Message ID | 1725052.qXkxHEI06s@polaris |
---|---|
State | New |
Headers | show |
On Mon, May 11, 2015 at 4:05 PM, Eric Botcazou <ebotcazou@adacore.com> wrote: >> >Would you be OK with a slight variation of your earlier idea, i.e. >> >calling fold_stmt with a specific valueizer from fold_marked_statements >> >instead of the implicit no_follow_ssa_edges in the inliner? Something >> >like: >> > >> >tree >> >follow_anonymous_single_use_edges (tree val) >> >{ >> > >> > if (TREE_CODE (val) == SSA_NAME >> > >> > && (!SSA_NAME_VAR (val) || DECL_IGNORED_P (SSA_NAME_VAR >> > (var))) >> > && has_single_use (val)) >> > >> > return val >> > >> > return NULL_TREE; >> > >> >} >> >> Yes, that works for me as well. > > But not for GCC. :-) The propagation per se works but, since the statement is > not folded in the end, no replacement is made at all... > > So we're back to square one and anonymous constant propagation seems to be the > only way out at -O0. The attached patch implements it in a less hackish way > (and enables it unconditionally when optimizing as suggested by Jan) by doing > it just before invoking fold_stmt on the marked statements so this should make > folding more effective in the process. > > Tested (compiler only) on x86_64-suse-linux, OK for the mainline? + if (replaced && gimple_assign_single_p (stmt)) + { + tree rhs = gimple_assign_rhs1 (stmt); + + if (TREE_CODE (rhs) == ADDR_EXPR) + recompute_tree_invariant_for_addr_expr (rhs); + } this needs to handle all non-PHI stmt kinds (asms and calls), see tree-cfg.c:replace_uses_by (maybe factor out a recompute_tree_invariant_for_gimple_ops). Looking at the whole thing I think it might be better to a) _not_ propagate parameter values during the stmt copies b) _not_ mark any stmts for folding c) at fold_marked_stmts time instead treat the incoming parameter mappings (which param setup "inlined" as param_1 = value1; etc...) as a seed for the worklist of a simple SSA propagator doing sth like while (!bitmap_empty (worklist)) { tree name = ssa_name (bitmap_first_bit (worklist)); gimple stmt = SSA_NAME_DEF_STMT (name); gcc_assert (gimple_assign_single_p (stmt) && is_gimple_min_invariant (gimple_assign_rhs1 (stmt))); FOR_EACH_IMM_USE_STMT (name) { FOR_EACH_IMM_USE_ON_STMT (..) SET_USE (...) fold_stmt (use_stmt); if (gimple_assing_single_p (use_stmt) && is_gimple_min_invariant (gimple_assign_rhs1 (use_stmt))) bitmap_set_bit (worklist, SSA_NAME_VERSION (gimple_assign_lhs (use_stmt))); } bitmap_clear_bit (SSA_NAME_VERSION (name)); /* remove 'stmt' if we replaced all uses - properly generating debug stmts */ } appropriately restricted for !optimize and eventually also propagating copies for !optimize. This should make sure we keep all stmts properly folded after inlining and it should more reliably propagate constants exposed by inlining (it should be cheaper than a full SSA CCP pass because we likely visit less stmts by just taking constant parameters as propagation sources). Richard. > > 2015-05-11 Eric Botcazou <ebotcazou@adacore.com> > > * tree-inline.c: Include tree-ssa-propagate.h. > (replace_constant_uses_in): New function. > (fold_marked_statements): Call it before folding the statement. > > * gimple-expr.h (is_gimple_constant): Reorder. > * tree-ssa-propagate.c (before_dom_children): Use inline accessor. > > > -- > Eric Botcazou
Index: tree-ssa-propagate.c =================================================================== --- tree-ssa-propagate.c (revision 222673) +++ tree-ssa-propagate.c (working copy) @@ -1246,9 +1246,7 @@ substitute_and_fold_dom_walker::before_d && gimple_call_noreturn_p (stmt)) stmts_to_fixup.safe_push (stmt); - if (is_gimple_assign (stmt) - && (get_gimple_rhs_class (gimple_assign_rhs_code (stmt)) - == GIMPLE_SINGLE_RHS)) + if (gimple_assign_single_p (stmt)) { tree rhs = gimple_assign_rhs1 (stmt); Index: tree-inline.c =================================================================== --- tree-inline.c (revision 222673) +++ tree-inline.c (working copy) @@ -82,6 +82,7 @@ along with GCC; see the file COPYING3. #include "expr.h" #include "tree-dfa.h" #include "tree-ssa.h" +#include "tree-ssa-propagate.h" #include "tree-pretty-print.h" #include "except.h" #include "debug.h" @@ -4801,6 +4802,54 @@ gimple_expand_calls_inline (basic_block return inlined; } +/* Replace USE references in statement STMT with constant values. Return + true if at least one reference was replaced. + + We do it at -O0 for anonymous SSA names or SSA names of anonymous decls, + this makes it possible to generate reasonable code for operators that are + implemented as functions and inlined on constants. */ + +static bool +replace_constant_uses_in (gimple stmt) +{ + bool replaced = false; + use_operand_p use; + ssa_op_iter iter; + + FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE) + { + tree tuse = USE_FROM_PTR (use); + + if (TREE_CODE (tuse) != SSA_NAME || SSA_NAME_IS_DEFAULT_DEF (tuse)) + continue; + + if (!optimize + && SSA_NAME_VAR (tuse) + && !DECL_IGNORED_P (SSA_NAME_VAR (tuse))) + continue; + + if (!gimple_assign_single_p (SSA_NAME_DEF_STMT (tuse))) + continue; + + tree rhs = gimple_assign_rhs1 (SSA_NAME_DEF_STMT (tuse)); + if (!is_gimple_constant (rhs)) + continue; + + propagate_value (use, rhs); + + replaced = true; + } + + if (replaced && gimple_assign_single_p (stmt)) + { + tree rhs = gimple_assign_rhs1 (stmt); + + if (TREE_CODE (rhs) == ADDR_EXPR) + recompute_tree_invariant_for_addr_expr (rhs); + } + + return replaced; +} /* Walk all basic blocks created after FIRST and try to fold every statement in the STATEMENTS pointer set. */ @@ -4819,7 +4868,10 @@ fold_marked_statements (int first, hash_ if (statements->contains (gsi_stmt (gsi))) { gimple old_stmt = gsi_stmt (gsi); - tree old_decl = is_gimple_call (old_stmt) ? gimple_call_fndecl (old_stmt) : 0; + tree old_decl + = is_gimple_call (old_stmt) + ? gimple_call_fndecl (old_stmt) : NULL_TREE; + bool replaced = replace_constant_uses_in (old_stmt); if (old_decl && DECL_BUILT_IN (old_decl)) { @@ -4827,7 +4879,7 @@ fold_marked_statements (int first, hash_ we need to look at all of them. */ gimple_stmt_iterator i2 = gsi; gsi_prev (&i2); - if (fold_stmt (&gsi)) + if (fold_stmt (&gsi) || replaced) { gimple new_stmt; /* If a builtin at the end of a bb folded into nothing, @@ -4871,7 +4923,7 @@ fold_marked_statements (int first, hash_ } } } - else if (fold_stmt (&gsi)) + else if (fold_stmt (&gsi) || replaced) { /* Re-read the statement from GSI as fold_stmt() may have changed it. */ Index: gimple-expr.h =================================================================== --- gimple-expr.h (revision 222673) +++ gimple-expr.h (working copy) @@ -136,9 +136,9 @@ is_gimple_constant (const_tree t) case INTEGER_CST: case REAL_CST: case FIXED_CST: - case STRING_CST: case COMPLEX_CST: case VECTOR_CST: + case STRING_CST: return true; default: