On Fri, 12 Jan 2024, Jakub Jelinek wrote:
> Hi!
>
> For INTEGER_CST operands, the code decides if it should emit the whole
> INTEGER_CST into memory, or if there are enough upper bits either all 0s
> or all 1s to warrant an optimization, where we use memory for lower limbs
> or even just an INTEGER_CST for least significant limb and fill in the
> rest of limbs with 0s or 1s. Unfortunately when not using
> bitint_min_cst_precision, the code was using tree_int_cst_sgn (op) < 0
> to determine whether to fill in the upper bits with 1s or 0s. That is
> incorrect for TYPE_UNSIGNED INTEGER_CSTs which have higher limbs full of
> ones, we really want to check here whether the most significant bit is
> set or clear.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
OK.
> 2024-01-12 Jakub Jelinek
>
> PR tree-optimization/113334
> * gimple-lower-bitint.cc (bitint_large_huge::handle_operand): Use
> wi::neg_p (wi::to_wide (op)) instead of tree_int_cst_sgn (op) < 0
> to determine if number should be extended by all ones rather than zero
> extended.
>
> * gcc.dg/torture/bitint-46.c: New test.
>
> --- gcc/gimple-lower-bitint.cc.jj 2024-01-11 14:27:26.0 +0100
> +++ gcc/gimple-lower-bitint.cc2024-01-11 17:35:07.484557476 +0100
> @@ -997,7 +997,7 @@ bitint_large_huge::handle_operand (tree
> {
> unsigned int prec = TYPE_PRECISION (TREE_TYPE (op));
> unsigned rem = prec % (2 * limb_prec);
> - int ext = tree_int_cst_sgn (op) < 0 ? -1 : 0;
> + int ext = wi::neg_p (wi::to_wide (op)) ? -1 : 0;
> tree c = m_data[m_data_cnt];
> unsigned min_prec = TYPE_PRECISION (TREE_TYPE (c));
> g = gimple_build_cond (LT_EXPR, idx,
> --- gcc/testsuite/gcc.dg/torture/bitint-46.c.jj 2024-01-11
> 17:44:42.360409112 +0100
> +++ gcc/testsuite/gcc.dg/torture/bitint-46.c 2024-01-11 17:44:31.471564635
> +0100
> @@ -0,0 +1,32 @@
> +/* PR tree-optimization/113334 */
> +/* { dg-do run { target bitint } } */
> +/* { dg-options "-std=c23 -pedantic-errors" } */
> +/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */
> +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
> +
> +#if __BITINT_MAXWIDTH__ >= 384
> +__attribute__((noipa)) _BitInt(384)
> +foo (int s)
> +{
> + _BitInt(384) z = (-(unsigned _BitInt(384)) 4) >> s;
> + return z;
> +}
> +#endif
> +
> +int
> +main ()
> +{
> +#if __BITINT_MAXWIDTH__ >= 384
> + if (foo (59) !=
> 0x1fwb)
> +__builtin_abort ();
> + if (foo (0) != -4wb)
> +__builtin_abort ();
> + if (foo (1) !=
> 0x7ffewb)
> +__builtin_abort ();
> + if (foo (11) !=
> 0x001fwb)
> +__builtin_abort ();
> + if (foo (123) !=
> 0x1fwb)
> +__builtin_abort ();
> +#endif
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
