| Message ID | 0f3b4359-f5ff-d14c-1b15-2ae647e6fd3a@linaro.org |
|---|---|
| State | New |
| Headers | show |
Hi Richard, Thanks for the review. On 19/09/16 23:40, Richard Biener wrote: > On Sun, Sep 18, 2016 at 10:21 PM, kugan > <kugan.vivekanandarajah@linaro.org> wrote: >> Hi Richard, >> >> >> On 14/09/16 21:31, Richard Biener wrote: >>> >>> On Fri, Sep 2, 2016 at 10:09 AM, Kugan Vivekanandarajah >>> <kugan.vivekanandarajah@linaro.org> wrote: >>>> >>>> Hi Richard, >>>> >>>> On 25 August 2016 at 22:24, Richard Biener <richard.guenther@gmail.com> >>>> wrote: >>>>> >>>>> On Thu, Aug 11, 2016 at 1:09 AM, kugan >>>>> <kugan.vivekanandarajah@linaro.org> wrote: >>>>>> >>>>>> Hi, >>>>>> >>>>>> >>>>>> On 10/08/16 20:28, Richard Biener wrote: >>>>>>> >>>>>>> >>>>>>> On Wed, Aug 10, 2016 at 10:57 AM, Jakub Jelinek <jakub@redhat.com> >>>>>>> wrote: >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Aug 10, 2016 at 08:51:32AM +1000, kugan wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> I see it now. The problem is we are just looking at (-1) being in >>>>>>>>> the >>>>>>>>> ops >>>>>>>>> list for passing changed to rewrite_expr_tree in the case of >>>>>>>>> multiplication >>>>>>>>> by negate. If we have combined (-1), as in the testcase, we will >>>>>>>>> not >>>>>>>>> have >>>>>>>>> the (-1) and will pass changed=false to rewrite_expr_tree. >>>>>>>>> >>>>>>>>> We should set changed based on what happens in >>>>>>>>> try_special_add_to_ops. >>>>>>>>> Attached patch does this. Bootstrap and regression testing are >>>>>>>>> ongoing. >>>>>>>>> Is >>>>>>>>> this OK for trunk if there is no regression. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I think the bug is elsewhere. In particular in >>>>>>>> undistribute_ops_list/zero_one_operation/decrement_power. >>>>>>>> All those look problematic in this regard, they change RHS of >>>>>>>> statements >>>>>>>> to something that holds a different value, while keeping the LHS. >>>>>>>> So, generally you should instead just add a new stmt next to the old >>>>>>>> one, >>>>>>>> and adjust data structures (replace the old SSA_NAME in some ->op >>>>>>>> with >>>>>>>> the new one). decrement_power might be a problem here, dunno if all >>>>>>>> the >>>>>>>> builtins are const in all cases that DSE would kill the old one, >>>>>>>> Richard, any preferences for that? reset flow sensitive info + reset >>>>>>>> debug >>>>>>>> stmt uses, or something different? Though, replacing the LHS with a >>>>>>>> new >>>>>>>> anonymous SSA_NAME might be needed too, in case it is before SSA_NAME >>>>>>>> of >>>>>>>> a >>>>>>>> user var that doesn't yet have any debug stmts. >>>>>>> >>>>>>> >>>>>>> >>>>>>> I'd say replacing the LHS is the way to go, with calling the >>>>>>> appropriate >>>>>>> helper >>>>>>> on the old stmt to generate a debug stmt for it / its uses (would need >>>>>>> to look it >>>>>>> up here). >>>>>>> >>>>>> >>>>>> Here is an attempt to fix it. The problem arises when in >>>>>> undistribute_ops_list, we linearize_expr_tree such that NEGATE_EXPR is >>>>>> added >>>>>> (-1) MULT_EXPR (OP). Real problem starts when we handle this in >>>>>> zero_one_operation. Unlike what was done earlier, we now change the >>>>>> stmt >>>>>> (with propagate_op_to_signle use or by directly) such that the value >>>>>> computed by stmt is no longer what it used to be. Because of this, what >>>>>> is >>>>>> computed in undistribute_ops_list and rewrite_expr_tree are also >>>>>> changed. >>>>>> >>>>>> undistribute_ops_list already expects this but rewrite_expr_tree will >>>>>> not if >>>>>> we dont pass the changed as an argument. >>>>>> >>>>>> The way I am fixing this now is, in linearize_expr_tree, I set >>>>>> ops_changed >>>>>> to true if we change NEGATE_EXPR to (-1) MULT_EXPR (OP). Then when we >>>>>> call >>>>>> zero_one_operation with ops_changed = true, I replace all the LHS in >>>>>> zero_one_operation with the new SSA and replace all the uses. I also >>>>>> call >>>>>> the rewrite_expr_tree with changed = false in this case. >>>>>> >>>>>> Does this make sense? Bootstrapped and regression tested for >>>>>> x86_64-linux-gnu without any new regressions. >>>>> >>>>> >>>>> I don't think this solves the issue. zero_one_operation associates the >>>>> chain starting at the first *def and it will change the intermediate >>>>> values >>>>> of _all_ of the stmts visited until the operation to be removed is >>>>> found. >>>>> Note that this is independent of whether try_special_add_to_ops did >>>>> anything. >>>>> >>>>> Even for the regular undistribution cases we get this wrong. >>>>> >>>>> So we need to back-track in zero_one_operation, replacing each LHS >>>>> and in the end the op in the opvector of the main chain. That's >>>>> basically >>>>> the same as if we'd do a regular re-assoc operation on the sub-chains. >>>>> Take their subops, simulate zero_one_operation by >>>>> appending the cancelling operation and optimizing the oplist, and then >>>>> materializing the associated ops via rewrite_expr_tree. >>>>> >>>> Here is a draft patch which records the stmt chain when in >>>> zero_one_operation and then fixes it when OP is removed. when we >>>> update *def, that will update the ops vector. Does this looks sane? >>> >>> >>> Yes. A few comments below >>> >>> + /* PR72835 - Record the stmt chain that has to be updated such that >>> + we dont use the same LHS when the values computed are different. */ >>> + auto_vec<gimple *> stmts_to_fix; >>> >>> use auto_vec<gimple *, 64> here so we get stack allocation only most >>> of the times >> >> Done. >> >>> if (stmt_is_power_of_op (stmt, op)) >>> { >>> + make_new_ssa_for_all_defs (def, op, stmts_to_fix); >>> if (decrement_power (stmt) == 1) >>> propagate_op_to_single_use (op, stmt, def); >>> >>> for the cases you end up with propagate_op_to_single_use its argument >>> stmt is handled superfluosly in the new SSA making, I suggest to pop it >>> from the stmts_to_fix vector in that case. I suggest to break; instead >>> of return in all cases and do the make_new_ssa_for_all_defs call at >>> the function end instead. >>> >> Done. >> >>> @@ -1253,14 +1305,18 @@ zero_one_operation (tree *def, enum tree_code >>> opcode, tree op) >>> if (gimple_assign_rhs1 (stmt2) == op) >>> { >>> tree cst = build_minus_one_cst (TREE_TYPE (op)); >>> + stmts_to_fix.safe_push (stmt2); >>> + make_new_ssa_for_all_defs (def, op, stmts_to_fix); >>> propagate_op_to_single_use (cst, stmt2, def); >>> return; >>> >>> this safe_push should be unnecessary for the above reason (others are >>> conditionally unnecessary). >>> >> Done. >> >> Bootstrapped and regression tested on X86_64-linux-gnu with no new >> regression. Is this OK? > > +static void > +make_new_ssa_for_all_defs (tree *def, tree op, > + auto_vec<gimple *, 64> &stmts_to_fix) > > I think you need to use vec<gimple *> &stmts_to_fix here AFAIK. > This is what I had. With that I get: error: invalid initialization of reference of type ‘auto_vec<gimple*>&’ from expression of type ‘auto_vec<gimple*, 64ul> Is this a bug? Thanks, Kugan
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c b/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c index e69de29..468e0f0 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c @@ -0,0 +1,37 @@ +/* PR tree-optimization/72835. */ +/* { dg-do run } */ +/* { dg-options "-O2" } */ +/* { dg-require-effective-target int32plus } */ + +struct struct_1 { + unsigned int m1 : 6 ; + unsigned int m2 : 24 ; + unsigned int m3 : 6 ; +}; + +unsigned short var_32 = 0x2d10; + +struct struct_1 s1; + +void init () +{ + s1.m1 = 4; + s1.m2 = 0x7ca4b8; + s1.m3 = 24; +} + +void foo () +{ + unsigned int c + = ((unsigned int) s1.m2) * (-((unsigned int) s1.m3)) + + (var_32) * (-((unsigned int) (s1.m1))); + if (c != 4098873984) + __builtin_abort (); +} + +int main () +{ + init (); + foo (); + return 0; +} diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c index 7fd7550..24e9dd6 100644 --- a/gcc/tree-ssa-reassoc.c +++ b/gcc/tree-ssa-reassoc.c @@ -1148,6 +1148,52 @@ decrement_power (gimple *stmt) } } +/* Replace SSA defined by STMT and replace all its uses with new + SSA. Also return the new SSA. */ + +static tree +make_new_ssa_for_def (gimple *stmt) +{ + gimple *use_stmt; + use_operand_p use; + imm_use_iterator iter; + tree new_lhs; + tree lhs = gimple_assign_lhs (stmt); + + new_lhs = make_ssa_name (TREE_TYPE (lhs)); + gimple_set_lhs (stmt, new_lhs); + + /* Also need to update GIMPLE_DEBUGs. */ + FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs) + { + FOR_EACH_IMM_USE_ON_STMT (use, iter) + SET_USE (use, new_lhs); + update_stmt (use_stmt); + } + return new_lhs; +} + +/* Replace all SSAs defined in STMTS_TO_FIX and replace its + uses with new SSAs. Also do this for the stmt that defines DEF + if *DEF is not OP. */ + +static void +make_new_ssa_for_all_defs (tree *def, tree op, + auto_vec<gimple *, 64> &stmts_to_fix) +{ + unsigned i; + gimple *stmt; + + if (*def != op + && TREE_CODE (*def) == SSA_NAME + && (stmt = SSA_NAME_DEF_STMT (*def)) + && gimple_code (stmt) != GIMPLE_NOP) + *def = make_new_ssa_for_def (stmt); + + FOR_EACH_VEC_ELT (stmts_to_fix, i, stmt) + make_new_ssa_for_def (stmt); +} + /* Find the single immediate use of STMT's LHS, and replace it with OP. Remove STMT. If STMT's LHS is the same as *DEF, replace *DEF with OP as well. */ @@ -1186,6 +1232,9 @@ static void zero_one_operation (tree *def, enum tree_code opcode, tree op) { gimple *stmt = SSA_NAME_DEF_STMT (*def); + /* PR72835 - Record the stmt chain that has to be updated such that + we dont use the same LHS when the values computed are different. */ + auto_vec<gimple *, 64> stmts_to_fix; do { @@ -1196,23 +1245,29 @@ zero_one_operation (tree *def, enum tree_code opcode, tree op) if (stmt_is_power_of_op (stmt, op)) { if (decrement_power (stmt) == 1) - propagate_op_to_single_use (op, stmt, def); - return; + { + if (stmts_to_fix.length () > 0) + stmts_to_fix.pop (); + propagate_op_to_single_use (op, stmt, def); + } + break; } else if (gimple_assign_rhs_code (stmt) == NEGATE_EXPR) { if (gimple_assign_rhs1 (stmt) == op) { tree cst = build_minus_one_cst (TREE_TYPE (op)); + if (stmts_to_fix.length () > 0) + stmts_to_fix.pop (); propagate_op_to_single_use (cst, stmt, def); - return; + break; } else if (integer_minus_onep (op) || real_minus_onep (op)) { gimple_assign_set_rhs_code (stmt, TREE_CODE (gimple_assign_rhs1 (stmt))); - return; + break; } } } @@ -1228,8 +1283,10 @@ zero_one_operation (tree *def, enum tree_code opcode, tree op) { if (name == op) name = gimple_assign_rhs2 (stmt); + if (stmts_to_fix.length () > 0) + stmts_to_fix.pop (); propagate_op_to_single_use (name, stmt, def); - return; + break; } /* We might have a multiply of two __builtin_pow* calls, and @@ -1245,7 +1302,9 @@ zero_one_operation (tree *def, enum tree_code opcode, tree op) { if (decrement_power (stmt2) == 1) propagate_op_to_single_use (op, stmt2, def); - return; + else + stmts_to_fix.safe_push (stmt2); + break; } else if (is_gimple_assign (stmt2) && gimple_assign_rhs_code (stmt2) == NEGATE_EXPR) @@ -1254,14 +1313,15 @@ zero_one_operation (tree *def, enum tree_code opcode, tree op) { tree cst = build_minus_one_cst (TREE_TYPE (op)); propagate_op_to_single_use (cst, stmt2, def); - return; + break; } else if (integer_minus_onep (op) || real_minus_onep (op)) { + stmts_to_fix.safe_push (stmt2); gimple_assign_set_rhs_code (stmt2, TREE_CODE (gimple_assign_rhs1 (stmt2))); - return; + break; } } } @@ -1270,8 +1330,12 @@ zero_one_operation (tree *def, enum tree_code opcode, tree op) gcc_assert (name != op && TREE_CODE (name) == SSA_NAME); stmt = SSA_NAME_DEF_STMT (name); + stmts_to_fix.safe_push (stmt); } while (1); + + if (stmts_to_fix.length () > 0) + make_new_ssa_for_all_defs (def, op, stmts_to_fix); } /* Returns true if statement S1 dominates statement S2. Like