On Thu, Aug 25, 2011 at 3:15 PM, Artem Shinkarov <artyom.shinkar...@gmail.com> wrote: > On Thu, Aug 25, 2011 at 2:00 PM, Richard Guenther > <richard.guent...@gmail.com> wrote: >> On Thu, Aug 25, 2011 at 2:45 PM, Artem Shinkarov >> <artyom.shinkar...@gmail.com> wrote: >>> On Thu, Aug 25, 2011 at 12:39 PM, Richard Guenther >>> <richard.guent...@gmail.com> wrote: >>>> On Thu, Aug 25, 2011 at 1:07 PM, Artem Shinkarov >>>> <artyom.shinkar...@gmail.com> wrote: >>>>> On Thu, Aug 25, 2011 at 11:09 AM, Richard Guenther >>>>> <richard.guent...@gmail.com> wrote: >>>>>> On Thu, Aug 25, 2011 at 8:20 AM, Artem Shinkarov >>>>>> <artyom.shinkar...@gmail.com> wrote: >>>>>>> Here is a cleaned-up patch without the hook. Mostly it works in a way >>>>>>> we discussed. >>>>>>> >>>>>>> So I think it is a right time to do something about vcond patterns, >>>>>>> which would allow me to get rid of conversions that I need to put all >>>>>>> over the code. >>>>>>> >>>>>>> Also at the moment the patch breaks lto frontend with a simple example: >>>>>>> #define vector(elcount, type) \ >>>>>>> __attribute__((vector_size((elcount)*sizeof(type)))) type >>>>>>> >>>>>>> int main (int argc, char *argv[]) { >>>>>>> vector (4, float) f0; >>>>>>> vector (4, float) f1; >>>>>>> >>>>>>> f0 = f1 != f0 >>>>>>> ? (vector (4, float)){-1,-1,-1,-1} : (vector (4, >>>>>>> float)){0,0,0,0}; >>>>>>> >>>>>>> return (int)f0[argc]; >>>>>>> } >>>>>>> >>>>>>> test-lto.c:8:14: internal compiler error: in convert, at >>>>>>> lto/lto-lang.c:1244 >>>>>>> >>>>>>> I looked into the file, the conversion function is defined as >>>>>>> gcc_unreachable (). I am not very familiar with lto, so I don't really >>>>>>> know what is the right way to treat the conversions. >>>>>>> >>>>>>> And I seriously need help with backend patterns. >>>>>> >>>>>> On the patch. >>>>>> >>>>>> The documentation needs review by a native english speaker, but here >>>>>> are some factual comments: >>>>>> >>>>>> +In C vector comparison is supported within standard comparison >>>>>> operators: >>>>>> >>>>>> it should read 'In GNU C' here and everywhere else as this is a GNU >>>>>> extension. >>>>>> >>>>>> The result of the >>>>>> +comparison is a signed integer-type vector where the size of each >>>>>> +element must be the same as the size of compared vectors element. >>>>>> >>>>>> The result type of the comparison is determined by the C frontend, >>>>>> it isn't under control of the user. What you are implying here is >>>>>> restrictions on vector assignments, which are documented elsewhere. >>>>>> I'd just say >>>>>> >>>>>> 'The result of the comparison is a vector of the same width and number >>>>>> of elements as the comparison operands with a signed integral element >>>>>> type.' >>>>>> >>>>>> +In addition to the vector comparison C supports conditional expressions >>>>>> >>>>>> See above. >>>>>> >>>>>> +For the convenience condition in the vector conditional can be just a >>>>>> +vector of signed integer type. >>>>>> >>>>>> 'of integer type.' I don't see a reason to disallow unsigned integers, >>>>>> they can be equally well compared against zero. >>>>> >>>>> I'll have a final go on the documentation, it is untouched from the old >>>>> patches. >>>>> >>>>>> Index: gcc/targhooks.h >>>>>> =================================================================== >>>>>> --- gcc/targhooks.h (revision 177665) >>>>>> +++ gcc/targhooks.h (working copy) >>>>>> @@ -86,6 +86,7 @@ extern int default_builtin_vectorization >>>>>> extern tree default_builtin_reciprocal (unsigned int, bool, bool); >>>>>> >>>>>> extern bool default_builtin_vector_alignment_reachable (const_tree, >>>>>> bool); >>>>>> + >>>>>> extern bool >>>>>> default_builtin_support_vector_misalignment (enum machine_mode mode, >>>>>> const_tree, >>>>>> >>>>>> spurious whitespace change. >>>>> >>>>> Yes, thanks. >>>>> >>>>>> Index: gcc/optabs.c >>>>>> =================================================================== >>>>>> --- gcc/optabs.c (revision 177665) >>>>>> +++ gcc/optabs.c (working copy) >>>>>> @@ -6572,16 +6572,36 @@ expand_vec_cond_expr (tree vec_cond_type >>>>>> ... >>>>>> + else >>>>>> + { >>>>>> + rtx rtx_op0; >>>>>> + rtx vec; >>>>>> + >>>>>> + rtx_op0 = expand_normal (op0); >>>>>> + comparison = gen_rtx_NE (mode, NULL_RTX, NULL_RTX); >>>>>> + vec = CONST0_RTX (mode); >>>>>> + >>>>>> + create_output_operand (&ops[0], target, mode); >>>>>> + create_input_operand (&ops[1], rtx_op1, mode); >>>>>> + create_input_operand (&ops[2], rtx_op2, mode); >>>>>> + create_input_operand (&ops[3], comparison, mode); >>>>>> + create_input_operand (&ops[4], rtx_op0, mode); >>>>>> + create_input_operand (&ops[5], vec, mode); >>>>>> >>>>>> this still builds the fake(?) != comparison, but as you said you need >>>>>> help >>>>>> with the .md part if we want to use a machine specific pattern for this >>>>>> case (which we eventually want, for the sake of using XOP vcond). >>>>> >>>>> Yes, I am waiting for it. This is the only way at the moment to make >>>>> sure that in >>>>> m = a > b; >>>>> r = m ? c : d; >>>>> >>>>> m in the vcond is not transformed into the m != 0. >>>>> >>>>>> Index: gcc/target.h >>>>>> =================================================================== >>>>>> --- gcc/target.h (revision 177665) >>>>>> +++ gcc/target.h (working copy) >>>>>> @@ -51,6 +51,7 @@ >>>>>> #define GCC_TARGET_H >>>>>> >>>>>> #include "insn-modes.h" >>>>>> +#include "gimple.h" >>>>>> >>>>>> #ifdef ENABLE_CHECKING >>>>>> >>>>>> spurious change. >>>>> >>>>> Old stuff, fixed. >>>>> >>>>>> @@ -9073,26 +9082,28 @@ fold_comparison (location_t loc, enum tr >>>>>> floating-point, we can only do some of these simplifications.) */ >>>>>> if (operand_equal_p (arg0, arg1, 0)) >>>>>> { >>>>>> + tree arg0_type = TREE_TYPE (arg0); >>>>>> + >>>>>> switch (code) >>>>>> { >>>>>> case EQ_EXPR: >>>>>> - if (! FLOAT_TYPE_P (TREE_TYPE (arg0)) >>>>>> - || ! HONOR_NANS (TYPE_MODE (TREE_TYPE (arg0)))) >>>>>> + if (! FLOAT_TYPE_P (arg0_type) >>>>>> + || ! HONOR_NANS (TYPE_MODE (arg0_type))) >>>>>> ... >>>>> >>>>> Ok. >>>>> >>>>>> >>>>>> Likewise. >>>>>> >>>>>> @@ -8440,6 +8440,37 @@ expand_expr_real_2 (sepops ops, rtx targ >>>>>> case UNGE_EXPR: >>>>>> case UNEQ_EXPR: >>>>>> case LTGT_EXPR: >>>>>> + if (TREE_CODE (ops->type) == VECTOR_TYPE) >>>>>> + { >>>>>> + enum tree_code code = ops->code; >>>>>> + tree arg0 = ops->op0; >>>>>> + tree arg1 = ops->op1; >>>>>> >>>>>> move this code to do_store_flag (we really store a flag value). It >>>>>> should >>>>>> also simply do what expand_vec_cond_expr does, probably simply >>>>>> calling that with the {-1,...} {0,...} extra args should work. >>>>> >>>>> I started to do that, but the code in do_store_flag is completely >>>>> different from what I am doing, and it looks confusing. I just call >>>>> expand_vec_cond_expr and that is it. I can write a separate function, >>>>> but the code is quite small. >>>> >>>> Hm? I see in your patch >>>> >>>> Index: gcc/expr.c >>>> =================================================================== >>>> --- gcc/expr.c (revision 177665) >>>> +++ gcc/expr.c (working copy) >>>> @@ -8440,6 +8440,37 @@ expand_expr_real_2 (sepops ops, rtx targ >>>> case UNGE_EXPR: >>>> case UNEQ_EXPR: >>>> case LTGT_EXPR: >>>> + if (TREE_CODE (ops->type) == VECTOR_TYPE) >>>> + { >>>> + enum tree_code code = ops->code; >>>> + tree arg0 = ops->op0; >>>> + tree arg1 = ops->op1; >>>> + tree arg_type = TREE_TYPE (arg0); >>>> + tree el_type = TREE_TYPE (arg_type); >>>> + tree t, ifexp, if_true, if_false; >>>> + >>>> + el_type = lang_hooks.types.type_for_size (TYPE_PRECISION >>>> (el_type), 0); >>>> + >>>> + >>>> + ifexp = build2 (code, type, arg0, arg1); >>>> + if_true = build_vector_from_val (type, build_int_cst (el_type, >>>> -1)); >>>> + if_false = build_vector_from_val (type, build_int_cst (el_type, >>>> 0)); >>>> + >>>> + if (arg_type != type) >>>> + { >>>> + if_true = convert (arg_type, if_true); >>>> + if_false = convert (arg_type, if_false); >>>> + t = build3 (VEC_COND_EXPR, arg_type, ifexp, if_true, >>>> if_false); >>>> + t = convert (type, t); >>>> + } >>>> + else >>>> + t = build3 (VEC_COND_EXPR, type, ifexp, if_true, if_false); >>>> + >>>> + return expand_expr (t, >>>> + modifier != EXPAND_STACK_PARM ? target : >>>> NULL_RTX, >>>> + tmode != VOIDmode ? tmode : mode, >>>> + modifier); >>>> + } >>>> >>>> that's not exactly "calling expand_vec_cond_expr". >>> >>> Well, actually it is. Keep in mind that clean backend would imply >>> removing the conversions. But I'll make a function. >> >> Why does >> >> return expand_vec_cond_expr (build2 (ops->code, type, ops->op0, ops->op1), >> build_vector_from_val >> (type, build_int_cst (el_type, -1)), >> build_vector_from_val >> (type, build_int_cst (el_type, 0))); >> >> not work? If you push the conversions to expand_vec_cond_expr >> by doing them on RTL you simplify things here and remove the requirement >> from doing them in the C frontend for VEC_COND_EXPR as well. > > It does not work because vcond <a > b, c, d> requires a,b,c,d to have > the same type. Now here we are dealing only with comparisons, so in > case of floats we have vcond < f0 > f1, {-1,...}, {0,...}> which we > have to transform into > (vsi)(vcond< f0 >f1, (vsf){-1,...}, (vsf){0,...}>). > > Ok, so is it ok to do make this conversion here for the real types? > >>>>>> >>>>>> As for the still required conversions, you should be able to delay those >>>>>> from the C frontend (and here) to expand_vec_cond_expr by, after >>>>>> expanding op1 and op2, wrapping a subreg around it with a proper mode >>>>>> (using convert_mode (GET_MODE (comparison), rtx_op1)) should work), >>>>>> and then convert the result back to the original mode. >>>>>> >>>>>> I'll leave the C frontend pieces of the patch for review by Joseph, but >>>>> >>>>> Conversions are there until we fix the backend. When backend will be >>>>> able to digest f0 > f1 ? int0 : int1, all the conversions will go >>>>> away. >>>>> >>>>>> +static tree >>>>>> +fold_build_vec_cond_expr (tree ifexp, tree op1, tree op2) >>>>>> >>>>>> is missing a function comment. >>>>> >>>>> fixed. >>>>> >>>>>> +static tree >>>>>> +do_compare (gimple_stmt_iterator *gsi, tree inner_type, tree a, tree b, >>>>>> + tree bitpos, tree bitsize, enum tree_code code) >>>>>> +{ >>>>>> + tree cond; >>>>>> + tree comp_type; >>>>>> + >>>>>> + a = tree_vec_extract (gsi, inner_type, a, bitsize, bitpos); >>>>>> + b = tree_vec_extract (gsi, inner_type, b, bitsize, bitpos); >>>>>> + >>>>>> + comp_type = lang_hooks.types.type_for_size (TYPE_PRECISION >>>>>> (inner_type), 0); >>>>>> + >>>>>> >>>>>> Use >>>>>> >>>>>> comp_type = build_nonstandard_integer_type (TYPE_PRECISION >>>>>> (inner_type), 0); >>>>>> >>>>>> instead. But I think you don't want to use TYPE_PRECISION on >>>>>> FP types. Instead you want a signed integer type of the same (mode) >>>>>> size as the vector element type, thus >>>>>> >>>>>> comp_type = build_nonstandard_integer_type (GET_MODE_BITSIZE >>>>>> (TYPE_MODE (inner_type)), 0); >>>>> >>>>> Hm, I thought that at this stage we don't wan to know anything about >>>>> modes. I mean here I am really building the same integer type as the >>>>> operands of the comparison have. But I can use MODE_BITSIZE as well, I >>>>> don't think that it could happen that the size of the mode is >>>>> different from the size of the type. Or could it? >>>> >>>> The comparison could be on floating-point types where TYPE_PRECISION >>>> can be, for example, 80 for x87 doubles. You want an integer type >>>> of the same width, so yes, GET_MODE_BITSIZE is the correct thing >>>> to use here. >>> >>> Ok. >>> >>>>>> + cond = gimplify_build2 (gsi, code, comp_type, a, b); >>>>>> >>>>>> the result type of a comparison is boolean_type_node, not comp_type. >>>>>> >>>>>> + cond = gimplify_build2 (gsi, code, comp_type, a, b); >>>>>> + return gimplify_build3 (gsi, COND_EXPR, comp_type, cond, >>>>>> + build_int_cst (comp_type, -1), >>>>>> + build_int_cst (comp_type, 0)); >>>>>> >>>>>> writing this as >>>>>> >>>>>> + return gimplify_build3 (gsi, COND_EXPR, comp_type, >>>>>> fold_build2 (code, boolean_type_node, a, b), >>>>>> + build_int_cst (comp_type, -1), >>>>>> + build_int_cst (comp_type, 0)); >>>>>> >>>>>> will get the gimplifier a better chance at simplifcation. >>>>>> >>>>>> + if (! expand_vec_cond_expr_p (type, TYPE_MODE (type))) >>>>>> >>>>>> I think we are expecting the scalar type and the vector mode here >>>>>> from looking at the single existing caller. It probably doesn't make >>>>>> a difference (we only check TYPE_UNSIGNED of it, which should >>>>>> also work for vector types), but let's be consistent. Thus, >>>>> >>>>> Ok. >>>>> >>>>>> if (! expand_vec_cond_expr_p (TREE_TYPE (type), TYPE_MODE (type))) >>>>>> >>>>>> + if (! expand_vec_cond_expr_p (type, TYPE_MODE (type))) >>>>>> + t = expand_vector_piecewise (gsi, do_compare, type, >>>>>> + TREE_TYPE (TREE_TYPE (op0)), op0, op1, code); >>>>>> + else >>>>>> + t = gimplify_build2 (gsi, code, type, op0, op1); >>>>>> >>>>>> the else case looks odd. Why re-build a stmt that already exists? >>>>>> Simply return NULL_TREE instead? >>>>> >>>>> I can adjust. The reason it is written that way is that >>>>> expand_vector_operations_1 is using the result of the function to >>>>> update rhs. >>>> >>>> Ok, so it should check whether there was any lowering done then. >>>> >>>>>> +static tree >>>>>> +expand_vec_cond_expr_piecewise (gimple_stmt_iterator *gsi, tree exp) >>>>>> +{ >>>>>> ... >>>>>> + /* Expand vector condition inside of VEC_COND_EXPR. */ >>>>>> + if (! expand_vec_cond_expr_p (TREE_TYPE (cond), >>>>>> + TYPE_MODE (TREE_TYPE (cond)))) >>>>>> + { >>>>>> ... >>>>>> + new_rhs = expand_vector_piecewise (gsi, do_compare, >>>>>> + TREE_TYPE (cond), >>>>>> + TREE_TYPE (TREE_TYPE (op1)), >>>>>> + op0, op1, TREE_CODE (cond)); >>>>>> >>>>>> I'm not sure it is beneficial to expand a < b ? v0 : v1 to >>>>>> >>>>>> tem = { a[0] < b[0] ? -1 : 0, ... } >>>>>> v0 & tem | v1 & ~tem; >>>>>> >>>>>> instead of >>>>>> >>>>>> { a[0] < b[0] ? v0[0] : v1[0], ... } >>>>>> >>>>>> even if the bitwise operations could be carried out using vectors. >>>>>> It's definitely beneficial to do the first if the CPU can create the >>>>>> bitmask. >>>>>> >>>>> >>>>> o_O >>>>> >>>>> I thought you always wanted to do (m & v0) | (~m & v1). >>>>> Do you want to have two cases of the expansion then -- when we have >>>>> mask available and when we don't? But it is really unlikely that we >>>>> can get the mask, but cannot get vcond. Because condition is actually >>>>> vcond. So once again -- do we always expand to {a[0] > b[0] ? v[0] : >>>>> c[0], ...}? >>>> >>>> Hm, yeah. I suppose with the current setup it's hard to only >>>> get the mask but not the full vcond ;) So it probably makes >>>> sense to always expand to {a[0] > b[0] ? v[0] :c[0],...} as >>>> fallback. Sorry for the confusion ;) >>> >>> Ok. >>> >>>>>> + /* Run vecower on the expresisons we have introduced. */ >>>>>> + for (; gsi_tmp.ptr != gsi->ptr; gsi_next (&gsi_tmp)) >>>>>> + expand_vector_operations_1 (&gsi_tmp); >>>>>> >>>>>> do not use gsi.ptr directly, use gsi_stmt (gsi_tm) != gsi_stmt (gsi) >>>>>> >>>>>> +static bool >>>>>> +is_vector_comparison (gimple_stmt_iterator *gsi, tree expr) >>>>>> +{ >>>>>> >>>>>> This function is lacking a comment. >>>>>> >>>>>> @@ -450,11 +637,41 @@ expand_vector_operations_1 (gimple_stmt_ >>>>>> ... >>>>>> + /* Try to get rid from the useless vector comparison >>>>>> + x != {0,0,...} which is inserted by the typechecker. */ >>>>>> + if (COMPARISON_CLASS_P (cond) && TREE_CODE (cond) == NE_EXPR) >>>>>> >>>>>> how and why? You simply drop that comparison - that doesn't look >>>>>> correct. And in fact TREE_OPERAND (cond, 0) will never be a >>>>>> comparison - that wouldn't be valid gimple. Please leave this >>>>>> optimization to SSA based forward propagation (I can help you here >>>>>> once the patch is in). >>>>> >>>>> No-no-no. This is the second part of avoiding >>>>> m = a > b; >>>>> r = m ? v0 : v1; >>>>> >>>>> to prevent m expansion to m != {0}. >>>>> >>>>> I do not _simply_ drop the comparison. I drop it only if >>>>> is_vector_comparison returned true. It means that we can never get >>>>> into the situation that we are dropping actually a comparison inserted >>>>> by the user. But what I really want to achieve here is to drop the >>>>> comparison that the frontend inserts every time when it sees an >>>>> expression there. >>>>> >>>>> As I said earlier, tree forward propagation kicks only using -On, and >>>>> I would really like to make sure that I can get rid of useless != {0} >>>>> at any level. >>> >>>> Please don't. If the language extension forces a != 0 then it should >>>> appear at -O0. The code is fishy anyway in the way it walks stmts >>>> in is_vector_comparison. At least I don't like to see this optimization >>>> done here for the sake of -O0 in this initial patch - you could try >>>> arguing about it as a followup improvement (well, probably with not >>>> much luck). -O0 is about compile-speed and debugging, doing >>>> data-flow by walking stmts backward is slow. >>> >>> Ok, then I seriously don't see any motivation to support the >>> VEC_COND_EXPR. The following code: >>> >>> m = a > b; >>> r = (m & v0) | (~m & v1) >>> >>> gives me much more flexibility and control. What the VEC_COND_EXPR is >>> good for? Syntactical sugar? >>> >>> How about throwing away all the VEC_COND_EXPR parts supporting only >>> conditions (implicitly expressed using vconds)? If we would agree on >>> implicit conversions for real types, then this is a functionality that >>> perfectly satisfies my needs. >>> >>> I don't see any interest from the backend people and I cannot wait >>> forever, so why don't we start with a simple thing? >> >> But the simple thing is already what the backend supports. >> >> Richard. >> > > Well, it is not "what" it is "how" -- that is what we are discussing > for three weeks already. > > Ok, so the question now is, whether it is fine to have conversions > inside expand_expr_real_2? If we agree that it is ok to do, then I can > adjust the patch.
Yes, it is ok to have them there, but preferably on RTL and preferably in expand_vec_cond_expr by using simplify_gen_subreg, untested patch: Index: optabs.c =================================================================== --- optabs.c (revision 178060) +++ optabs.c (working copy) @@ -6664,16 +6664,20 @@ expand_vec_cond_expr (tree vec_cond_type comparison = vector_compare_rtx (op0, unsignedp, icode); rtx_op1 = expand_normal (op1); + rtx_op1 = simplify_gen_subreg (GET_MODE (comparison), rtx_op1, + GET_MODE (rtx_op1), 0); rtx_op2 = expand_normal (op2); + rtx_op2 = simplify_gen_subreg (GET_MODE (comparison), rtx_op2, + GET_MODE (rtx_op2), 0); - create_output_operand (&ops[0], target, mode); - create_input_operand (&ops[1], rtx_op1, mode); - create_input_operand (&ops[2], rtx_op2, mode); + create_output_operand (&ops[0], target, GET_MODE (comparison)); + create_input_operand (&ops[1], rtx_op1, GET_MODE (comparison)); + create_input_operand (&ops[2], rtx_op2, GET_MODE (comparison)); create_fixed_operand (&ops[3], comparison); create_fixed_operand (&ops[4], XEXP (comparison, 0)); create_fixed_operand (&ops[5], XEXP (comparison, 1)); expand_insn (icode, 6, ops); - return ops[0].value; + return simplify_gen_subreg (mode, ops[0].value, GET_MODE (comparison), 0); } > > Artem. >