On Fri, Oct 20, 2023 at 4:21 AM liuhongt <hongtao....@intel.com> wrote:
>
> >So with pow being available this limit shouldn't be necessary any more and
> >the testcase adjustment can be avoided?
> I tries, compile time still hogs on mpz_powm(3, INT_MAX), so i'll just
> keep this.
Doh :/ Maybe it's possible to limit the output precision for mpz computes
somehow? I suspect we're really computing the very large resulting number
here ... unfortunately I don't know GMP enough to tell.
> >and to avoid undefined behavior with too large shift just go the gmp
> >way unconditionally.
> Changed.
>
> >this comment is now resolved I think.
> Removed.
>
> >mpz_pow_ui uses unsigned long while i think we constrain known niters
> >to uint64 - so I suggest to use mpz_powm instead (limiting to a possibly
> >host specific limit - unsigned long - is unfortunately a no-go).
> Changed.
>
> There's loop in vect_peel_nonlinear_iv_init to get init_expr *
> pow (step_expr, skip_niters). When skipn_iters is too big, compile time
> hogs. To avoid that, optimize init_expr * pow (step_expr, skip_niters) to
> init_expr << (exact_log2 (step_expr) * skip_niters) when step_expr is
> pow of 2, otherwise give up vectorization when skip_niters >=
> TYPE_PRECISION (TREE_TYPE (init_expr)).
>
> Also give up vectorization when niters_skip is negative which will be
> used for fully masked loop.
>
> Bootstrapped and regtested on x86_64-linux-gnu{-m32,}.
> Ok for trunk.
OK.
Thanks,
Richard.
> gcc/ChangeLog:
>
> PR tree-optimization/111820
> PR tree-optimization/111833
> * tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p): Give
> up vectorization for nonlinear iv vect_step_op_mul when
> step_expr is not exact_log2 and niters is greater than
> TYPE_PRECISION (TREE_TYPE (step_expr)). Also don't vectorize
> for nagative niters_skip which will be used by fully masked
> loop.
> (vect_can_advance_ivs_p): Pass whole phi_info to
> vect_can_peel_nonlinear_iv_p.
> * tree-vect-loop.cc (vect_peel_nonlinear_iv_init): Optimize
> init_expr * pow (step_expr, skipn) to init_expr
> << (log2 (step_expr) * skipn) when step_expr is exact_log2.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/pr111820-1.c: New test.
> * gcc.target/i386/pr111820-2.c: New test.
> * gcc.target/i386/pr111820-3.c: New test.
> * gcc.target/i386/pr103144-mul-1.c: Adjust testcase.
> * gcc.target/i386/pr103144-mul-2.c: Adjust testcase.
> ---
> .../gcc.target/i386/pr103144-mul-1.c | 8 +++---
> .../gcc.target/i386/pr103144-mul-2.c | 8 +++---
> gcc/testsuite/gcc.target/i386/pr111820-1.c | 16 +++++++++++
> gcc/testsuite/gcc.target/i386/pr111820-2.c | 16 +++++++++++
> gcc/testsuite/gcc.target/i386/pr111820-3.c | 16 +++++++++++
> gcc/tree-vect-loop-manip.cc | 28 +++++++++++++++++--
> gcc/tree-vect-loop.cc | 13 ++++++---
> 7 files changed, 90 insertions(+), 15 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr111820-1.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr111820-2.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr111820-3.c
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
> b/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
> index 640c34fd959..913d7737dcd 100644
> --- a/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
> +++ b/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
> @@ -11,7 +11,7 @@ foo_mul (int* a, int b)
> for (int i = 0; i != N; i++)
> {
> a[i] = b;
> - b *= 3;
> + b *= 4;
> }
> }
>
> @@ -23,7 +23,7 @@ foo_mul_const (int* a)
> for (int i = 0; i != N; i++)
> {
> a[i] = b;
> - b *= 3;
> + b *= 4;
> }
> }
>
> @@ -34,7 +34,7 @@ foo_mul_peel (int* a, int b)
> for (int i = 0; i != 39; i++)
> {
> a[i] = b;
> - b *= 3;
> + b *= 4;
> }
> }
>
> @@ -46,6 +46,6 @@ foo_mul_peel_const (int* a)
> for (int i = 0; i != 39; i++)
> {
> a[i] = b;
> - b *= 3;
> + b *= 4;
> }
> }
> diff --git a/gcc/testsuite/gcc.target/i386/pr103144-mul-2.c
> b/gcc/testsuite/gcc.target/i386/pr103144-mul-2.c
> index 39fdea3a69d..b2ff186e335 100644
> --- a/gcc/testsuite/gcc.target/i386/pr103144-mul-2.c
> +++ b/gcc/testsuite/gcc.target/i386/pr103144-mul-2.c
> @@ -16,12 +16,12 @@ avx2_test (void)
>
> __builtin_memset (epi32_exp, 0, N * sizeof (int));
> int b = 8;
> - v8si init = __extension__(v8si) { b, b * 3, b * 9, b * 27, b * 81, b *
> 243, b * 729, b * 2187 };
> + v8si init = __extension__(v8si) { b, b * 4, b * 16, b * 64, b * 256, b *
> 1024, b * 4096, b * 16384 };
>
> for (int i = 0; i != N / 8; i++)
> {
> memcpy (epi32_exp + i * 8, &init, 32);
> - init *= 6561;
> + init *= 65536;
> }
>
> foo_mul (epi32_dst, b);
> @@ -32,11 +32,11 @@ avx2_test (void)
> if (__builtin_memcmp (epi32_dst, epi32_exp, 39 * 4) != 0)
> __builtin_abort ();
>
> - init = __extension__(v8si) { 1, 3, 9, 27, 81, 243, 729, 2187 };
> + init = __extension__(v8si) { 1, 4, 16, 64, 256, 1024, 4096, 16384 };
> for (int i = 0; i != N / 8; i++)
> {
> memcpy (epi32_exp + i * 8, &init, 32);
> - init *= 6561;
> + init *= 65536;
> }
>
> foo_mul_const (epi32_dst);
> diff --git a/gcc/testsuite/gcc.target/i386/pr111820-1.c
> b/gcc/testsuite/gcc.target/i386/pr111820-1.c
> new file mode 100644
> index 00000000000..50e960c39d4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr111820-1.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -mavx2 -fno-tree-vrp -Wno-aggressive-loop-optimizations
> -fdump-tree-vect-details" } */
> +/* { dg-final { scan-tree-dump "Avoid compile time hog on
> vect_peel_nonlinear_iv_init for nonlinear induction vec_step_op_mul when
> iteration count is too big" "vect" } } */
> +
> +int r;
> +int r_0;
> +
> +void f1 (void)
> +{
> + int n = 0;
> + while (-- n)
> + {
> + r_0 += r;
> + r *= 3;
> + }
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr111820-2.c
> b/gcc/testsuite/gcc.target/i386/pr111820-2.c
> new file mode 100644
> index 00000000000..dbeceb228c3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr111820-2.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -mavx2 -fno-tree-vrp -fdump-tree-vect-details
> -Wno-aggressive-loop-optimizations" } */
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> +
> +int r;
> +int r_0;
> +
> +void f (void)
> +{
> + int n = 0;
> + while (-- n)
> + {
> + r_0 += r ;
> + r *= 2;
> + }
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr111820-3.c
> b/gcc/testsuite/gcc.target/i386/pr111820-3.c
> new file mode 100644
> index 00000000000..b778f517663
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr111820-3.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -mavx2 -fno-tree-vrp -fdump-tree-vect-details
> -Wno-aggressive-loop-optimizations" } */
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> +
> +int r;
> +int r_0;
> +
> +void f (void)
> +{
> + int n = 14;
> + while (-- n)
> + {
> + r_0 += r ;
> + r *= 3;
> + }
> +}
> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> index 2608c286e5d..a530088b61d 100644
> --- a/gcc/tree-vect-loop-manip.cc
> +++ b/gcc/tree-vect-loop-manip.cc
> @@ -1783,8 +1783,10 @@ iv_phi_p (stmt_vec_info stmt_info)
> /* Return true if vectorizer can peel for nonlinear iv. */
> static bool
> vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
> - enum vect_induction_op_type induction_type)
> + stmt_vec_info stmt_info)
> {
> + enum vect_induction_op_type induction_type
> + = STMT_VINFO_LOOP_PHI_EVOLUTION_TYPE (stmt_info);
> tree niters_skip;
> /* Init_expr will be update by vect_update_ivs_after_vectorizer,
> if niters or vf is unkown:
> @@ -1805,11 +1807,31 @@ vect_can_peel_nonlinear_iv_p (loop_vec_info
> loop_vinfo,
> return false;
> }
>
> + /* Avoid compile time hog on vect_peel_nonlinear_iv_init. */
> + if (induction_type == vect_step_op_mul)
> + {
> + tree step_expr = STMT_VINFO_LOOP_PHI_EVOLUTION_PART (stmt_info);
> + tree type = TREE_TYPE (step_expr);
> +
> + if (wi::exact_log2 (wi::to_wide (step_expr)) == -1
> + && LOOP_VINFO_INT_NITERS(loop_vinfo) >= TYPE_PRECISION (type))
> + {
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> + "Avoid compile time hog on"
> + " vect_peel_nonlinear_iv_init"
> + " for nonlinear induction vec_step_op_mul"
> + " when iteration count is too big.\n");
> + return false;
> + }
> + }
> +
> /* Also doens't support peel for neg when niter is variable.
> ??? generate something like niter_expr & 1 ? init_expr : -init_expr? */
> niters_skip = LOOP_VINFO_MASK_SKIP_NITERS (loop_vinfo);
> if ((niters_skip != NULL_TREE
> - && TREE_CODE (niters_skip) != INTEGER_CST)
> + && (TREE_CODE (niters_skip) != INTEGER_CST
> + || (HOST_WIDE_INT) TREE_INT_CST_LOW (niters_skip) < 0))
> || (!vect_use_loop_mask_for_alignment_p (loop_vinfo)
> && LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) < 0))
> {
> @@ -1870,7 +1892,7 @@ vect_can_advance_ivs_p (loop_vec_info loop_vinfo)
> induction_type = STMT_VINFO_LOOP_PHI_EVOLUTION_TYPE (phi_info);
> if (induction_type != vect_step_op_add)
> {
> - if (!vect_can_peel_nonlinear_iv_p (loop_vinfo, induction_type))
> + if (!vect_can_peel_nonlinear_iv_p (loop_vinfo, phi_info))
> return false;
>
> continue;
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 89bdcaa0910..7a6bbff0c8f 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -9132,12 +9132,17 @@ vect_peel_nonlinear_iv_init (gimple_seq* stmts, tree
> init_expr,
> {
> tree utype = unsigned_type_for (type);
> init_expr = gimple_convert (stmts, utype, init_expr);
> - unsigned skipn = TREE_INT_CST_LOW (skip_niters);
> + wide_int skipn = wi::to_wide (skip_niters);
> wide_int begin = wi::to_wide (step_expr);
> - for (unsigned i = 0; i != skipn - 1; i++)
> - begin = wi::mul (begin, wi::to_wide (step_expr));
> + auto_mpz base, exp, mod, res;
> + wi::to_mpz (begin, base, TYPE_SIGN (type));
> + wi::to_mpz (skipn, exp, UNSIGNED);
> + mpz_ui_pow_ui (mod, 2, TYPE_PRECISION (type));
> + mpz_powm (res, base, exp, mod);
> + begin = wi::from_mpz (type, res, TYPE_SIGN (type));
> tree mult_expr = wide_int_to_tree (utype, begin);
> - init_expr = gimple_build (stmts, MULT_EXPR, utype, init_expr,
> mult_expr);
> + init_expr = gimple_build (stmts, MULT_EXPR, utype,
> + init_expr, mult_expr);
> init_expr = gimple_convert (stmts, type, init_expr);
> }
> break;
> --
> 2.31.1
>
