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On 2019/7/2 4:51 PM, Richard Biener wrote:
On Tue, 2 Jul 2019, Richard Biener wrote:On Tue, 2 Jul 2019, Li Jia He wrote:On 2019/7/1 3:30 PM, Richard Biener wrote:On Fri, 28 Jun 2019, Andrew Pinski wrote:On Thu, Jun 27, 2019 at 9:55 PM Li Jia He <helijia@linux.ibm.com> wrote:On 2019/6/27 11:48 PM, Jeff Law wrote:On 6/27/19 12:11 AM, Li Jia He wrote:Hi, According to the optimizable case described by Qi Feng on issue 88784, we can combine the cases into the following: 1. x > y && x != XXX_MIN --> x > y 2. x > y && x == XXX_MIN --> false 3. x <= y && x == XXX_MIN --> x == XXX_MIN 4. x < y && x != XXX_MAX --> x < y 5. x < y && x == XXX_MAX --> false 6. x >= y && x == XXX_MAX --> x == XXX_MAX 7. x > y || x != XXX_MIN --> x != XXX_MIN 8. x <= y || x != XXX_MIN --> true 9. x <= y || x == XXX_MIN --> x <= y 10. x < y || x != XXX_MAX --> x != UXXX_MAX 11. x >= y || x != XXX_MAX --> true 12. x >= y || x == XXX_MAX --> x >= y Note: XXX_MIN represents the minimum value of type x. XXX_MAX represents the maximum value of type x. Here we don't need to care about whether the operation is signed or unsigned. For example, in the below equation: 'x > y && x != XXX_MIN --> x > y' If the x type is signed int and XXX_MIN is INT_MIN, we can optimize it to 'x > y'. However, if the type of x is unsigned int and XXX_MIN is 0, we can still optimize it to 'x > y'. The regression testing for the patch was done on GCC mainline on powerpc64le-unknown-linux-gnu (Power 9 LE) with no regressions. Is it OK for trunk ? Thanks, Lijia He gcc/ChangeLog 2019-06-27 Li Jia He <helijia@linux.ibm.com> Qi Feng <ffengqi@linux.ibm.com> PR middle-end/88784 * gimple-fold.c (and_comparisons_contain_equal_operands): New function. (and_comparisons_1): Use and_comparisons_contain_equal_operands. (or_comparisons_contain_equal_operands): New function. (or_comparisons_1): Use or_comparisons_contain_equal_operands.Would this be better done via match.pd? ISTM this transformation would be well suited for that framework.Hi, Jeff I did this because of the following test case: ` _Bool comp(unsigned x, unsigned y) { return x > y && x != 0; } ` The gimple file dumped on the power platform is: ` comp (unsigned int x, unsigned int y) { _Bool D.2837; int iftmp.0; if (x > y) goto <D.2841>; else goto <D.2839>; <D.2841>: if (x != 0) goto <D.2842>; else goto <D.2839>; <D.2842>: iftmp.0 = 1; goto <D.2840>; <D.2839>: iftmp.0 = 0; <D.2840>: D.2837 = (_Bool) iftmp.0; return D.2837; } ` However, the gimple file dumped on x86 is ` comp (unsigned int x, unsigned int y) { _Bool D.2837; _1 = x > y; _2 = x != 0; _3 = _1 & _2; _4 = (int) _3; D.2837 = (_Bool) _4; return D.2837; } ` The reason for the inconsistency between these two behaviors is param logical-op-non-short-circuit. If we add the pattern to the match.pd file, we can only optimize the situation in which the statement is in the same basic block (logical-op-non-short-circuit=1, x86). But for a cross-basic block (logical-op-non-short-circuit=0, power), match.pd can't handle this situation. Another reason is that I found out maybe_fold_and_comparisons and maybe_fold_or_comparisons are not only called by ifcombine pass but also by reassoc pass. Using this method can basically unify param logical-op-non-short-circuit=0 or 1.As mentioned before ifcombine pass should be using gimple-match instead of fold_build. Try converting ifcombine over to gimple-match infrastructure and add these to match.pd.Yes, I mentioned that in the PR. The issue is that at the moment to combine x > y with x <= y you'd have to build GENERIC trees for both or temporary GIMPLE assign with a SSA def (and then feed that into the GENERIC or GIMPLE match.pd path).Hi, I did some experimentation using ‘temporary GIMPLE with a SSA def (and then feed that into the GIMPLE match.pd path’. Could we consider the code in the attachment(I did a test and the code took effect)?No, that's excessive overhead IMHO - the whole point of these functions originally was to avoid build2 (...) on both conditionals. If we now create two SSA names and two GIMPLE statements that's too much. As said it shouldn't be rocket science to teach genmatch to auto-generate those functions from match.pd patterns but it certainly is some work (less so for somebody with genmatch knowledge). I'll give it a poke...OK, it's not so easy. I guess we could lower the cost of building SSA names / gimple stmts significantly if we allocated them on the stack like via gimple *stmt1 = XALLOCAVEC (char, gimple_size (GIMPLE_ASSIGN) + 2 * sizeof (tree)); memset (stmt1, 0, ...); gimple_set_code (stmt1, GIMPLE_ASSIGN); gimple_set_num_ops (stmt1, 3); gimple_init_singleton (stmt1); gimple_stmt_iterator gsi = gsi_for_stmt (stmt1); gimple_assign_set_rhs_with_ops (&gsi, actual operation...); tree lhs1 = XALLOCA (tree_ssa_name); memset (lhs1, 0, sizeof (tree_ssa_name)); TREE_SET_CODE (lhs1, SSA_NAME); TREE_TYPE (lhs1) = ...; gimple_assing_set_lhs (stmt1, lhs1); it's all a bit ugly and some factoring in the generic gimple machinery might easen this kind of hacks, but well... With the above you could then use gimple_match_op op (gimple_match_cond::UNCOND, BIT_AND_EXPR /* or OR */, boolean_type_node, lhs1, lhs2); if (gimple_resimplify2 (NULL, &op, follow_all_ssa_edges)) ... successfully simplified into 'op' ... with the simplification path then extracting the simplified result from 'op'. Note this deliberately leaves out passing a gimple_seq as storage for more complex simplification results to match existing behavior. Your patch has the GC allocation and SSA name (and namespace!) allocation overhead and most definitely misses releasing the SSA names you allocated. Note with the above hack the simplified result has to be checked for mentions of lhs1 or lhs2 - a case we have to reject because their definitions are transitional.
Hi, I made some changes based on the recommendations. Would you like to help me to see it again ? Sorry, it took so long time to provide the patch. Note: 1. I keep the code for and_comparisons_1 and or_comparisons_1. The reason is that I did not found a good way to handle the optimization of '((x CODE1 y) AND (x CODE2 y))' in match.pd. Maybe I missing some important information about match.pd. 2. The gimple_resimplify2 function is not used. Since stmt1, stmt2, lhs1 and lhs2 are allocated on the stack, Is there a question with the value on the stack as the return value ? I may have misunderstood Richard's intention. Thanks, Lijia He
Richard.Richard.Thanks, Lijia Hemaybe_fold_and/or_comparisons handle two exploded binary expressions while the current match.pd entries handle at most one exploded one (the outermost then, either AND or OR). But it would be definitely doable to auto-generate maybe_fold_and/or_comparisons from match.pd patterns which is what I'd ultimatively suggest to do (in some more generalized form maybe). Either with a separate genmatch invocation or as part of the --gimple processing (not sure what is more feasible here). I told Li Jia He that I don't expect him to do this work. Note I didn't review the actual patch yet. Thanks, Richard.
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0001-Auto-generate-maybe_fold_and-or_comparisons-from-mat.patch
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0002-Fix-PR88784-middle-end-is-missing-some-optimizations.patch
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