On Tue, May 30, 2023 at 7:06 AM Ajit Agarwal <aagar...@linux.ibm.com> wrote: > > Hello Richard: > > On 22/05/23 6:26 pm, Richard Biener wrote: > > On Thu, May 18, 2023 at 9:14 AM Ajit Agarwal <aagar...@linux.ibm.com> wrote: > >> > >> Hello All: > >> > >> This patch improves code sinking pass to sink statements before call to > >> reduce > >> register pressure. > >> Review comments are incorporated. > >> > >> Bootstrapped and regtested on powerpc64-linux-gnu. > >> > >> Thanks & Regards > >> Ajit > >> > >> > >> tree-ssa-sink: Improve code sinking pass. > >> > >> Code Sinking sinks the blocks after call. This increases > >> register pressure for callee-saved registers. Improves > >> code sinking before call in the use blocks or immediate > >> dominator of use blocks. > >> > >> 2023-05-18 Ajit Kumar Agarwal <aagar...@linux.ibm.com> > >> > >> gcc/ChangeLog: > >> > >> * tree-ssa-sink.cc (statement_sink_location): Modifed to > >> move statements before calls. > >> (block_call_p): New function. > >> (def_use_same_block): New function. > >> (select_best_block): Add heuristics to select the best > >> blocks in the immediate post dominator. > >> > >> gcc/testsuite/ChangeLog: > >> > >> * gcc.dg/tree-ssa/ssa-sink-20.c: New testcase. > >> * gcc.dg/tree-ssa/ssa-sink-21.c: New testcase. > >> --- > >> gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-20.c | 16 ++ > >> gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c | 20 +++ > >> gcc/tree-ssa-sink.cc | 159 ++++++++++++++++++-- > >> 3 files changed, 185 insertions(+), 10 deletions(-) > >> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-20.c > >> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c > >> > >> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-20.c > >> b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-20.c > >> new file mode 100644 > >> index 00000000000..716bc1f9257 > >> --- /dev/null > >> +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-20.c > >> @@ -0,0 +1,16 @@ > >> +/* { dg-do compile } */ > >> +/* { dg-options "-O2 -fdump-tree-sink -fdump-tree-optimized > >> -fdump-tree-sink-stats" } */ > >> + > >> +void bar(); > >> +int j; > >> +void foo(int a, int b, int c, int d, int e, int f) > >> +{ > >> + int l; > >> + l = a + b + c + d +e + f; > >> + if (a != 5) > >> + { > >> + bar(); > >> + j = l; > >> + } > >> +} > >> +/* { dg-final { scan-tree-dump-times "Sunk statements: 5" 1 "sink" } } */ > > > > this doesn't verify the place we sink to? > > > > I am not sure how to verify the place we sink to with dg-final.
I think dejagnu supports matching multi-line regexps so I suggest to scan for the sunk expr RHS to be followed by the call? > >> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c > >> b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c > >> new file mode 100644 > >> index 00000000000..ff41e2ea8ae > >> --- /dev/null > >> +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c > >> @@ -0,0 +1,20 @@ > >> +/* { dg-do compile } */ > >> +/* { dg-options "-O2 -fdump-tree-sink-stats -fdump-tree-sink-stats" } */ > >> + > >> +void bar(); > >> +int j, x; > >> +void foo(int a, int b, int c, int d, int e, int f) > >> +{ > >> + int l; > >> + l = a + b + c + d +e + f; > >> + if (a != 5) > >> + { > >> + bar(); > >> + if (b != 3) > >> + x = 3; > >> + else > >> + x = 5; > >> + j = l; > >> + } > >> +} > >> +/* { dg-final { scan-tree-dump-times "Sunk statements: 5" 1 "sink" } } */ > > > > likewise. So both tests already pass before the patch? > > > >> diff --git a/gcc/tree-ssa-sink.cc b/gcc/tree-ssa-sink.cc > >> index 87b1d40c174..76556e7795b 100644 > >> --- a/gcc/tree-ssa-sink.cc > >> +++ b/gcc/tree-ssa-sink.cc > >> @@ -171,6 +171,72 @@ nearest_common_dominator_of_uses (def_operand_p > >> def_p, bool *debug_stmts) > >> return commondom; > >> } > >> > >> +/* Return TRUE if immediate uses of the defs in > >> + USE occur in the same block as USE, FALSE otherwise. */ > >> + > >> +bool > >> +def_use_same_block (gimple *stmt) > >> +{ > >> + use_operand_p use_p; > >> + def_operand_p def_p; > >> + imm_use_iterator imm_iter; > >> + ssa_op_iter iter; > >> + > >> + FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF) > >> + { > >> + FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p)) > >> + { > >> + if (is_gimple_debug (USE_STMT (use_p))) > >> + continue; > >> + > >> + if (use_p > > > > use_p is never null > > > >> + && (gimple_bb (USE_STMT (use_p)) == gimple_bb (stmt))) > >> + return true; > > > > the function behavior is obviously odd ... > > > >> + } > >> + } > >> + return false; > >> +} > >> + > >> +/* Return TRUE if the block has only calls, FALSE otherwise. */ > >> + > >> +bool > >> +block_call_p (basic_block bb) > >> +{ > >> + int i = 0; > >> + bool is_call = false; > >> + gimple_stmt_iterator gsi = gsi_last_bb (bb); > >> + gimple *last_stmt = gsi_stmt (gsi); > >> + > >> + if (last_stmt && gimple_code (last_stmt) == GIMPLE_COND) > >> + { > >> + if (!gsi_end_p (gsi)) > >> + gsi_prev (&gsi); > >> + > >> + for (; !gsi_end_p (gsi);) > >> + { > >> + gimple *stmt = gsi_stmt (gsi); > >> + > >> + /* We have already seen a call. */ > >> + if (is_call) > >> + return false; > > > > Likewise. Do you want to check whether a block has > > a single stmt and that is a call and that is followed by > > a condition? It looks like a very convoluted way to write this. > > > >> + > >> + if (is_gimple_call (stmt)) > >> + is_call = true; > >> + else > >> + return false; > >> + > >> + if (!gsi_end_p (gsi)) > >> + gsi_prev (&gsi); > >> + > >> + ++i; > >> + } > >> + } > >> + if (is_call && i == 1) > >> + return true; > >> + > >> + return false; > >> +} > >> + > >> /* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator > >> tree, return the best basic block between them (inclusive) to place > >> statements. > >> @@ -190,7 +256,8 @@ nearest_common_dominator_of_uses (def_operand_p def_p, > >> bool *debug_stmts) > >> static basic_block > >> select_best_block (basic_block early_bb, > >> basic_block late_bb, > >> - gimple *stmt) > >> + gimple *stmt, > >> + gimple *use) > > > > please update the function comment > > > >> { > >> basic_block best_bb = late_bb; > >> basic_block temp_bb = late_bb; > >> @@ -230,14 +297,47 @@ select_best_block (basic_block early_bb, > >> if (threshold > 100) > >> threshold = 100; > >> } > >> - > >> /* If BEST_BB is at the same nesting level, then require it to have > >> significantly lower execution frequency to avoid gratuitous > >> movement. */ > >> if (bb_loop_depth (best_bb) == bb_loop_depth (early_bb) > >> /* If result of comparsion is unknown, prefer EARLY_BB. > >> Thus use !(...>=..) rather than (...<...) */ > >> && !(best_bb->count * 100 >= early_bb->count * threshold)) > >> - return best_bb; > >> + { > >> + basic_block new_best_bb = get_immediate_dominator (CDI_DOMINATORS, > >> best_bb); > >> + /* Return best_bb if def and use are in same block otherwise > >> new_best_bb. > >> + > >> + Things to consider: > >> + > >> + new_best_bb is not equal to best_bb and early_bb. > >> + > >> + stmt is not call. > >> + > >> + new_best_bb doesnt have any phis. > >> + > >> + use basic block is not equal to early_bb. > >> + > >> + use basic block post dominates to new_best_bb. > >> + > >> + new_best_bb dominates early_bb. */ > >> + if (new_best_bb && use > >> + && (new_best_bb != best_bb) > >> + && (new_best_bb != early_bb) > >> + && !is_gimple_call (stmt) > >> + && gsi_end_p (gsi_start_phis (new_best_bb)) > >> + && (gimple_bb (use) != early_bb) > >> + && !is_gimple_call (use) > >> + && dominated_by_p (CDI_POST_DOMINATORS, new_best_bb, > >> gimple_bb(use)) > >> + && dominated_by_p (CDI_DOMINATORS, new_best_bb, early_bb) > >> + && block_call_p (new_best_bb)) > >> + { > >> + if (def_use_same_block (use)) > >> + return best_bb; > > > > given the odd implementation of the predicates this matches very very > > specific cases. > > > > Consider > > > > if (..) > > { > > foo(); > > bar(); > > ... = l; > > } > > > > and C++ where foo and bar might throw. You then likely want to sink > > before foo (). > > > > What's the reason to only consider blocks with exactly 'call; cond;' ? > > > >> + > >> + return new_best_bb; > >> + } > >> + return best_bb; > >> + } > >> > >> /* No better block found, so return EARLY_BB, which happens to be the > >> statement's original block. */ > >> @@ -439,7 +539,7 @@ statement_sink_location (gimple *stmt, basic_block > >> frombb, > >> if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb)) > >> return false; > >> > >> - commondom = select_best_block (frombb, commondom, stmt); > >> + commondom = select_best_block (frombb, commondom, stmt, NULL); > >> > >> if (commondom == frombb) > >> return false; > >> @@ -456,19 +556,58 @@ statement_sink_location (gimple *stmt, basic_block > >> frombb, > >> continue; > >> break; > >> } > >> + > >> use = USE_STMT (one_use); > >> > >> if (gimple_code (use) != GIMPLE_PHI) > >> { > >> - sinkbb = select_best_block (frombb, gimple_bb (use), stmt); > >> + sinkbb = select_best_block (frombb, gimple_bb (use), stmt, use); > >> > >> if (sinkbb == frombb) > >> return false; > >> > >> - if (sinkbb == gimple_bb (use)) > >> - *togsi = gsi_for_stmt (use); > >> - else > >> - *togsi = gsi_after_labels (sinkbb); > >> + gimple *def_stmt = SSA_NAME_DEF_STMT (DEF_FROM_PTR (def_p)); > >> + > >> + if ((gimple_bb (def_stmt) == gimple_bb (use)) > >> + && (gimple_bb (use) != sinkbb)) > >> + sinkbb = gimple_bb (use); > >> + > >> + if (sinkbb == gimple_bb (use)) > >> + { > >> + gimple_stmt_iterator gsi = gsi_last_bb (sinkbb); > >> + gimple *def_stmt = SSA_NAME_DEF_STMT (DEF_FROM_PTR > >> (def_p)); > >> + gimple *last_stmt = gsi_stmt (gsi); > >> + > >> + /* Update sinking point as stmt before call if the sinking > >> block > >> + has only calls. Otherwise update sinking point as the > >> use > >> + stmt. */ > >> + if (gsi_stmt (gsi) == use > >> + && !is_gimple_call (last_stmt) > >> + && (gimple_code (last_stmt) != GIMPLE_SWITCH) > >> + && (gimple_code (last_stmt) != GIMPLE_COND) > >> + && (gimple_code (last_stmt) != GIMPLE_GOTO) > >> + && (!gimple_vdef (use) || !def_use_same_block > >> (def_stmt))) > >> + { > >> + if (!gsi_end_p (gsi)) > >> + gsi_prev (&gsi); > >> + > >> + gimple *stmt = gsi_stmt (gsi); > >> + > >> + if (!gsi_end_p (gsi)) > >> + gsi_prev (&gsi); > >> + > >> + if (gsi_end_p (gsi) && stmt && is_gimple_call (stmt) > >> + && gsi_end_p (gsi_start_phis (sinkbb)) > >> + && !is_gimple_call (def_stmt)) > >> + *togsi = gsi_for_stmt (stmt); > >> + else > >> + *togsi = gsi_for_stmt (use); > >> + } > >> + else > >> + *togsi = gsi_for_stmt(use); > >> + } > >> + else > >> + *togsi = gsi_after_labels (sinkbb); > > > > This is very convoluted. I think that in the end you want to compute > > (once) the > > position of the first call in each block. Since we're waking the CFG > > backwards > > in post-dominator order this information can be gathered during this walk. > > This would determine the location to sink to iff the use stmt is dominated > > by > > this location (you can for example use gimple_uid to mark stmts before it). > > > > The alternative is to simply always sink to the start of blocks even for the > > use stmt block in case that has a call before the use (but you still need to > > efficiently compute that). > > > > Incorporated the above comments and sent a separate patch. > > Thanks & Regards > Ajit > > > Richard. > > > >> > >> return true; > >> } > >> @@ -480,7 +619,7 @@ statement_sink_location (gimple *stmt, basic_block > >> frombb, > >> if (!sinkbb) > >> return false; > >> > >> - sinkbb = select_best_block (frombb, sinkbb, stmt); > >> + sinkbb = select_best_block (frombb, sinkbb, stmt, NULL); > >> if (!sinkbb || sinkbb == frombb) > >> return false; > >> > >> -- > >> 2.31.1 > >>