Enhance BCE range analysis with length "alias" case.
Rationale:
Removes bounds check when trip count uses
an array length "alias" in the SSA flow.
Yields about 5% on micro benchmark.
Bug: b/70688025
Test: test-art-host test-art-target
Change-Id: I9047432622bddba4c6afd8b309dcc5b7496912ac
diff --git a/compiler/optimizing/bounds_check_elimination.cc b/compiler/optimizing/bounds_check_elimination.cc
index 9c2068e..147df1e 100644
--- a/compiler/optimizing/bounds_check_elimination.cc
+++ b/compiler/optimizing/bounds_check_elimination.cc
@@ -302,7 +302,7 @@
ValueBound GetLower() const { return lower_; }
ValueBound GetUpper() const { return upper_; }
- bool IsConstantValueRange() { return lower_.IsConstant() && upper_.IsConstant(); }
+ bool IsConstantValueRange() const { return lower_.IsConstant() && upper_.IsConstant(); }
// If it's certain that this value range fits in other_range.
virtual bool FitsIn(ValueRange* other_range) const {
@@ -789,24 +789,33 @@
ApplyRangeFromComparison(left, block, false_successor, new_range);
}
} else if (cond == kCondNE || cond == kCondEQ) {
- if (left->IsArrayLength() && lower.IsConstant() && upper.IsConstant()) {
- // Special case:
- // length == [c,d] yields [c, d] along true
- // length != [c,d] yields [c, d] along false
- if (!lower.Equals(ValueBound::Min()) || !upper.Equals(ValueBound::Max())) {
- ValueRange* new_range = new (&allocator_) ValueRange(&allocator_, lower, upper);
- ApplyRangeFromComparison(
- left, block, cond == kCondEQ ? true_successor : false_successor, new_range);
+ if (left->IsArrayLength()) {
+ if (lower.IsConstant() && upper.IsConstant()) {
+ // Special case:
+ // length == [c,d] yields [c, d] along true
+ // length != [c,d] yields [c, d] along false
+ if (!lower.Equals(ValueBound::Min()) || !upper.Equals(ValueBound::Max())) {
+ ValueRange* new_range = new (&allocator_) ValueRange(&allocator_, lower, upper);
+ ApplyRangeFromComparison(
+ left, block, cond == kCondEQ ? true_successor : false_successor, new_range);
+ }
+ // In addition:
+ // length == 0 yields [1, max] along false
+ // length != 0 yields [1, max] along true
+ if (lower.GetConstant() == 0 && upper.GetConstant() == 0) {
+ ValueRange* new_range = new (&allocator_) ValueRange(
+ &allocator_, ValueBound(nullptr, 1), ValueBound::Max());
+ ApplyRangeFromComparison(
+ left, block, cond == kCondEQ ? false_successor : true_successor, new_range);
+ }
}
- // In addition:
- // length == 0 yields [1, max] along false
- // length != 0 yields [1, max] along true
- if (lower.GetConstant() == 0 && upper.GetConstant() == 0) {
- ValueRange* new_range = new (&allocator_) ValueRange(
- &allocator_, ValueBound(nullptr, 1), ValueBound::Max());
- ApplyRangeFromComparison(
- left, block, cond == kCondEQ ? false_successor : true_successor, new_range);
- }
+ } else if (lower.IsRelatedToArrayLength() && lower.Equals(upper)) {
+ // Special aliasing case, with x not array length itself:
+ // x == [length,length] yields x == length along true
+ // x != [length,length] yields x == length along false
+ ValueRange* new_range = new (&allocator_) ValueRange(&allocator_, lower, upper);
+ ApplyRangeFromComparison(
+ left, block, cond == kCondEQ ? true_successor : false_successor, new_range);
}
}
}