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| author | Richard Biener <rguenther@suse.de> | 2020-10-07 10:42:12 +0200 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2020-10-07 16:55:33 +0200 |
| commit | dae673abd37d400408959497e50fe1f3fbef5533 (patch) | |
| tree | 2e35816a5dae16baaaf334b5cb1013b54e24cdfb /gcc/tree-ssa-sink.c | |
| parent | 592fe221735bdaa375b1834dd49ce125d0b600d8 (diff) | |
| download | gcc-dae673abd37d400408959497e50fe1f3fbef5533.zip gcc-dae673abd37d400408959497e50fe1f3fbef5533.tar.gz gcc-dae673abd37d400408959497e50fe1f3fbef5533.tar.bz2 | |
tree-optimization/97307 - improve sinking of loads
This improves the heuristics finding a sink location for loads that does
not cross any store.
2020-10-07 Richard Biener <rguenther@suse.de>
PR tree-optimization/97307
* tree-ssa-sink.c (statement_sink_location): Change heuristic
for not skipping stores to look for virtual definitions
rather than uses.
* gcc.dg/tree-ssa/ssa-sink-17.c: New testcase.
* gcc.dg/vect/pr65947-3.c: XFAIL.
Diffstat (limited to 'gcc/tree-ssa-sink.c')
| -rw-r--r-- | gcc/tree-ssa-sink.c | 45 |
1 files changed, 24 insertions, 21 deletions
diff --git a/gcc/tree-ssa-sink.c b/gcc/tree-ssa-sink.c index 4cc5195..ba8e557 100644 --- a/gcc/tree-ssa-sink.c +++ b/gcc/tree-ssa-sink.c @@ -369,10 +369,9 @@ statement_sink_location (gimple *stmt, basic_block frombb, return false; /* If this is a load then do not sink past any stores. - ??? This is overly simple but cheap. We basically look - for an existing load with the same VUSE in the path to one - of the sink candidate blocks and we adjust commondom to the - nearest to commondom. */ + Look for virtual definitions in the path from frombb to the sink + location computed from the real uses and if found, adjust + that it a common dominator. */ if (gimple_vuse (stmt)) { /* Do not sink loads from hard registers. */ @@ -383,29 +382,33 @@ statement_sink_location (gimple *stmt, basic_block frombb, imm_use_iterator imm_iter; use_operand_p use_p; - basic_block found = NULL; FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_vuse (stmt)) { gimple *use_stmt = USE_STMT (use_p); basic_block bb = gimple_bb (use_stmt); - /* For PHI nodes the block we know sth about - is the incoming block with the use. */ + /* For PHI nodes the block we know sth about is the incoming block + with the use. */ if (gimple_code (use_stmt) == GIMPLE_PHI) - bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src; - /* Any dominator of commondom would be ok with - adjusting commondom to that block. */ - bb = nearest_common_dominator (CDI_DOMINATORS, bb, commondom); - if (!found) - found = bb; - else if (dominated_by_p (CDI_DOMINATORS, bb, found)) - found = bb; - /* If we can't improve, stop. */ - if (found == commondom) - break; + { + /* In case the PHI node post-dominates the current insert location + we can disregard it. */ + if (commondom != bb + && dominated_by_p (CDI_POST_DOMINATORS, commondom, bb)) + continue; + bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src; + } + else if (!gimple_vdef (use_stmt)) + continue; + /* If the use is not dominated by the path entry it is not on + the path. */ + if (!dominated_by_p (CDI_DOMINATORS, bb, frombb)) + continue; + /* There is no easy way to disregard defs not on the path from + frombb to commondom so just consider them all. */ + commondom = nearest_common_dominator (CDI_DOMINATORS, bb, commondom); + if (commondom == frombb) + return false; } - commondom = found; - if (commondom == frombb) - return false; } /* Our common dominator has to be dominated by frombb in order to be a |