> On Aug 7, 2018, at 2:25 PM, Will Schmidt <will_schm...@vnet.ibm.com> wrote: > > Hi > Enable GIMPLE folding of the vec_splat() intrinsic. > > For review.. feedback is expected. :-) > > I came up with the following after spending some time poking around > at the tree_vec_extract() and vector_element() functions as seen > in tree-vect-generic.c looking for insights. Some of this seems a > bit clunky to me yet, but this is functional as far as make-check > can tell, and is as far as I can get without additional input. > > This uses the tree_vec_extract() function out of tree-vect-generic.c > to retrieve the splat value, which is a BIT_FIELD_REF. That function is > made non-static as part of this change. > > In review of the .gimple output, this folding takes a sample testcase > of > vector bool int testb_0 (vector bool int x) > { > return vec_splat (x, 0b00000); > } > from: > testb_0 (__vector __bool int x) > { > __vector __bool intD.1486 D.2855; > > _1 = VIEW_CONVERT_EXPR<__vector signed intD.1468>(xD.2778); > _2 = __builtin_altivec_vspltwD.1919 (_1, 0); > D.2855 = VIEW_CONVERT_EXPR<__vector __bool intD.1486>(_2); > return D.2855; > } > to: > testb_0 (__vector __bool int x) > { > __vector __bool intD.1486 D.2855; > > _1 = VIEW_CONVERT_EXPR<__vector signed intD.1468>(xD.2778); > D.2856 = BIT_FIELD_REF <_1, 32, 0>; > _2 = {D.2856, D.2856, D.2856, D.2856}; > D.2855 = VIEW_CONVERT_EXPR<__vector __bool intD.1486>(_2); > return D.2855; > } > This looks okay. > > Testcases are being posted as a separate patch. > > OK for trunk? > Thanks, > -Will > > [gcc] > > 2018-08-07 Will Schmidt <will_schm...@vnet.ibm.com> > > * config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Add support for > early gimple folding of vec_splat(). > * tree-vect-generic.c: Remove static from tree_vec_extract() definition. > * gimple-fold.h: Add an extern define for tree_vec_extract(). > > diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c > index 35c32be..acc6b49 100644 > --- a/gcc/config/rs6000/rs6000.c > +++ b/gcc/config/rs6000/rs6000.c > @@ -15764,10 +15764,56 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator > *gsi) > tree splat_tree = build_vector_from_val (TREE_TYPE (lhs), splat_value); > g = gimple_build_assign (lhs, splat_tree); > gimple_set_location (g, gimple_location (stmt)); > gsi_replace (gsi, g, true); > return true; > + } > + > + /* Flavors of vec_splat. */ > + // a = vec_splat (b, 0x3) ; // a = { b[3],b[3],b[3],...}; > + case ALTIVEC_BUILTIN_VSPLTB: > + case ALTIVEC_BUILTIN_VSPLTH: > + case ALTIVEC_BUILTIN_VSPLTW: > + case VSX_BUILTIN_XXSPLTD_V2DI: > + case VSX_BUILTIN_XXSPLTD_V2DF: > + { > + arg0 = gimple_call_arg (stmt, 0); /* input vector. */ > + arg1 = gimple_call_arg (stmt, 1); /* index into arg0. */ > + /* Only fold the vec_splat_*() if arg1 is a constant > + 5-bit unsigned literal. */ > + if (TREE_CODE (arg1) != INTEGER_CST || TREE_INT_CST_LOW (arg1) > 0x1f) > + return false; > + > + lhs = gimple_call_lhs (stmt); > + tree lhs_type = TREE_TYPE (lhs); > + > + tree splat; > + if (TREE_CODE (arg0) == VECTOR_CST) > + splat = VECTOR_CST_ELT (arg0, TREE_INT_CST_LOW (arg1));
You should force arg1 into range before this. It should be adjusted modulo VECTOR_CST_NELTS (arg0). Yes, the underlying vsplt* instructions will handle the modulo itself, but when expanding early we should make the correction early, else something is likely to explode. Do you have a test where arg1 is less than 32 but greater than the number of elements? > + else > + { > + /* Determine (in bits) the length and start location of the > + splat value for a call to the tree_vec_extract helper. */ > + int tree_size_in_bits = TREE_INT_CST_LOW (size_in_bytes (lhs_type)) > + * BITS_PER_UNIT; I expect you should use arg0's type rather than lhs_type here. They should be the same, of course; it's just clearer. > + int splat_elem_size = tree_size_in_bits / VECTOR_CST_NELTS (arg0); > + int splat_start_bit = TREE_INT_CST_LOW (arg1) * splat_elem_size; > + /* Do not attempt to early-fold if the size + specified offset into > + the vector would touch outside of the source vector. */ > + if ((splat_start_bit + splat_elem_size) > tree_size_in_bits) > + return false; This won't be necessary once you fix the modulo issue. The rest LGTM. Thanks, Bill > + tree len = build_int_cst (bitsizetype, splat_elem_size); > + tree start = build_int_cst (bitsizetype, splat_start_bit); > + splat = tree_vec_extract (gsi, TREE_TYPE (lhs_type), arg0, > + len, start); > + } > + /* And finally, build the new vector. */ > + tree splat_tree = build_vector_from_val (lhs_type, splat); > + g = gimple_build_assign (lhs, splat_tree); > + gimple_set_location (g, gimple_location (stmt)); > + gsi_replace (gsi, g, true); > + return true; > } > > /* vec_mergel (integrals). */ > case ALTIVEC_BUILTIN_VMRGLH: > case ALTIVEC_BUILTIN_VMRGLW: > diff --git a/gcc/gimple-fold.h b/gcc/gimple-fold.h > index 04e9bfa..e634180 100644 > --- a/gcc/gimple-fold.h > +++ b/gcc/gimple-fold.h > @@ -59,10 +59,11 @@ extern tree gimple_fold_indirect_ref (tree); > extern bool gimple_fold_builtin_sprintf (gimple_stmt_iterator *); > extern bool gimple_fold_builtin_snprintf (gimple_stmt_iterator *); > extern bool arith_code_with_undefined_signed_overflow (tree_code); > extern gimple_seq rewrite_to_defined_overflow (gimple *); > extern void replace_call_with_value (gimple_stmt_iterator *, tree); > +extern tree tree_vec_extract (gimple_stmt_iterator *, tree, tree, tree, > tree); > > /* gimple_build, functionally matching fold_buildN, outputs stmts > int the provided sequence, matching and simplifying them on-the-fly. > Supposed to replace force_gimple_operand (fold_buildN (...), ...). */ > extern tree gimple_build (gimple_seq *, location_t, > diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c > index 909f790..1c9701d 100644 > --- a/gcc/tree-vect-generic.c > +++ b/gcc/tree-vect-generic.c > @@ -118,11 +118,11 @@ build_word_mode_vector_type (int nunits) > > typedef tree (*elem_op_func) (gimple_stmt_iterator *, > tree, tree, tree, tree, tree, enum tree_code, > tree); > > -static inline tree > +tree > tree_vec_extract (gimple_stmt_iterator *gsi, tree type, > tree t, tree bitsize, tree bitpos) > { > if (TREE_CODE (t) == SSA_NAME) > { > >