On Thu, Nov 27, 2025 at 11:27 AM Robin Dapp <[email protected]> wrote:
>
> Hi,
>
> This fixes up r16-5561-g283eb27d5f674b where I allowed nop conversions
> for the input operands. There are several paths through the function
> that still require an explicit nop conversion for them. This patch adds
> them. I hope to have caught everything but I don't find variable naming
> particularly descriptive with op, ref, orig and implicit control flow
> depending on orig. I refactored it locally but guess that's rather
> stage 1 material as the diff is complicated due to renaming.
>
> Bootstrapped on x86 and power10. Regtested on riscv64 and aarch64.
OK.
> Regards
> Robin
>
> PR tree-optimization/122855
> PR tree-optimization/122850
>
> gcc/ChangeLog:
>
> * tree-ssa-forwprop.cc (simplify_vector_constructor): Nop
> convert input if necessary.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/pr122850.c: New test.
> * gcc.dg/vect/pr122855.c: New test.
> ---
> gcc/testsuite/gcc.dg/vect/pr122850.c | 13 ++++++++
> gcc/testsuite/gcc.dg/vect/pr122855.c | 15 +++++++++
> gcc/tree-ssa-forwprop.cc | 47 +++++++++++++++++++++++-----
> 3 files changed, 67 insertions(+), 8 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/pr122850.c
> create mode 100644 gcc/testsuite/gcc.dg/vect/pr122855.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/pr122850.c
> b/gcc/testsuite/gcc.dg/vect/pr122850.c
> new file mode 100644
> index 00000000000..4f50aa9660d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr122850.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile { target { x86_64-*-* i?86-*-* } } } */
> +/* { dg-additional-options "-O3 -march=haswell -m32" } */
> +
> +typedef int v2ll __attribute__ ((__vector_size__ (2 * sizeof (int))));
> +typedef unsigned int v2ull __attribute__ ((__vector_size__ (2 * sizeof
> (int))));
> +typedef __attribute__ ((__vector_size__ (2 * sizeof (short)))) short v2s;
> +
> +v2ll
> +f (v2ull e)
> +{
> + v2s c = (v2s) e[0];
> + return (v2ll) {(int) c, 0};
> +}
> diff --git a/gcc/testsuite/gcc.dg/vect/pr122855.c
> b/gcc/testsuite/gcc.dg/vect/pr122855.c
> new file mode 100644
> index 00000000000..3084d2062a1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr122855.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target { x86_64-*-* i?86-*-* } } } */
> +/* { dg-additional-options "-O3 -march=haswell" } */
> +
> +int zoom_x3_weights_0, zoom_x3_j, zoom_x3_pixel2;
> +
> +void zoom_x3(char *__restrict s, char *__restrict zoom_x3_tmp) {
> + int pixel0 = 0, pixel1 = 0;
> + for (; zoom_x3_j; zoom_x3_j--) {
> + pixel0 += *s++ * zoom_x3_weights_0;
> + pixel1 += *s++ * zoom_x3_weights_0;
> + zoom_x3_pixel2 += *s++ * zoom_x3_weights_0;
> + }
> + *zoom_x3_tmp++ = pixel0 < 0 ? 0 : pixel0 > 255 ? 255 : pixel0;
> + *zoom_x3_tmp = pixel1 < 0 ? 0 : pixel1 > 255 ? 255 : pixel1;
> +}
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index 00140ce950c..2200fc04918 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -4183,24 +4183,45 @@ simplify_vector_constructor (gimple_stmt_iterator
> *gsi)
> /* ??? We can see if we can safely convert to the original
> element type. */
> converted_orig1 = conv_code != ERROR_MARK;
> + tree target_type = converted_orig1 ? type : perm_type;
> + tree nonconstant_for_splat = one_nonconstant;
> + /* If there's a nop conversion between the target element type and
> + the nonconstant's type, convert it. */
> + if (!useless_type_conversion_p (TREE_TYPE (target_type),
> + TREE_TYPE (one_nonconstant)))
> + nonconstant_for_splat
> + = gimple_build (&stmts, NOP_EXPR, TREE_TYPE (target_type),
> + one_nonconstant);
> orig[1] = gimple_build_vector_from_val (&stmts, UNKNOWN_LOCATION,
> - converted_orig1
> - ? type : perm_type,
> - one_nonconstant);
> + target_type,
> + nonconstant_for_splat);
> }
> else if (orig[1] == error_mark_node)
> {
> /* ??? See if we can convert the vector to the original type. */
> converted_orig1 = conv_code != ERROR_MARK;
> unsigned n = converted_orig1 ? nelts : refnelts;
> - tree_vector_builder vec (converted_orig1
> - ? type : perm_type, n, 1);
> + tree target_type = converted_orig1 ? type : perm_type;
> + tree_vector_builder vec (target_type, n, 1);
> for (unsigned i = 0; i < n; ++i)
> if (i < nelts && constants[i])
> - vec.quick_push (constants[i]);
> + {
> + tree constant = constants[i];
> + /* If there's a nop conversion, convert the constant. */
> + if (!useless_type_conversion_p (TREE_TYPE (target_type),
> + TREE_TYPE (constant)))
> + constant = fold_convert (TREE_TYPE (target_type), constant);
> + vec.quick_push (constant);
> + }
> else
> - /* ??? Push a don't-care value. */
> - vec.quick_push (one_constant);
> + {
> + /* ??? Push a don't-care value. */
> + tree constant = one_constant;
> + if (!useless_type_conversion_p (TREE_TYPE (target_type),
> + TREE_TYPE (constant)))
> + constant = fold_convert (TREE_TYPE (target_type), constant);
> + vec.quick_push (constant);
> + }
> orig[1] = vec.build ();
> }
> tree blend_op2 = NULL_TREE;
> @@ -4224,6 +4245,16 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
> return false;
> blend_op2 = vec_perm_indices_to_tree (mask_type, indices);
> }
> +
> + /* For a real orig[1] (no splat, constant etc.) we might need to
> + nop-convert it. Do so here. */
> + if (orig[1] && orig[1] != error_mark_node
> + && !useless_type_conversion_p (perm_type, TREE_TYPE (orig[1]))
> + && tree_nop_conversion_p (TREE_TYPE (perm_type),
> + TREE_TYPE (TREE_TYPE (orig[1]))))
> + orig[1] = gimple_build (&stmts, VIEW_CONVERT_EXPR, perm_type,
> + orig[1]);
> +
> tree orig1_for_perm
> = converted_orig1 ? build_zero_cst (perm_type) : orig[1];
> tree res = gimple_build (&stmts, VEC_PERM_EXPR, perm_type,
> --
> 2.51.1
>
