On Thu, Jul 1, 2021 at 10:06 AM Jiufu Guo via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > For code like: > unsigned foo(unsigned val, unsigned start) > { > unsigned cnt = 0; > for (unsigned i = start; i > val; ++i) > cnt++; > return cnt; > } > > The number of iterations should be about UINT_MAX - start. > > There is function adjust_cond_for_loop_until_wrap which > handles similar work for const bases. > Like adjust_cond_for_loop_until_wrap, this patch enhance > function number_of_iterations_cond/number_of_iterations_lt > to analyze number of iterations for this kind of loop. > > Bootstrap and regtest pass on powerpc64le, is this ok for trunk? > > gcc/ChangeLog: > > PR tree-optimization/101145 > * tree-ssa-loop-niter.c > (number_of_iterations_until_wrap): New function. > (number_of_iterations_lt): Invoke above function. > (adjust_cond_for_loop_until_wrap): > Merge to number_of_iterations_until_wrap. > (number_of_iterations_cond): Update invokes for > adjust_cond_for_loop_until_wrap and number_of_iterations_lt. > > gcc/testsuite/ChangeLog: > > PR tree-optimization/101145 > * gcc.dg/vect/pr101145.c: New test. > * gcc.dg/vect/pr101145.inc: New test. > * gcc.dg/vect/pr101145_1.c: New test. > * gcc.dg/vect/pr101145_2.c: New test. > * gcc.dg/vect/pr101145_3.c: New test. > --- > gcc/testsuite/gcc.dg/vect/pr101145.c | 187 +++++++++++++++++++++++++ > gcc/testsuite/gcc.dg/vect/pr101145.inc | 63 +++++++++ > gcc/testsuite/gcc.dg/vect/pr101145_1.c | 15 ++ > gcc/testsuite/gcc.dg/vect/pr101145_2.c | 15 ++ > gcc/testsuite/gcc.dg/vect/pr101145_3.c | 15 ++ > gcc/tree-ssa-loop-niter.c | 150 +++++++++++--------- > 6 files changed, 380 insertions(+), 65 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/vect/pr101145.c > create mode 100644 gcc/testsuite/gcc.dg/vect/pr101145.inc > create mode 100644 gcc/testsuite/gcc.dg/vect/pr101145_1.c > create mode 100644 gcc/testsuite/gcc.dg/vect/pr101145_2.c > create mode 100644 gcc/testsuite/gcc.dg/vect/pr101145_3.c >
> diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c > index b5add827018..06db6a36ef8 100644 > --- a/gcc/tree-ssa-loop-niter.c > +++ b/gcc/tree-ssa-loop-niter.c > @@ -1473,6 +1473,86 @@ assert_loop_rolls_lt (tree type, affine_iv *iv0, > affine_iv *iv1, > } > } > > +/* Determines number of iterations of loop whose ending condition > + is IV0 < IV1 which likes: {base, -C} < n, or n < {base, C}. > + The number of iterations is stored to NITER. */ > + > +static bool > +number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0, > + affine_iv *iv1, class tree_niter_desc *niter) > +{ > + tree niter_type = unsigned_type_for (type); > + tree max, min; > + > + if (POINTER_TYPE_P (type)) > + { > + max = fold_convert (type, TYPE_MAX_VALUE (niter_type)); > + min = fold_convert (type, TYPE_MIN_VALUE (niter_type)); > + } > + else > + { > + max = TYPE_MAX_VALUE (type); > + min = TYPE_MIN_VALUE (type); > + } > + > + tree high = max, low = min, one = build_int_cst (niter_type, 1); > + tree step; > + > + /* n < {base, C}. */ > + if (integer_zerop (iv0->step) && TREE_CODE (iv1->step) == INTEGER_CST > + && !tree_int_cst_sign_bit (iv1->step)) > + { > + step = iv1->step; > + niter->niter = fold_build2 (MINUS_EXPR, niter_type, max, iv1->base); max/iv1->base could be of pointer type, not sure if this is canonical though. > + if (TREE_CODE (iv1->base) == INTEGER_CST) > + low = fold_build2 (MINUS_EXPR, type, iv1->base, one); > + else if (TREE_CODE (iv0->base) == INTEGER_CST) > + low = iv0->base; > + } > + /* {base, -C} < n. */ > + else if (TREE_CODE (iv0->step) == INTEGER_CST > + && tree_int_cst_sign_bit (iv0->step) && integer_zerop (iv1->step)) > + { > + step = fold_build1 (NEGATE_EXPR, TREE_TYPE (iv0->step), iv0->step); > + niter->niter = fold_build2 (MINUS_EXPR, niter_type, iv0->base, min); > + if (TREE_CODE (iv0->base) == INTEGER_CST) > + high = fold_build2 (PLUS_EXPR, type, iv0->base, one); > + else if (TREE_CODE (iv1->base) == INTEGER_CST) > + high = iv1->base; > + } > + else > + return false; > + > + /* (delta + step - 1) / step */ > + step = fold_convert (niter_type, step); > + niter->niter = fold_convert (niter_type, niter->niter); > + niter->niter = fold_build2 (PLUS_EXPR, niter_type, niter->niter, step); > + niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, niter->niter, > step); > + > + tree m = fold_build2 (MINUS_EXPR, niter_type, high, low); > + m = fold_convert (niter_type, m); > + mpz_t mstep, tmp, mmax; > + mpz_init (mstep); > + mpz_init (tmp); > + mpz_init (mmax); > + wi::to_mpz (wi::to_wide (step), mstep, UNSIGNED); > + wi::to_mpz (wi::to_wide (m), mmax, UNSIGNED); > + mpz_add (tmp, mmax, mstep); > + mpz_sub_ui (tmp, tmp, 1); > + mpz_fdiv_q (tmp, tmp, mstep); > + niter->max = widest_int::from (wi::from_mpz (niter_type, tmp, false), > + TYPE_SIGN (niter_type)); This computation is similar to function number_of_iterations_lt, could we factor it out into an independent function? > + mpz_clear (mstep); > + mpz_clear (tmp); > + > + niter->may_be_zero > + = fold_build2 (LE_EXPR, boolean_type_node, iv1->base, iv0->base); If iv0->base and iv1->base are constant and iv1->base <= iv0->base, the number of iteration is actually zero, but here we rely on may_be_zero (== true), which loses information. Could we specially handle this case and do a fast return? Could you test this on some more targets(x86, aarch64) please? Otherwise LGTM. Thanks, bin > + > + niter->control.no_overflow = false; > + > + return true; > +} > + > /* Determines number of iterations of loop whose ending condition > is IV0 < IV1. TYPE is the type of the iv. The number of > iterations is stored to NITER. BNDS bounds the difference > @@ -1501,6 +1581,11 @@ number_of_iterations_lt (class loop *loop, tree type, > affine_iv *iv0, > niter->bound = iv0->base; > } > > + /* {base, -C} < n, or n < {base, C} */ > + if (tree_int_cst_sign_bit (iv0->step) > + || (!integer_zerop (iv1->step) && !tree_int_cst_sign_bit (iv1->step))) > + return number_of_iterations_until_wrap (loop, type, iv0, iv1, niter); > + > delta = fold_build2 (MINUS_EXPR, niter_type, > fold_convert (niter_type, iv1->base), > fold_convert (niter_type, iv0->base)); > @@ -1665,62 +1750,6 @@ dump_affine_iv (FILE *file, affine_iv *iv) > } > } > > -/* Given exit condition IV0 CODE IV1 in TYPE, this function adjusts > - the condition for loop-until-wrap cases. For example: > - (unsigned){8, -1}_loop < 10 => {0, 1} != 9 > - 10 < (unsigned){0, max - 7}_loop => {0, 1} != 8 > - Return true if condition is successfully adjusted. */ > - > -static bool > -adjust_cond_for_loop_until_wrap (tree type, affine_iv *iv0, tree_code *code, > - affine_iv *iv1) > -{ > - /* Only support simple cases for the moment. */ > - if (TREE_CODE (iv0->base) != INTEGER_CST > - || TREE_CODE (iv1->base) != INTEGER_CST) > - return false; > - > - tree niter_type = unsigned_type_for (type), high, low; > - /* Case: i-- < 10. */ > - if (integer_zerop (iv1->step)) > - { > - /* TODO: Should handle case in which abs(step) != 1. */ > - if (!integer_minus_onep (iv0->step)) > - return false; > - /* Give up on infinite loop. */ > - if (*code == LE_EXPR > - && tree_int_cst_equal (iv1->base, TYPE_MAX_VALUE (type))) > - return false; > - high = fold_build2 (PLUS_EXPR, niter_type, > - fold_convert (niter_type, iv0->base), > - build_int_cst (niter_type, 1)); > - low = fold_convert (niter_type, TYPE_MIN_VALUE (type)); > - } > - else if (integer_zerop (iv0->step)) > - { > - /* TODO: Should handle case in which abs(step) != 1. */ > - if (!integer_onep (iv1->step)) > - return false; > - /* Give up on infinite loop. */ > - if (*code == LE_EXPR > - && tree_int_cst_equal (iv0->base, TYPE_MIN_VALUE (type))) > - return false; > - high = fold_convert (niter_type, TYPE_MAX_VALUE (type)); > - low = fold_build2 (MINUS_EXPR, niter_type, > - fold_convert (niter_type, iv1->base), > - build_int_cst (niter_type, 1)); > - } > - else > - gcc_unreachable (); > - > - iv0->base = low; > - iv0->step = fold_convert (niter_type, integer_one_node); > - iv1->base = high; > - iv1->step = build_int_cst (niter_type, 0); > - *code = NE_EXPR; > - return true; > -} > - > /* Determine the number of iterations according to condition (for staying > inside loop) which compares two induction variables using comparison > operator CODE. The induction variable on left side of the comparison > @@ -1855,15 +1884,6 @@ number_of_iterations_cond (class loop *loop, > return true; > } > > - /* Handle special case loops: while (i-- < 10) and while (10 < i++) by > - adjusting iv0, iv1 and code. */ > - if (code != NE_EXPR > - && (tree_int_cst_sign_bit (iv0->step) > - || (!integer_zerop (iv1->step) > - && !tree_int_cst_sign_bit (iv1->step))) > - && !adjust_cond_for_loop_until_wrap (type, iv0, &code, iv1)) > - return false; > - > /* OK, now we know we have a senseful loop. Handle several cases, > depending > on what comparison operator is used. */ > bound_difference (loop, iv1->base, iv0->base, &bnds); > -- > 2.17.1 >