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Re: combine permutations in gimple
On Sat, Aug 18, 2012 at 11:59 AM, Marc Glisse <marc.glisse@inria.fr> wrote:
> Hello,
>
> here is a new patch (passes bootstrap+regtest), which only combines
> permutations if the result is the identity. I'll file a PR about more
> general
> combinations to link to this conversation and the cost hook proposition.
>
> Ok?
Ok.
Thanks,
Richard.
>
> 2012-08-18 Marc Glisse <marc.glisse@inria.fr>
>
>
> gcc/
> * fold-const.c (fold_ternary_loc): Detect identity permutations.
> Canonicalize permutations more.
> * tree-ssa-forwprop.c (is_combined_permutation_identity): New
> function.
>
> (simplify_permutation): Likewise.
> (ssa_forward_propagate_and_combine): Call it.
>
> gcc/testsuite/
> * gcc.dg/tree-ssa/forwprop-19.c: New testcase.
> * gcc.dg/fold-perm.c: Likewise.
>
> --
> Marc Glisse
> Index: gcc/fold-const.c
> ===================================================================
> --- gcc/fold-const.c (revision 190500)
> +++ gcc/fold-const.c (working copy)
> @@ -14148,58 +14148,96 @@ fold_ternary_loc (location_t loc, enum t
> return fold_build2_loc (loc, PLUS_EXPR, type,
> const_binop (MULT_EXPR, arg0, arg1), arg2);
> if (integer_zerop (arg2))
> return fold_build2_loc (loc, MULT_EXPR, type, arg0, arg1);
>
> return fold_fma (loc, type, arg0, arg1, arg2);
>
> case VEC_PERM_EXPR:
> if (TREE_CODE (arg2) == VECTOR_CST)
> {
> - unsigned int nelts = TYPE_VECTOR_SUBPARTS (type), i;
> + unsigned int nelts = TYPE_VECTOR_SUBPARTS (type), i, mask;
> unsigned char *sel = XALLOCAVEC (unsigned char, nelts);
> tree t;
> bool need_mask_canon = false;
> + bool all_in_vec0 = true;
> + bool all_in_vec1 = true;
> + bool maybe_identity = true;
> + bool single_arg = (op0 == op1);
> + bool changed = false;
>
> + mask = single_arg ? (nelts - 1) : (2 * nelts - 1);
> gcc_assert (nelts == VECTOR_CST_NELTS (arg2));
> for (i = 0; i < nelts; i++)
> {
> tree val = VECTOR_CST_ELT (arg2, i);
> if (TREE_CODE (val) != INTEGER_CST)
> return NULL_TREE;
>
> - sel[i] = TREE_INT_CST_LOW (val) & (2 * nelts - 1);
> + sel[i] = TREE_INT_CST_LOW (val) & mask;
> if (TREE_INT_CST_HIGH (val)
> || ((unsigned HOST_WIDE_INT)
> TREE_INT_CST_LOW (val) != sel[i]))
> need_mask_canon = true;
> +
> + if (sel[i] < nelts)
> + all_in_vec1 = false;
> + else
> + all_in_vec0 = false;
> +
> + if ((sel[i] & (nelts-1)) != i)
> + maybe_identity = false;
> + }
> +
> + if (maybe_identity)
> + {
> + if (all_in_vec0)
> + return op0;
> + if (all_in_vec1)
> + return op1;
> }
>
> if ((TREE_CODE (arg0) == VECTOR_CST
> || TREE_CODE (arg0) == CONSTRUCTOR)
> && (TREE_CODE (arg1) == VECTOR_CST
> || TREE_CODE (arg1) == CONSTRUCTOR))
> {
> t = fold_vec_perm (type, arg0, arg1, sel);
> if (t != NULL_TREE)
> return t;
> }
>
> + if (all_in_vec0)
> + op1 = op0;
> + else if (all_in_vec1)
> + {
> + op0 = op1;
> + for (i = 0; i < nelts; i++)
> + sel[i] -= nelts;
> + need_mask_canon = true;
> + }
> +
> + if (op0 == op1 && !single_arg)
> + changed = true;
> +
> if (need_mask_canon && arg2 == op2)
> {
> tree *tsel = XALLOCAVEC (tree, nelts);
> tree eltype = TREE_TYPE (TREE_TYPE (arg2));
> for (i = 0; i < nelts; i++)
> tsel[i] = build_int_cst (eltype, sel[i]);
> - t = build_vector (TREE_TYPE (arg2), tsel);
> - return build3_loc (loc, VEC_PERM_EXPR, type, op0, op1, t);
> + op2 = build_vector (TREE_TYPE (arg2), tsel);
> + changed = true;
> }
> +
> + if (changed)
> + return build3_loc (loc, VEC_PERM_EXPR, type, op0, op1, op2);
> }
> return NULL_TREE;
>
> default:
> return NULL_TREE;
> } /* switch (code) */
> }
>
> /* Perform constant folding and related simplification of EXPR.
> The related simplifications include x*1 => x, x*0 => 0, etc.,
> Index: gcc/tree-ssa-forwprop.c
> ===================================================================
> --- gcc/tree-ssa-forwprop.c (revision 190500)
> +++ gcc/tree-ssa-forwprop.c (working copy)
> @@ -2570,20 +2570,109 @@ combine_conversions (gimple_stmt_iterato
> gimple_assign_set_rhs_code (stmt, CONVERT_EXPR);
> update_stmt (stmt);
> return remove_prop_source_from_use (op0) ? 2 : 1;
> }
> }
> }
>
> return 0;
> }
>
> +/* Determine whether applying the 2 permutations (mask1 then mask2)
> + gives back one of the input. */
> +
> +static int
> +is_combined_permutation_identity (tree mask1, tree mask2)
> +{
> + tree mask;
> + unsigned int nelts, i, j;
> + bool maybe_identity1 = true;
> + bool maybe_identity2 = true;
> +
> + gcc_checking_assert (TREE_CODE (mask1) == VECTOR_CST
> + && TREE_CODE (mask2) == VECTOR_CST);
> + mask = fold_ternary (VEC_PERM_EXPR, TREE_TYPE (mask1), mask1, mask1,
> mask2);
> + gcc_assert (TREE_CODE (mask) == VECTOR_CST);
> +
> + nelts = VECTOR_CST_NELTS (mask);
> + for (i = 0; i < nelts; i++)
> + {
> + tree val = VECTOR_CST_ELT (mask, i);
> + gcc_assert (TREE_CODE (val) == INTEGER_CST);
> + j = TREE_INT_CST_LOW (val) & (2 * nelts - 1);
> + if (j == i)
> + maybe_identity2 = false;
> + else if (j == i + nelts)
> + maybe_identity1 = false;
> + else
> + return 0;
> + }
> + return maybe_identity1 ? 1 : maybe_identity2 ? 2 : 0;
> +}
> +
> +/* Combine two shuffles in a row. Returns 1 if there were any changes
> + made, 2 if cfg-cleanup needs to run. Else it returns 0. */
> +
> +static int
> +simplify_permutation (gimple_stmt_iterator *gsi)
> +{
> + gimple stmt = gsi_stmt (*gsi);
> + gimple def_stmt;
> + tree op0, op1, op2, op3;
> + enum tree_code code = gimple_assign_rhs_code (stmt);
> + enum tree_code code2;
> +
> + gcc_checking_assert (code == VEC_PERM_EXPR);
> +
> + op0 = gimple_assign_rhs1 (stmt);
> + op1 = gimple_assign_rhs2 (stmt);
> + op2 = gimple_assign_rhs3 (stmt);
> +
> + if (TREE_CODE (op0) != SSA_NAME)
> + return 0;
> +
> + if (TREE_CODE (op2) != VECTOR_CST)
> + return 0;
> +
> + if (op0 != op1)
> + return 0;
> +
> + def_stmt = SSA_NAME_DEF_STMT (op0);
> + if (!def_stmt || !is_gimple_assign (def_stmt)
> + || !can_propagate_from (def_stmt))
> + return 0;
> +
> + code2 = gimple_assign_rhs_code (def_stmt);
> +
> + /* Two consecutive shuffles. */
> + if (code2 == VEC_PERM_EXPR)
> + {
> + tree orig;
> + int ident;
> + op3 = gimple_assign_rhs3 (def_stmt);
> + if (TREE_CODE (op3) != VECTOR_CST)
> + return 0;
> + ident = is_combined_permutation_identity (op3, op2);
> + if (!ident)
> + return 0;
> + orig = (ident == 1) ? gimple_assign_rhs1 (def_stmt)
> + : gimple_assign_rhs2 (def_stmt);
> + gimple_assign_set_rhs1 (stmt, unshare_expr (orig));
> + gimple_assign_set_rhs_code (stmt, TREE_CODE (orig));
> + gimple_set_num_ops (stmt, 2);
> + update_stmt (stmt);
> + return remove_prop_source_from_use (op0) ? 2 : 1;
> + }
> +
> + return false;
> +}
> +
> /* Main entry point for the forward propagation and statement combine
> optimizer. */
>
> static unsigned int
> ssa_forward_propagate_and_combine (void)
> {
> basic_block bb;
> unsigned int todoflags = 0;
>
> cfg_changed = false;
> @@ -2732,20 +2821,27 @@ ssa_forward_propagate_and_combine (void)
> changed = associate_pointerplus (&gsi);
> else if (CONVERT_EXPR_CODE_P (code)
> || code == FLOAT_EXPR
> || code == FIX_TRUNC_EXPR)
> {
> int did_something = combine_conversions (&gsi);
> if (did_something == 2)
> cfg_changed = true;
> changed = did_something != 0;
> }
> + else if (code == VEC_PERM_EXPR)
> + {
> + int did_something = simplify_permutation (&gsi);
> + if (did_something == 2)
> + cfg_changed = true;
> + changed = did_something != 0;
> + }
> break;
> }
>
> case GIMPLE_SWITCH:
> changed = simplify_gimple_switch (stmt);
> break;
>
> case GIMPLE_COND:
> {
> int did_something;
> Index: gcc/testsuite/gcc.dg/tree-ssa/forwprop-19.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/forwprop-19.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/forwprop-19.c (revision 0)
> @@ -0,0 +1,15 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-forwprop2" } */
> +
> +typedef int vec __attribute__((vector_size (4 * sizeof (int))));
> +void f (vec *x1, vec *x2)
> +{
> + vec m = { 1, 2, 3, 0 };
> + vec n = { 3, 0, 1, 2 };
> + vec y = __builtin_shuffle (*x1, *x2, n);
> + vec z = __builtin_shuffle (y, m);
> + *x1 = z;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "VEC_PERM_EXPR" "forwprop2" } } */
> +/* { dg-final { cleanup-tree-dump "forwprop2" } } */
>
> Property changes on: gcc/testsuite/gcc.dg/tree-ssa/forwprop-19.c
> ___________________________________________________________________
> Added: svn:keywords
> + Author Date Id Revision URL
> Added: svn:eol-style
> + native
>
> Index: gcc/testsuite/gcc.dg/fold-perm.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/fold-perm.c (revision 0)
> +++ gcc/testsuite/gcc.dg/fold-perm.c (revision 0)
> @@ -0,0 +1,19 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-ccp1" } */
> +
> +typedef int veci __attribute__ ((vector_size (4 * sizeof (int))));
> +
> +void fun (veci *f, veci *g, veci *h)
> +{
> + veci m = { 7, 7, 4, 6 };
> + veci n = { 0, 1, 2, 3 };
> + veci p = { 1, 1, 7, 6 };
> + *h = __builtin_shuffle (*h, *h, p);
> + *g = __builtin_shuffle (*f, *g, m);
> + *f = __builtin_shuffle (*f, *g, n);
> +}
> +
> +/* { dg-final { scan-tree-dump "VEC_PERM_EXPR.*{ 3, 3, 0, 2 }" "ccp1" } }
> */
> +/* { dg-final { scan-tree-dump "VEC_PERM_EXPR.*{ 1, 1, 3, 2 }" "ccp1" } }
> */
> +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "ccp1" } } */
> +/* { dg-final { cleanup-tree-dump "ccp1" } } */
>
> Property changes on: gcc/testsuite/gcc.dg/fold-perm.c
> ___________________________________________________________________
> Added: svn:eol-style
> + native
> Added: svn:keywords
> + Author Date Id Revision URL
>
>