On Wed, Mar 31, 2021 at 12:24 PM Richard Sandiford via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This PR is caused by POLY_INT_CSTs being (necessarily) valid
> in tree-level VECTOR_CSTs but CONST_POLY_INTs not being valid
> in RTL CONST_VECTORs. I can't tell/remember how deliberate
> that was, but I'm guessing not very. In particular,
> valid_for_const_vector_p was added to guard against symbolic
> constants rather than CONST_POLY_INTs.
>
> I did briefly consider whether we should maintain the current
> status anyway. However, that would then require a way of
> constructing variable-length vectors from individiual elements
> if, say, we have:
>
> { [2, 2], [3, 2], [4, 2], … }
>
> So I'm chalking this up to an oversight. I think the intention
> (and certainly the natural thing) is to have the same rules for
> both trees and RTL.
>
> The SVE CONST_VECTOR code should already be set up to handle
> CONST_POLY_INTs. However, we need to add support for Advanced SIMD
> CONST_VECTORs that happen to contain SVE-based values. The patch does
> that by expanding such CONST_VECTORs in the same way as variable vectors.
>
> Tested on aarch64-linux-gnu, armeb-eabi and x86_64-linux-gnu.
> OK for the target-independent bits?
OK.
Richard.
> Richard
>
>
> gcc/
> PR rtl-optimization/97141
> PR rtl-optimization/98726
> * emit-rtl.c (valid_for_const_vector_p): Return true for
> CONST_POLY_INT_P.
> * rtx-vector-builder.h (rtx_vector_builder::step): Return a
> poly_wide_int instead of a wide_int.
> (rtx_vector_builder::apply_set): Take a poly_wide_int instead
> of a wide_int.
> * rtx-vector-builder.c (rtx_vector_builder::apply_set): Likewise.
> * config/aarch64/aarch64.c (aarch64_legitimate_constant_p): Return
> false for CONST_VECTORs that cannot be forced to memory.
> * config/aarch64/aarch64-simd.md (mov<mode>): If a CONST_VECTOR
> is too complex to force to memory, build it up from individual
> elements instead.
>
> gcc/testsuite/
> PR rtl-optimization/97141
> PR rtl-optimization/98726
> * gcc.c-torture/compile/pr97141.c: New test.
> * gcc.c-torture/compile/pr98726.c: Likewise.
> * gcc.target/aarch64/sve/pr97141.c: Likewise.
> * gcc.target/aarch64/sve/pr98726.c: Likewise.
> ---
> gcc/config/aarch64/aarch64-simd.md | 11 +++++++++
> gcc/config/aarch64/aarch64.c | 24 +++++++++++--------
> gcc/emit-rtl.c | 1 +
> gcc/rtx-vector-builder.c | 6 ++---
> gcc/rtx-vector-builder.h | 10 ++++----
> gcc/testsuite/gcc.c-torture/compile/pr97141.c | 8 +++++++
> gcc/testsuite/gcc.c-torture/compile/pr98726.c | 7 ++++++
> .../gcc.target/aarch64/sve/pr97141.c | 10 ++++++++
> .../gcc.target/aarch64/sve/pr98726.c | 9 +++++++
> 9 files changed, 68 insertions(+), 18 deletions(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr97141.c
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr98726.c
> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr97141.c
> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr98726.c
>
> diff --git a/gcc/config/aarch64/aarch64-simd.md
> b/gcc/config/aarch64/aarch64-simd.md
> index d86e8e72f18..4edee99051c 100644
> --- a/gcc/config/aarch64/aarch64-simd.md
> +++ b/gcc/config/aarch64/aarch64-simd.md
> @@ -35,6 +35,17 @@ (define_expand "mov<mode>"
> && aarch64_mem_pair_operand (operands[0], DImode))
> || known_eq (GET_MODE_SIZE (<MODE>mode), 8))))
> operands[1] = force_reg (<MODE>mode, operands[1]);
> +
> + /* If a constant is too complex to force to memory (e.g. because it
> + contains CONST_POLY_INTs), build it up from individual elements instead.
> + We should only need to do this before RA; aarch64_legitimate_constant_p
> + should ensure that we don't try to rematerialize the constant later. */
> + if (GET_CODE (operands[1]) == CONST_VECTOR
> + && targetm.cannot_force_const_mem (<MODE>mode, operands[1]))
> + {
> + aarch64_expand_vector_init (operands[0], operands[1]);
> + DONE;
> + }
> "
> )
>
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index 5eda9e80bd0..77573e96820 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -17925,10 +17925,22 @@ aarch64_legitimate_constant_p (machine_mode mode,
> rtx x)
> {
> /* Support CSE and rematerialization of common constants. */
> if (CONST_INT_P (x)
> - || (CONST_DOUBLE_P (x) && GET_MODE_CLASS (mode) == MODE_FLOAT)
> - || GET_CODE (x) == CONST_VECTOR)
> + || (CONST_DOUBLE_P (x) && GET_MODE_CLASS (mode) == MODE_FLOAT))
> return true;
>
> + /* Only accept variable-length vector constants if they can be
> + handled directly.
> +
> + ??? It would be possible (but complex) to handle rematerialization
> + of other constants via secondary reloads. */
> + if (!GET_MODE_SIZE (mode).is_constant ())
> + return aarch64_simd_valid_immediate (x, NULL);
> +
> + /* Otherwise, accept any CONST_VECTOR that, if all else fails, can at
> + least be forced to memory and loaded from there. */
> + if (GET_CODE (x) == CONST_VECTOR)
> + return !targetm.cannot_force_const_mem (mode, x);
> +
> /* Do not allow vector struct mode constants for Advanced SIMD.
> We could support 0 and -1 easily, but they need support in
> aarch64-simd.md. */
> @@ -17936,14 +17948,6 @@ aarch64_legitimate_constant_p (machine_mode mode,
> rtx x)
> if (vec_flags == (VEC_ADVSIMD | VEC_STRUCT))
> return false;
>
> - /* Only accept variable-length vector constants if they can be
> - handled directly.
> -
> - ??? It would be possible to handle rematerialization of other
> - constants via secondary reloads. */
> - if (vec_flags & VEC_ANY_SVE)
> - return aarch64_simd_valid_immediate (x, NULL);
> -
> if (GET_CODE (x) == HIGH)
> x = XEXP (x, 0);
>
> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
> index b23284e5e56..1113c58c49e 100644
> --- a/gcc/emit-rtl.c
> +++ b/gcc/emit-rtl.c
> @@ -5949,6 +5949,7 @@ bool
> valid_for_const_vector_p (machine_mode, rtx x)
> {
> return (CONST_SCALAR_INT_P (x)
> + || CONST_POLY_INT_P (x)
> || CONST_DOUBLE_AS_FLOAT_P (x)
> || CONST_FIXED_P (x));
> }
> diff --git a/gcc/rtx-vector-builder.c b/gcc/rtx-vector-builder.c
> index 58b3e10a14a..cf9b3dd1af9 100644
> --- a/gcc/rtx-vector-builder.c
> +++ b/gcc/rtx-vector-builder.c
> @@ -46,11 +46,11 @@ rtx_vector_builder::build (rtvec v)
>
> rtx
> rtx_vector_builder::apply_step (rtx base, unsigned int factor,
> - const wide_int &step) const
> + const poly_wide_int &step) const
> {
> scalar_int_mode int_mode = as_a <scalar_int_mode> (GET_MODE_INNER
> (m_mode));
> - return immed_wide_int_const (wi::add (rtx_mode_t (base, int_mode),
> - factor * step),
> + return immed_wide_int_const (wi::to_poly_wide (base, int_mode)
> + + factor * step,
> int_mode);
> }
>
> diff --git a/gcc/rtx-vector-builder.h b/gcc/rtx-vector-builder.h
> index ea32208b30a..30a91e80b40 100644
> --- a/gcc/rtx-vector-builder.h
> +++ b/gcc/rtx-vector-builder.h
> @@ -44,8 +44,8 @@ private:
> bool equal_p (rtx, rtx) const;
> bool allow_steps_p () const;
> bool integral_p (rtx) const;
> - wide_int step (rtx, rtx) const;
> - rtx apply_step (rtx, unsigned int, const wide_int &) const;
> + poly_wide_int step (rtx, rtx) const;
> + rtx apply_step (rtx, unsigned int, const poly_wide_int &) const;
> bool can_elide_p (rtx) const { return true; }
> void note_representative (rtx *, rtx) {}
>
> @@ -115,11 +115,11 @@ rtx_vector_builder::integral_p (rtx elt) const
> /* Return the value of element ELT2 minus the value of element ELT1.
> Both elements are known to be CONST_SCALAR_INT_Ps. */
>
> -inline wide_int
> +inline poly_wide_int
> rtx_vector_builder::step (rtx elt1, rtx elt2) const
> {
> - return wi::sub (rtx_mode_t (elt2, GET_MODE_INNER (m_mode)),
> - rtx_mode_t (elt1, GET_MODE_INNER (m_mode)));
> + return (wi::to_poly_wide (elt2, GET_MODE_INNER (m_mode))
> + - wi::to_poly_wide (elt1, GET_MODE_INNER (m_mode)));
> }
>
> #endif
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr97141.c
> b/gcc/testsuite/gcc.c-torture/compile/pr97141.c
> new file mode 100644
> index 00000000000..1a9ff830a22
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr97141.c
> @@ -0,0 +1,8 @@
> +int a;
> +short b, c;
> +short d(short e, short f) { return e + f; }
> +void g(void) {
> + a = -9;
> + for (; a != 51; a = d(a, 5))
> + b |= c;
> +}
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr98726.c
> b/gcc/testsuite/gcc.c-torture/compile/pr98726.c
> new file mode 100644
> index 00000000000..ce24b18ce55
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr98726.c
> @@ -0,0 +1,7 @@
> +int a, c;
> +char b;
> +int d() {
> + a = 0;
> + for (; a <= 21; a = (short)a + 1)
> + b &= c;
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr97141.c
> b/gcc/testsuite/gcc.target/aarch64/sve/pr97141.c
> new file mode 100644
> index 00000000000..942e4a48d91
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr97141.c
> @@ -0,0 +1,10 @@
> +/* { dg-options "-O3" } */
> +
> +int a;
> +short b, c;
> +short d(short e, short f) { return e + f; }
> +void g(void) {
> + a = -9;
> + for (; a != 51; a = d(a, 5))
> + b |= c;
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr98726.c
> b/gcc/testsuite/gcc.target/aarch64/sve/pr98726.c
> new file mode 100644
> index 00000000000..2395cab57e5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr98726.c
> @@ -0,0 +1,9 @@
> +/* { dg-options "-O3" } */
> +
> +int a, c;
> +char b;
> +int d() {
> + a = 0;
> + for (; a <= 21; a = (short)a + 1)
> + b &= c;
> +}
