>
> diff --git a/gcc/gimple-match-head.cc b/gcc/gimple-match-head.cc
> index b1e96304d7c..e91aaab86dd 100644
> --- a/gcc/gimple-match-head.cc
> +++ b/gcc/gimple-match-head.cc
> @@ -273,7 +273,7 @@ gimple_bitwise_equal_p (tree expr1, tree expr2, tree
> (*valueize) (tree))
> /* Helper function for bitwise_equal_p macro. */
>
> static inline bool
> -gimple_bitwise_inverted_equal_p (tree expr1, tree expr2, tree (*valueize)
> (tree))
> +gimple_bitwise_inverted_equal_p (tree expr1, tree expr2, tree (*valueize)
> (tree), bool again = true)
> {
> if (expr1 == expr2)
> return false;
> @@ -285,12 +285,16 @@ gimple_bitwise_inverted_equal_p (tree expr1, tree
> expr2, tree (*valueize) (tree)
> return false;
>
> tree other;
> - if (gimple_nop_convert (expr1, &other, valueize)
> - && gimple_bitwise_inverted_equal_p (other, expr2, valueize))
> + if (again
> + && gimple_nop_convert (expr1, &other, valueize)
> + && other != expr1
> + && gimple_bitwise_inverted_equal_p (other, expr2, valueize, false))
> return true;
>
> - if (gimple_nop_convert (expr2, &other, valueize)
> - && gimple_bitwise_inverted_equal_p (expr1, other, valueize))
> + if (again
> + && gimple_nop_convert (expr2, &other, valueize)
> + && other != expr2
> + && gimple_bitwise_inverted_equal_p (expr1, other, valueize, false))
> return true;
Hmm, I don't think this tests all three relevant combinations? I think the way
gimple_bitwise_equal_p handles this is better (not recursing). I'd split out
the "tail" matching the BIT_NOT to another helper, I suppose that could
even be a (match ...) pattern here.
> if (TREE_CODE (expr1) != SSA_NAME
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
> b/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
> new file mode 100644
> index 00000000000..b314410a892
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
> @@ -0,0 +1,17 @@
> +struct S1 {
> + unsigned f0;
> +};
> +static int g_161;
> +void func_109(unsigned g_227, unsigned t) {
> + struct S1 l_178;
> + int l_160 = 0x1FAE99D5L;
> + int *l_230[] = {&l_160};
> + if (l_160) {
> + for (l_178.f0 = -7; l_178.f0;) {
> + ++g_227;
> + break;
> + }
> + (g_161) = g_227;
> + }
> + (g_161) &= t;
> +}
> --
> 2.31.1
>
