On Wed, 2012-05-23 at 13:25 +0200, Richard Guenther wrote: > On Tue, 22 May 2012, William J. Schmidt wrote: > > > Here's a revision of the hoist-adjacent-loads patch. Besides hopefully > > addressing all your comments, I added a gate of at least -O2 for this > > transformation. Let me know if you prefer a different minimum opt > > level. > > > > I'm still running SPEC tests to make sure there are no regressions when > > opening this up to non-pointer arguments. The code bootstraps on > > powerpc64-unknown-linux-gnu with no regressions. Assuming the SPEC > > numbers come out as expected, is this ok? > > > > Thanks, > > Bill > > > > > > 2012-05-22 Bill Schmidt <wschm...@linux.vnet.ibm.com> > > > > * tree-ssa-phiopt.c (tree_ssa_phiopt_worker): Add argument to forward > > declaration. > > (hoist_adjacent_loads, gate_hoist_loads): New forward declarations. > > (tree_ssa_phiopt): Call gate_hoist_loads. > > (tree_ssa_cs_elim): Add parm to tree_ssa_phiopt_worker call. > > (tree_ssa_phiopt_worker): Add do_hoist_loads to formal arg list; call > > hoist_adjacent_loads. > > (local_mem_dependence): New function. > > (hoist_adjacent_loads): Likewise. > > (gate_hoist_loads): Likewise. > > * common.opt (fhoist-adjacent-loads): New switch. > > * Makefile.in (tree-ssa-phiopt.o): Added dependencies. > > * params.def (PARAM_MIN_CMOVE_STRUCT_ALIGN): New param. > > > > > > Index: gcc/tree-ssa-phiopt.c > > =================================================================== > > --- gcc/tree-ssa-phiopt.c (revision 187728) > > +++ gcc/tree-ssa-phiopt.c (working copy) > > @@ -37,9 +37,17 @@ along with GCC; see the file COPYING3. If not see > > #include "cfgloop.h" > > #include "tree-data-ref.h" > > #include "tree-pretty-print.h" > > +#include "gimple-pretty-print.h" > > +#include "insn-config.h" > > +#include "expr.h" > > +#include "optabs.h" > > > > +#ifndef HAVE_conditional_move > > +#define HAVE_conditional_move (0) > > +#endif > > + > > static unsigned int tree_ssa_phiopt (void); > > -static unsigned int tree_ssa_phiopt_worker (bool); > > +static unsigned int tree_ssa_phiopt_worker (bool, bool); > > static bool conditional_replacement (basic_block, basic_block, > > edge, edge, gimple, tree, tree); > > static int value_replacement (basic_block, basic_block, > > @@ -53,6 +61,9 @@ static bool cond_store_replacement (basic_block, b > > static bool cond_if_else_store_replacement (basic_block, basic_block, > > basic_block); > > static struct pointer_set_t * get_non_trapping (void); > > static void replace_phi_edge_with_variable (basic_block, edge, gimple, > > tree); > > +static void hoist_adjacent_loads (basic_block, basic_block, > > + basic_block, basic_block); > > +static bool gate_hoist_loads (void); > > > > /* This pass tries to replaces an if-then-else block with an > > assignment. We have four kinds of transformations. Some of these > > @@ -138,12 +149,56 @@ static void replace_phi_edge_with_variable (basic_ > > bb2: > > x = PHI <x' (bb0), ...>; > > > > - A similar transformation is done for MAX_EXPR. */ > > + A similar transformation is done for MAX_EXPR. > > > > + > > + This pass also performs a fifth transformation of a slightly different > > + flavor. > > + > > + Adjacent Load Hoisting > > + ---------------------- > > + > > + This transformation replaces > > + > > + bb0: > > + if (...) goto bb2; else goto bb1; > > + bb1: > > + x1 = (<expr>).field1; > > + goto bb3; > > + bb2: > > + x2 = (<expr>).field2; > > + bb3: > > + # x = PHI <x1, x2>; > > + > > + with > > + > > + bb0: > > + x1 = (<expr>).field1; > > + x2 = (<expr>).field2; > > + if (...) goto bb2; else goto bb1; > > + bb1: > > + goto bb3; > > + bb2: > > + bb3: > > + # x = PHI <x1, x2>; > > + > > + The purpose of this transformation is to enable generation of > > conditional > > + move instructions such as Intel CMOVE or PowerPC ISEL. Because one of > > + the loads is speculative, the transformation is restricted to very > > + specific cases to avoid introducing a page fault. We are looking for > > + the common idiom: > > + > > + if (...) > > + x = y->left; > > + else > > + x = y->right; > > + > > + where left and right are typically adjacent pointers in a tree > > structure. */ > > + > > static unsigned int > > tree_ssa_phiopt (void) > > { > > - return tree_ssa_phiopt_worker (false); > > + return tree_ssa_phiopt_worker (false, gate_hoist_loads ()); > > } > > > > /* This pass tries to transform conditional stores into unconditional > > @@ -190,7 +245,7 @@ tree_ssa_phiopt (void) > > static unsigned int > > tree_ssa_cs_elim (void) > > { > > - return tree_ssa_phiopt_worker (true); > > + return tree_ssa_phiopt_worker (true, false); > > } > > > > /* Return the singleton PHI in the SEQ of PHIs for edges E0 and E1. */ > > @@ -227,9 +282,11 @@ static tree condstoretemp; > > /* The core routine of conditional store replacement and normal > > phi optimizations. Both share much of the infrastructure in how > > to match applicable basic block patterns. DO_STORE_ELIM is true > > - when we want to do conditional store replacement, false otherwise. */ > > + when we want to do conditional store replacement, false otherwise. > > + DO_HOIST_LOADS is true when we want to hoist adjacent loads out > > + of diamond control flow patterns, false otherwise. */ > > static unsigned int > > -tree_ssa_phiopt_worker (bool do_store_elim) > > +tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads) > > { > > basic_block bb; > > basic_block *bb_order; > > @@ -312,6 +369,20 @@ static unsigned int > > cfgchanged = true; > > continue; > > } > > + else if (do_hoist_loads > > + && EDGE_SUCC (bb1, 0)->dest == EDGE_SUCC (bb2, 0)->dest) > > + { > > + basic_block bb3 = EDGE_SUCC (bb1, 0)->dest; > > + > > + if (single_succ_p (bb1) > > + && single_succ_p (bb2) > > + && single_pred_p (bb1) > > + && single_pred_p (bb2) > > + && EDGE_COUNT (bb->succs) == 2 > > + && EDGE_COUNT (bb3->preds) == 2) > > + hoist_adjacent_loads (bb, bb1, bb2, bb3); > > + continue; > > + } > > else > > continue; > > > > @@ -1707,6 +1778,206 @@ cond_if_else_store_replacement (basic_block then_b > > return ok; > > } > > > > +/* Return TRUE if STMT has a VUSE whose corresponding VDEF is in BB. */ > > + > > +static bool > > +local_mem_dependence (gimple stmt, basic_block bb) > > +{ > > + tree vuse = gimple_vuse (stmt); > > + gimple def; > > + > > + if (!vuse) > > + return false; > > + > > + def = SSA_NAME_DEF_STMT (vuse); > > + return (def && gimple_bb (def) == bb); > > +} > > + > > +/* Given a "diamond" control-flow pattern where BB0 tests a condition, > > + BB1 and BB2 are "then" and "else" blocks dependent on this test, > > + and BB3 rejoins control flow following BB1 and BB2, look for > > + opportunities to hoist loads as follows. If BB3 contains a PHI of > > + two loads, one each occurring in BB1 and BB2, and the loads are > > + provably of adjacent fields in the same structure, then move both > > + loads into BB0. Of course this can only be done if there are no > > + dependencies preventing such motion. > > + > > + One of the hoisted loads will always be speculative, so the > > + transformation is currently conservative: > > + > > + - The fields must be strictly adjacent. > > + - The two fields must occupy a single memory block that is > > + guaranteed to not cross a page boundary. > > + > > + The last is difficult to prove, as such memory blocks should be > > + aligned on the minimum of the stack alignment boundary and the > > + alignment guaranteed by heap allocation interfaces. Thus we rely > > + on a parameter for the alignment value. > > + > > + Provided a good value is used for the last case, the first > > + restriction could possibly be relaxed. */ > > + > > +static void > > +hoist_adjacent_loads (basic_block bb0, basic_block bb1, > > + basic_block bb2, basic_block bb3) > > +{ > > + int param_align = PARAM_VALUE (PARAM_MIN_CMOVE_STRUCT_ALIGN); > > + gimple_stmt_iterator gsi; > > + > > + /* Walk the phis in bb3 looking for an opportunity. We are looking > > + for phis of two SSA names, one each of which is defined in bb1 and > > + bb2. */ > > + for (gsi = gsi_start_phis (bb3); !gsi_end_p (gsi); gsi_next (&gsi)) > > + { > > + gimple phi_stmt = gsi_stmt (gsi); > > + gimple def1, def2, defswap; > > + tree arg1, arg2, ref1, ref2, field1, field2, fieldswap; > > + tree tree_offset1, tree_offset2, tree_size2, next; > > + int offset1, offset2, size2, block_offset; > > + unsigned align1; > > + gimple_stmt_iterator gsi2; > > + > > + if (gimple_phi_num_args (phi_stmt) != 2) > > + continue; > > + > > + arg1 = gimple_phi_arg_def (phi_stmt, 0); > > + arg2 = gimple_phi_arg_def (phi_stmt, 1); > > + > > + if (TREE_CODE (arg1) != SSA_NAME > > + || TREE_CODE (arg2) != SSA_NAME > > + || SSA_NAME_IS_DEFAULT_DEF (arg1) > > + || SSA_NAME_IS_DEFAULT_DEF (arg2)) > > + continue; > > + > > + def1 = SSA_NAME_DEF_STMT (arg1); > > + def2 = SSA_NAME_DEF_STMT (arg2); > > + > > + if ((gimple_bb (def1) != bb1 || gimple_bb (def2) != bb2) > > + && (gimple_bb (def2) != bb1 || gimple_bb (def1) != bb2)) > > + continue; > > + > > + /* Unless -fhoist-adjacent-loads was specified, check the mode > > + of the arguments to be sure a conditional move can be generated > > + for it. */ > > + if (flag_hoist_adjacent_loads != 1 > > + && !optab_handler (cmov_optab, TYPE_MODE (TREE_TYPE (arg1)))) > > + continue; > > + > > + /* Both statements must be assignments whose RHS is a COMPONENT_REF. > > */ > > + if (!gimple_assign_single_p (def1) > > + || !gimple_assign_single_p (def2)) > > + continue; > > + > > + ref1 = gimple_assign_rhs1 (def1); > > + ref2 = gimple_assign_rhs1 (def2); > > + > > + if (TREE_CODE (ref1) != COMPONENT_REF > > + || TREE_CODE (ref2) != COMPONENT_REF) > > + continue; > > + > > + /* The zeroth operand of the two component references must be > > + identical. It is not sufficient to compare get_base_address of > > + the two references, because this could allow for different > > + elements of the same array in the two trees. It is not safe to > > + assume that the existence of one array element implies the > > + existence of a different one. */ > > + if (!operand_equal_p (TREE_OPERAND (ref1, 0), TREE_OPERAND (ref2, > > 0), 0)) > > + continue; > > + > > + field1 = TREE_OPERAND (ref1, 1); > > + field2 = TREE_OPERAND (ref2, 1); > > + > > + /* Check for field adjacency, and ensure field1 comes first. */ > > + for (next = DECL_CHAIN (field1); > > + next && TREE_CODE (next) != FIELD_DECL; > > + next = DECL_CHAIN (next)) > > + ; > > + > > + if (!next || !operand_equal_p (next, field2, 0)) > > You can compare FIELD_DECLS by pointer equality, thus next != field2 here. > > > + { > > + for (next = DECL_CHAIN (field2); > > + next && TREE_CODE (next) != FIELD_DECL; > > + next = DECL_CHAIN (next)) > > + ; > > + > > + if (!next || !operand_equal_p (next, field1, 0)) > > Likewise. > > > + continue; > > + > > + fieldswap = field1; > > + field1 = field2; > > + field2 = fieldswap; > > + defswap = def1; > > + def1 = def2; > > + def2 = defswap; > > + } > > + > > + /* Check for proper alignment of the first field. */ > > + tree_offset1 = bit_position (field1); > > + tree_offset2 = bit_position (field2); > > + tree_size2 = DECL_SIZE_UNIT (field2); > > + > > + if (TREE_CODE (tree_size2) != INTEGER_CST > > host_integerp already checks for the TREE_CODE. > > > + || !host_integerp (tree_offset1, 0) > > + || !host_integerp (tree_offset2, 0) > > + || !host_integerp (tree_size2, 0)) > > + continue; > > And I think you want , 1 in all cases, positive offsets/sizes. > > > + offset1 = TREE_INT_CST_LOW (tree_offset1); > > + offset2 = TREE_INT_CST_LOW (tree_offset2); > > + size2 = TREE_INT_CST_LOW (tree_size2); > > + align1 = DECL_ALIGN (field1); > > + > > + if (offset1 % BITS_PER_UNIT != 0 || offset1 % align1 != 0) > > + continue; > > Why offset1 % align1 != 0? offset1 is relative to the containing > record start while DECL_ALIGN is relative to the ultimate containing > object. Either it's redundant to check that or overly conservative. > I think what you want to check is that align1 is properly large > so you can guarantee that both fields are inside a single cache > line, thus, (offset2 - offset1 + size2) <= align1
Hm, I think really what we want is to just look within the block size established by param_align...something like: offset1 = TREE_INT_CST_LOW (tree_offset1); offset2 = TREE_INT_CST_LOW (tree_offset2); size2 = TREE_INT_CST_LOW (tree_size2); align1 = DECL_ALIGN (field1) % (param_align * BITS_PER_UNIT); if (offset1 % BITS_PER_UNIT != 0) continue; /* The two field references must fit within a block of memory that is guaranteed to be on the same page. */ if (align1 + offset2 - offset1 + size2 > param_align * BITS_PER_UNIT) continue; I.e., use the DECL_ALIGN to find where within the block we are probably starting, then make sure the extent of the two objects doesn't run past the end of the block. Sound right? > > > + offset1 /= BITS_PER_UNIT; > > + offset2 /= BITS_PER_UNIT; > > + > > + /* The two field references must fit within a block of memory that > > + is guaranteed to be on the same page. */ > > + block_offset = offset1 % param_align; > > See above - offset1 has no interesting meaning. > > > + > > + if (block_offset + offset2 - offset1 + size2 > param_align) > > + continue; > > + /* The two expressions cannot be dependent upon vdefs defined > > + in bb1/bb2. */ > > + if (local_mem_dependence (def1, bb1) || local_mem_dependence (def2, > > bb2)) > > + continue; > > + > > + /* The conditions are satisfied; hoist the loads from bb1 and bb2 > > into > > + bb0. We hoist the first one first so that a cache miss is handled > > + efficiently regardless of hardware cache-fill policy. */ > > + gsi2 = gsi_for_stmt (def1); > > + gsi_move_to_bb_end (&gsi2, bb0); > > + gsi2 = gsi_for_stmt (def2); > > + gsi_move_to_bb_end (&gsi2, bb0); > > + > > + if (dump_file && (dump_flags & TDF_DETAILS)) > > + { > > + fprintf (dump_file, > > + "\nHoisting adjacent loads from %d and %d into %d: \n", > > + bb1->index, bb2->index, bb0->index); > > + print_gimple_stmt (dump_file, def1, 0, TDF_VOPS|TDF_MEMSYMS); > > + print_gimple_stmt (dump_file, def2, 0, TDF_VOPS|TDF_MEMSYMS); > > + } > > + } > > +} > > + > > +/* Determine whether we should attempt to hoist adjacent loads out of > > + diamond patterns in pass_phiopt. Always hoist loads if > > + -fhoist-adjacent-loads is specified, or if the target machine has > > + a conditional move instruction and -fno-hoist-adjacent-loads is > > + not specified. */ > > + > > +static bool > > +gate_hoist_loads (void) > > +{ > > + return ((optimize > 1) > > + && (flag_hoist_adjacent_loads == 1 > > + || (HAVE_conditional_move && flag_hoist_adjacent_loads != 0))); > > Rather than check optimize > 1 here properly initialize it with 1 and > put it into the default_options_table. > > Thanks, > Richard. > > > +} > > + > > /* Always do these optimizations if we have SSA > > trees to work on. */ > > static bool > > Index: gcc/common.opt > > =================================================================== > > --- gcc/common.opt (revision 187728) > > +++ gcc/common.opt (working copy) > > @@ -1186,6 +1186,11 @@ fgraphite-identity > > Common Report Var(flag_graphite_identity) Optimization > > Enable Graphite Identity transformation > > > > +fhoist-adjacent-loads > > +Common Report Var(flag_hoist_adjacent_loads) Init(-1) Optimization > > +Enable hoisting adjacent loads to encourage generating conditional move > > +instructions > > + > > floop-parallelize-all > > Common Report Var(flag_loop_parallelize_all) Optimization > > Mark all loops as parallel > > Index: gcc/Makefile.in > > =================================================================== > > --- gcc/Makefile.in (revision 187728) > > +++ gcc/Makefile.in (working copy) > > @@ -2355,7 +2355,8 @@ tree-ssa-phiopt.o : tree-ssa-phiopt.c $(CONFIG_H) > > $(TM_H) $(GGC_H) $(TREE_H) $(TM_P_H) $(BASIC_BLOCK_H) \ > > $(TREE_FLOW_H) $(TREE_PASS_H) $(TREE_DUMP_H) langhooks.h $(FLAGS_H) \ > > $(DIAGNOSTIC_H) $(TIMEVAR_H) pointer-set.h domwalk.h $(CFGLOOP_H) \ > > - $(TREE_DATA_REF_H) tree-pretty-print.h > > + $(TREE_DATA_REF_H) tree-pretty-print.h gimple-pretty-print.h \ > > + insn-config.h $(EXPR_H) $(OPTABS_H) > > tree-nrv.o : tree-nrv.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \ > > $(TM_H) $(TREE_H) $(FUNCTION_H) $(BASIC_BLOCK_H) $(FLAGS_H) \ > > $(DIAGNOSTIC_H) $(TREE_FLOW_H) $(TIMEVAR_H) $(TREE_DUMP_H) > > $(TREE_PASS_H) \ > > Index: gcc/params.def > > =================================================================== > > --- gcc/params.def (revision 187728) > > +++ gcc/params.def (working copy) > > @@ -979,6 +979,13 @@ DEFPARAM (PARAM_MAX_TRACKED_STRLENS, > > "track string lengths", > > 1000, 0, 0) > > > > +/* For adjacent load hoisting transformation in tree-ssa-phiopt.c. */ > > +DEFPARAM (PARAM_MIN_CMOVE_STRUCT_ALIGN, > > + "min-cmove-struct-align", > > + "Minimum byte alignment to assume for structures in the stack " > > + "or heap when considering load hoisting for conditional moves", > > + 16, 8, 256) > > + > > /* > > Local variables: > > mode:c > > > > > > >