On Thu, 4 Jan 2024, Jakub Jelinek wrote:
> Hi!
>
> The PHI argument expansion of INTEGER_CSTs where bitint_min_cst_precision
> returns significantly smaller precision than the PHI result precision is
> optimized by loading the much smaller constant (if any) from memory and
> then either setting the remaining limbs to {} or calling memset with -1.
> The case where no constant is loaded (i.e. c == NULL) is when the
> INTEGER_CST is 0 or all_ones - in that case we can just set all the limbs
> to {} or call memset with -1 on everything.
> While for the all ones extension case that is what the code was already
> doing, I missed one spot in the zero extension case, where constricting
> the offset of the MEM_REF lhs of the = {} store it was using unconditionally
> the byte size of c, which obviously doesn't work if c is NULL. In that case
> we want to use zero offset.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
OK.
Richard.
> 2024-01-04 Jakub Jelinek <[email protected]>
>
> PR tree-optimization/113120
> * gimple-lower-bitint.cc (gimple_lower_bitint): Fix handling of very
> large _BitInt zero INTEGER_CST PHI argument.
>
> * gcc.dg/bitint-62.c: New test.
>
> --- gcc/gimple-lower-bitint.cc.jj 2024-01-03 11:51:27.000000000 +0100
> +++ gcc/gimple-lower-bitint.cc 2024-01-03 13:53:30.699328045 +0100
> @@ -6582,8 +6582,12 @@ gimple_lower_bitint (void)
> = build_array_type_nelts (large_huge.m_limb_type,
> nelts);
> tree ptype = build_pointer_type (TREE_TYPE (v1));
> - tree off = fold_convert (ptype,
> - TYPE_SIZE_UNIT (TREE_TYPE (c)));
> + tree off;
> + if (c)
> + off = fold_convert (ptype,
> + TYPE_SIZE_UNIT (TREE_TYPE (c)));
> + else
> + off = build_zero_cst (ptype);
> tree vd = build2 (MEM_REF, vtype,
> build_fold_addr_expr (v1), off);
> g = gimple_build_assign (vd, build_zero_cst (vtype));
> --- gcc/testsuite/gcc.dg/bitint-62.c.jj 2024-01-03 14:11:22.332301884
> +0100
> +++ gcc/testsuite/gcc.dg/bitint-62.c 2024-01-03 14:10:58.219640178 +0100
> @@ -0,0 +1,32 @@
> +/* PR tree-optimization/113120 */
> +/* { dg-do compile { target bitint } } */
> +/* { dg-options "-std=c23 -O2" } */
> +
> +_BitInt(8) a;
> +_BitInt(55) b;
> +
> +#if __BITINT_MAXWIDTH__ >= 401
> +static __attribute__((noinline, noclone)) void
> +foo (unsigned _BitInt(1) c, _BitInt(401) d)
> +{
> + c /= d << b;
> + a = c;
> +}
> +
> +void
> +bar (void)
> +{
> + foo (1, 4);
> +}
> +#endif
> +
> +#if __BITINT_MAXWIDTH__ >= 6928
> +_BitInt(6928)
> +baz (int x, _BitInt(6928) y)
> +{
> + if (x)
> + return y;
> + else
> + return 0;
> +}
> +#endif
>
> Jakub
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
