Add empty loop exit block in transform_to_exit_first_loop_alt 2015-06-24 Tom de Vries PR tree-optimization/66642 * tree-parloops.c (transform_to_exit_first_loop_alt): Update function header comment. Rename split_edge variable to edge_at_split. Split exit edge to create new loop exit bb. Insert loop exit phis in new loop exit bb. * testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c (main): Test low iteration count case. * testsuite/libgomp.c/parloops-exit-first-loop-alt.c (init): New function, factor out of ... (main): ... here. Test low iteration count case. --- gcc/tree-parloops.c | 45 ++++++++++++++++------ .../libgomp.c/parloops-exit-first-loop-alt-3.c | 5 +++ .../libgomp.c/parloops-exit-first-loop-alt.c | 28 +++++++++++++- 3 files changed, 64 insertions(+), 14 deletions(-) diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c index df7c351..6c8aaab 100644 --- a/gcc/tree-parloops.c +++ b/gcc/tree-parloops.c @@ -1522,7 +1522,7 @@ replace_uses_in_bb_by (tree name, tree val, basic_block bb) goto : - sum_z = PHI + sum_z = PHI [1] Where is single_pred (bb latch); In the simplest case, that's . @@ -1549,14 +1549,17 @@ replace_uses_in_bb_by (tree name, tree val, basic_block bb) if (ivtmp_c < n + 1) goto ; else - goto ; + goto ; : ivtmp_b = ivtmp_a + 1; goto + : + sum_y = PHI + : - sum_z = PHI + sum_z = PHI In unified diff format: @@ -1593,9 +1596,12 @@ replace_uses_in_bb_by (tree name, tree val, basic_block bb) - goto + goto ++ : ++ sum_y = PHI + : -- sum_z = PHI -+ sum_z = PHI +- sum_z = PHI ++ sum_z = PHI Note: the example does not show any virtual phis, but these are handled more or less as reductions. @@ -1626,7 +1632,7 @@ transform_to_exit_first_loop_alt (struct loop *loop, /* Create the new_header block. */ basic_block new_header = split_block_before_cond_jump (exit->src); - edge split_edge = single_pred_edge (new_header); + edge edge_at_split = single_pred_edge (new_header); /* Redirect entry edge to new_header. */ edge entry = loop_preheader_edge (loop); @@ -1643,9 +1649,9 @@ transform_to_exit_first_loop_alt (struct loop *loop, e = redirect_edge_and_branch (post_cond_edge, header); gcc_assert (e == post_cond_edge); - /* Redirect split_edge to latch. */ - e = redirect_edge_and_branch (split_edge, latch); - gcc_assert (e == split_edge); + /* Redirect edge_at_split to latch. */ + e = redirect_edge_and_branch (edge_at_split, latch); + gcc_assert (e == edge_at_split); /* Set the new loop bound. */ gimple_cond_set_rhs (cond_stmt, bound); @@ -1697,21 +1703,36 @@ transform_to_exit_first_loop_alt (struct loop *loop, /* Set the latch arguments of the new phis to ivtmp/sum_b. */ flush_pending_stmts (post_inc_edge); - /* Register the reduction exit phis. */ + /* Create a new empty exit block, inbetween the new loop header and the old + exit block. The function separate_decls_in_region needs this block to + insert code that is active on loop exit, but not any other path. */ + basic_block new_exit_block = split_edge (exit); + + /* Insert and register the reduction exit phis. */ for (gphi_iterator gsi = gsi_start_phis (exit_block); !gsi_end_p (gsi); gsi_next (&gsi)) { gphi *phi = gsi.phi (); tree res_z = PHI_RESULT (phi); + + /* Now that we have a new exit block, duplicate the phi of the old exit + block in the new exit block to preserve loop-closed ssa. */ + edge succ_new_exit_block = single_succ_edge (new_exit_block); + edge pred_new_exit_block = single_pred_edge (new_exit_block); + tree res_y = copy_ssa_name (res_z, phi); + gphi *nphi = create_phi_node (res_y, new_exit_block); + tree res_c = PHI_ARG_DEF_FROM_EDGE (phi, succ_new_exit_block); + add_phi_arg (nphi, res_c, pred_new_exit_block, UNKNOWN_LOCATION); + add_phi_arg (phi, res_y, succ_new_exit_block, UNKNOWN_LOCATION); + if (virtual_operand_p (res_z)) continue; - tree res_c = PHI_ARG_DEF_FROM_EDGE (phi, exit); gimple reduc_phi = SSA_NAME_DEF_STMT (res_c); struct reduction_info *red = reduction_phi (reduction_list, reduc_phi); if (red != NULL) - red->keep_res = phi; + red->keep_res = nphi; } /* We're going to cancel the loop at the end of gen_parallel_loop, but until diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c index cb5bf9c..bf06e0e 100644 --- a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c +++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c @@ -36,5 +36,10 @@ main (void) if (res != 11995) abort (); + /* Test low iteration count case. */ + res = f (10); + if (res != 25) + abort (); + return 0; } diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c index 1c32ea3..35c47d7 100644 --- a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c +++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c @@ -21,8 +21,8 @@ f (unsigned int n) c[i] = a[i] + b[i]; } -int -main (void) +static void __attribute__((noclone,noinline)) +init (void) { int i, j; @@ -35,6 +35,14 @@ main (void) b[k] = (k * 3) % 7; c[k] = k * 2; } +} + +int +main (void) +{ + int i; + + init (); f (N); @@ -46,5 +54,21 @@ main (void) abort (); } + /* Test low iteration count case. */ + + init (); + + f (10); + + for (i = 0; i < N; i++) + { + unsigned int actual = c[i]; + unsigned int expected = (i < 10 + ? i + ((i * 3) % 7) + : i * 2); + if (actual != expected) + abort (); + } + return 0; } -- 1.9.1