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| author | Richard Biener <rguenther@suse.de> | 2020-10-30 13:32:32 +0100 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2020-10-30 13:35:24 +0100 |
| commit | 82ff7e3426ea926d090777173977f8bedd086816 (patch) | |
| tree | 35c9a956bdc58f6e0d758fd31f88133a78f41f16 | |
| parent | 33c0f246f799b7403171e97f31276a8feddd05c9 (diff) | |
| download | gcc-82ff7e3426ea926d090777173977f8bedd086816.zip gcc-82ff7e3426ea926d090777173977f8bedd086816.tar.gz gcc-82ff7e3426ea926d090777173977f8bedd086816.tar.bz2 | |
tree-optimization/97623 - avoid excessive insert iteration for hoisting
This avoids requiring insert iteration for back-to-back hoisting
opportunities as seen in the added testcase. For the PR at hand
this halves the number of insert iterations retaining only
the hard to avoid PRE / hoist insert back-to-backs.
2020-10-30 Richard Biener <rguenther@suse.de>
PR tree-optimization/97623
* tree-ssa-pre.c (insert): First do hoist insertion in
a backward walk.
* gcc.dg/tree-ssa/ssa-hoist-7.c: New testcase.
| -rw-r--r-- | gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c | 54 | ||||
| -rw-r--r-- | gcc/tree-ssa-pre.c | 13 |
2 files changed, 63 insertions, 4 deletions
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c new file mode 100644 index 0000000..ce9cec6 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c @@ -0,0 +1,54 @@ +/* { dg-options "-O2 -fdump-tree-pre-stats" } */ + +void baz(); +int tem; +void foo (int a, int b, int c, int d, int e, int x, int y, int z) +{ + if (a) + { + if (b) + { + if (c) + { + if (d) + { + if (e) + { + tem = x + y; + } + else + { + if (z) baz (); + tem = x + y; + } + } + else + { + if (z) baz (); + tem = x + y; + } + } + else + { + if (z) baz (); + tem = x + y; + } + } + else + { + if (z) baz (); + tem = x + y; + } + } + else + { + if (z) baz (); + tem = x + y; + } +} + +/* Now inserting x + y five times is unnecessary but the cascading + cannot be avoided with the simple-minded dataflow. But make sure + we do the insertions all in the first iteration. */ +/* { dg-final { scan-tree-dump "insert iterations == 2" "pre" } } */ +/* { dg-final { scan-tree-dump "HOIST inserted: 5" "pre" } } */ diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c index bcef972..091ecb3 100644 --- a/gcc/tree-ssa-pre.c +++ b/gcc/tree-ssa-pre.c @@ -3646,6 +3646,15 @@ insert (void) fprintf (dump_file, "Starting insert iteration %d\n", num_iterations); changed = false; + /* Insert expressions for hoisting. Do a backward walk here since + inserting into BLOCK exposes new opportunities in its predecessors. */ + if (flag_code_hoisting) + for (int idx = rpo_num - 1; idx >= 0; --idx) + { + basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]); + if (EDGE_COUNT (block->succs) >= 2) + changed |= do_hoist_insertion (block); + } for (int idx = 0; idx < rpo_num; ++idx) { basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]); @@ -3680,10 +3689,6 @@ insert (void) if (do_partial_partial) changed |= do_pre_partial_partial_insertion (block, dom); } - - /* Insert expressions for hoisting. */ - if (flag_code_hoisting && EDGE_COUNT (block->succs) >= 2) - changed |= do_hoist_insertion (block); } } |