2011/10/17 Richard Guenther <richard.guent...@gmail.com>: > On Mon, Oct 17, 2011 at 12:59 PM, Kai Tietz <ktiet...@googlemail.com> wrote: >> 2011/10/17 Richard Guenther <richard.guent...@gmail.com>: >>> On Fri, Oct 14, 2011 at 9:43 PM, Kai Tietz <ktiet...@googlemail.com> wrote: >>>> Hello, >>>> >>>> So I committed the gimplify patch separate. And here is the remaining >>>> fold-const patch. >>>> The important tests here are in gcc.dg/tree-ssa/builtin-expect[1-4].c, >>>> which >>>> cover the one special-case for branching. Also tree-ssa/20040204-1.c covers >>>> tests for branching code (on targets having high-engough BRANCH_COST and no >>>> special-casing - like MIPS, S/390, and AVR. >>>> >>>> ChangeLog >>>> >>>> 2011-10-14 Kai Tietz <kti...@redhat.com> >>>> >>>> * fold-const.c (simple_operand_p_2): New function. >>>> (fold_truthop): Rename to >>>> (fold_truth_andor_1): function name. >>>> Additionally remove branching creation for logical and/or. >>>> (fold_truth_andor): Handle branching creation for logical and/or >>>> here. >>>> >>>> Bootstrapped and regression-tested for all languages plus Ada and >>>> Obj-C++ on x86_64-pc-linux-gnu. >>>> Ok for apply? >>> >>> Ok with ... >>> >>>> Regards, >>>> Kai >>>> >>>> Index: gcc/gcc/fold-const.c >>>> =================================================================== >>>> --- gcc.orig/gcc/fold-const.c >>>> +++ gcc/gcc/fold-const.c >>>> @@ -112,13 +112,13 @@ static tree decode_field_reference (loca >>>> static int all_ones_mask_p (const_tree, int); >>>> static tree sign_bit_p (tree, const_tree); >>>> static int simple_operand_p (const_tree); >>>> +static bool simple_operand_p_2 (tree); >>>> static tree range_binop (enum tree_code, tree, tree, int, tree, int); >>>> static tree range_predecessor (tree); >>>> static tree range_successor (tree); >>>> static tree fold_range_test (location_t, enum tree_code, tree, tree, >>>> tree); >>>> static tree fold_cond_expr_with_comparison (location_t, tree, tree, >>>> tree, tree); >>>> static tree unextend (tree, int, int, tree); >>>> -static tree fold_truthop (location_t, enum tree_code, tree, tree, tree); >>>> static tree optimize_minmax_comparison (location_t, enum tree_code, >>>> tree, tree, tree); >>>> static tree extract_muldiv (tree, tree, enum tree_code, tree, bool *); >>>> @@ -3500,7 +3500,7 @@ optimize_bit_field_compare (location_t l >>>> return lhs; >>>> } >>>> >>>> -/* Subroutine for fold_truthop: decode a field reference. >>>> +/* Subroutine for fold_truth_andor_1: decode a field reference. >>>> >>>> If EXP is a comparison reference, we return the innermost reference. >>>> >>>> @@ -3668,7 +3668,7 @@ sign_bit_p (tree exp, const_tree val) >>>> return NULL_TREE; >>>> } >>>> >>>> -/* Subroutine for fold_truthop: determine if an operand is simple enough >>>> +/* Subroutine for fold_truth_andor_1: determine if an operand is simple >>>> enough >>>> to be evaluated unconditionally. */ >>>> >>>> static int >>>> @@ -3678,7 +3678,7 @@ simple_operand_p (const_tree exp) >>>> STRIP_NOPS (exp); >>>> >>>> return (CONSTANT_CLASS_P (exp) >>>> - || TREE_CODE (exp) == SSA_NAME >>>> + || TREE_CODE (exp) == SSA_NAME >>>> || (DECL_P (exp) >>>> && ! TREE_ADDRESSABLE (exp) >>>> && ! TREE_THIS_VOLATILE (exp) >>>> @@ -3692,6 +3692,46 @@ simple_operand_p (const_tree exp) >>>> registers aren't expensive. */ >>>> && (! TREE_STATIC (exp) || DECL_REGISTER (exp)))); >>>> } >>>> + >>>> +/* Subroutine for fold_truth_andor: determine if an operand is simple >>>> enough >>>> + to be evaluated unconditionally. >>>> + I addition to simple_operand_p, we assume that comparisons and >>>> logic-not >>>> + operations are simple, if their operands are simple, too. */ >>>> + >>>> +static bool >>>> +simple_operand_p_2 (tree exp) >>>> +{ >>>> + enum tree_code code; >>>> + >>>> + /* Strip any conversions that don't change the machine mode. */ >>>> + STRIP_NOPS (exp); >>>> + >>>> + code = TREE_CODE (exp); >>>> + >>>> + if (TREE_CODE_CLASS (code) == tcc_comparison) >>>> + return (!tree_could_trap_p (exp) >>>> + && simple_operand_p_2 (TREE_OPERAND (exp, 0)) >>>> + && simple_operand_p_2 (TREE_OPERAND (exp, 1))); >>> >>> recurse with simple_operand_p. >> >> No, as this again would reject simple operations and additionally >> wouldn't check for trapping. > > ? Your code allows arbitrarily complex expressions. Also > tree_could_trap_p obviously extents to operands.
Ah, ok. I wasn't aware that it walks into tree. >> >>>> + >>>> + if (TREE_SIDE_EFFECTS (exp) >>>> + || tree_could_trap_p (exp)) >>> >>> Move this check before the tcc_comparison check and remove the >>> then redundant tree_could_trap_p check there. >> >> Ok >> >>>> + return false; >>>> + >>>> + switch (code) >>>> + { >>>> + case SSA_NAME: >>>> + return true; >>> >>> Do not handle here, it's handled in simple_operand_p. >> >> Well, was more a short-cut here. >> >>>> + case TRUTH_NOT_EXPR: >>>> + return simple_operand_p_2 (TREE_OPERAND (exp, 0)); >>>> + case BIT_NOT_EXPR: >>>> + if (TREE_CODE (TREE_TYPE (exp)) != BOOLEAN_TYPE) >>>> + return false; >>> >>> Remove the BIT_NOT_EXPR handling. Thus, simply change this switch >>> to >> >> Why should we reject simple ~X operations from gimplified code here? > > Because this is FE triggered code. From gimple you won't ever see > such complex expressions (never even the TRUTH_AND*_EXPR variants). Hmm, I thought we might see such thing in fold and/or. But well, you might be right. >> I admit that from FE-code we won't see that, as always an integer-cast >> is done for foo (_Bool x) { ... if (~x) ... }, but from >> gimplified-code this is the general description of an boolean-typed != >> 0? >> >>> if (code == TRUTH_NOT_EXPR) >>> return simple_operand_p_2 (TREE_OPERAND (exp, 0)); >>> >>> return simple_operand_p (exp); >>> >>>> + return simple_operand_p_2 (TREE_OPERAND (exp, 0)); >>>> + default: >>>> + return simple_operand_p (exp); >>>> + } >>>> +} >>>> + >>>> >>>> /* The following functions are subroutines to fold_range_test and allow >>>> it to >>>> try to change a logical combination of comparisons into a range test. >>>> @@ -4888,7 +4928,7 @@ fold_range_test (location_t loc, enum tr >>>> return 0; >>>> } >>>> >>>> -/* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P >>>> +/* Subroutine for fold_truth_andor_1: C is an INTEGER_CST interpreted as >>>> a P >>>> bit value. Arrange things so the extra bits will be set to zero if and >>>> only if C is signed-extended to its full width. If MASK is nonzero, >>>> it is an INTEGER_CST that should be AND'ed with the extra bits. */ >>>> @@ -5025,8 +5065,8 @@ merge_truthop_with_opposite_arm (locatio >>>> We return the simplified tree or 0 if no optimization is possible. */ >>>> >>>> static tree >>>> -fold_truthop (location_t loc, enum tree_code code, tree truth_type, >>>> - tree lhs, tree rhs) >>>> +fold_truth_andor_1 (location_t loc, enum tree_code code, tree truth_type, >>>> + tree lhs, tree rhs) >>>> { >>>> /* If this is the "or" of two comparisons, we can do something if >>>> the comparisons are NE_EXPR. If this is the "and", we can do >>>> something >>>> @@ -5054,8 +5094,6 @@ fold_truthop (location_t loc, enum tree_ >>>> tree lntype, rntype, result; >>>> HOST_WIDE_INT first_bit, end_bit; >>>> int volatilep; >>>> - tree orig_lhs = lhs, orig_rhs = rhs; >>>> - enum tree_code orig_code = code; >>>> >>>> /* Start by getting the comparison codes. Fail if anything is volatile. >>>> If one operand is a BIT_AND_EXPR with the constant one, treat it as if >>>> @@ -5119,8 +5157,7 @@ fold_truthop (location_t loc, enum tree_ >>>> /* If the RHS can be evaluated unconditionally and its operands are >>>> simple, it wins to evaluate the RHS unconditionally on machines >>>> with expensive branches. In this case, this isn't a comparison >>>> - that can be merged. Avoid doing this if the RHS is a floating-point >>>> - comparison since those can trap. */ >>>> + that can be merged. */ >>>> >>>> if (BRANCH_COST (optimize_function_for_speed_p (cfun), >>>> false) >= 2 >>>> @@ -5149,13 +5186,6 @@ fold_truthop (location_t loc, enum tree_ >>>> build2 (BIT_IOR_EXPR, TREE_TYPE (ll_arg), >>>> ll_arg, rl_arg), >>>> build_int_cst (TREE_TYPE (ll_arg), 0)); >>>> - >>>> - if (LOGICAL_OP_NON_SHORT_CIRCUIT) >>>> - { >>>> - if (code != orig_code || lhs != orig_lhs || rhs != orig_rhs) >>>> - return build2_loc (loc, code, truth_type, lhs, rhs); >>>> - return NULL_TREE; >>>> - } >>>> } >>>> >>>> /* See if the comparisons can be merged. Then get all the parameters for >>>> @@ -8380,13 +8410,49 @@ fold_truth_andor (location_t loc, enum t >>>> lhs is another similar operation, try to merge its rhs with our >>>> rhs. Then try to merge our lhs and rhs. */ >>>> if (TREE_CODE (arg0) == code >>>> - && 0 != (tem = fold_truthop (loc, code, type, >>>> - TREE_OPERAND (arg0, 1), arg1))) >>>> + && 0 != (tem = fold_truth_andor_1 (loc, code, type, >>>> + TREE_OPERAND (arg0, 1), arg1))) >>>> return fold_build2_loc (loc, code, type, TREE_OPERAND (arg0, 0), tem); >>>> >>>> - if ((tem = fold_truthop (loc, code, type, arg0, arg1)) != 0) >>>> + if ((tem = fold_truth_andor_1 (loc, code, type, arg0, arg1)) != 0) >>>> return tem; >>>> >>>> + if ((code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR) >>>> + && (BRANCH_COST (optimize_function_for_speed_p (cfun), >>>> + false) >= 2) >>>> + && LOGICAL_OP_NON_SHORT_CIRCUIT >>>> + && simple_operand_p_2 (arg1)) >>>> + { >>>> + enum tree_code ncode = (code == TRUTH_ANDIF_EXPR ? TRUTH_AND_EXPR >>>> + : TRUTH_OR_EXPR); >>>> + >>>> + /* Transform ((A AND-IF B) AND-IF C) into (A AND-IF (B AND C)), >>>> + or ((A OR-IF B) OR-IF C) into (A OR-IF (B OR C)) >>>> + We don't want to pack more than two leafs to a non-IF AND/OR >>>> + expression. >>>> + If tree-code of left-hand operand isn't an AND/OR-IF code and not >>>> + equal to CODE, then we don't want to add right-hand operand. >>>> + If the inner right-hand side of left-hand operand has >>>> side-effects, >>>> + or isn't simple, then we can't add to it, as otherwise we might >>>> + destroy if-sequence. */ >>>> + if (TREE_CODE (arg0) == code >>>> + /* Needed for sequence points to handle trappings, and >>>> + side-effects. */ >>>> + && simple_operand_p_2 (TREE_OPERAND (arg0, 1))) >>>> + { >>>> + tem = fold_build2_loc (loc, ncode, type, TREE_OPERAND (arg0, 1), >>>> + arg1); >>>> + return fold_build2_loc (loc, code, type, TREE_OPERAND (arg0, 0), >>>> + tem); >>>> + } >>> >>> I see you insist on this change. Let me explain again. You do this >>> for ((A AND-IF B) AND-IF C) but you don't do this for >>> ((A AND-IF B) AND C). Why? That is what doesn't make sense ot me. >>> Thus omit this hunk. >> >> Well, first ((A AND-IF B) AND C) would be an ill sequence, as AND is >> associative. So we would simply break sequence points for && and ||. >> If left-hand operand is an AND/OR-IF then outer operand has to always >> an ?-IF operation, too. > > Why? It's something like (ptr && *ptr) & x. Whether you evaluate > x or (ptr && *ptr) first does not matter. But you have to check > whether ptr is non-null before dereferencing it. So it's clearly not > ill-formed. You may argue the transform is pointless and we should > associate the & instead. Do you? well, if you are explict writing such thing as binary-and, it would be associative anyway and code doesn't change here anything. Binary and != logical and. The point about if we see something as (A TRUTH-IF B) TRUTH B), we don't want to change it at all. The outer if for this already checks that this operation is just to be used on TRUTH-IF. To modify a TRUTH to a TRUTH is pretty point-less, isn't it? If we would allow to sink the case (A TRUTH-IF B) TRUTH C to (A TRUTH-IF (B TRUTH C)), which might be of some intererest, but still would change association rule here from point of C specification. By C standard each ||,&& is treated as a separate sequence-point. Only in case that previous and next &&/|| operand have no side-effects, we can apply to them associative law. Or do I read C-spec here wrong? Regards, Kai