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Add ConstantRangeList::subtract(ConstantRange) #97093

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Merged
merged 3 commits into from
Jun 28, 2024
Merged

Add ConstantRangeList::subtract(ConstantRange) #97093

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26f5104
Add ConstantRangeList::subtract(ConstantRange)
haopliu Jun 28, 2024
386d94b
Update code, comments and test
haopliu Jun 28, 2024
9b9cd84
Add an assert for the else case
haopliu Jun 28, 2024
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2 changes: 2 additions & 0 deletions llvm/include/llvm/IR/ConstantRangeList.h
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Expand Up @@ -72,6 +72,8 @@ class [[nodiscard]] ConstantRangeList {
APInt(64, Upper, /*isSigned=*/true)));
}

void subtract(const ConstantRange &SubRange);

/// Return the range list that results from the union of this
/// ConstantRangeList with another ConstantRangeList, "CRL".
ConstantRangeList unionWith(const ConstantRangeList &CRL) const;
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59 changes: 59 additions & 0 deletions llvm/lib/IR/ConstantRangeList.cpp
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Expand Up @@ -81,6 +81,65 @@ void ConstantRangeList::insert(const ConstantRange &NewRange) {
}
}

void ConstantRangeList::subtract(const ConstantRange &SubRange) {
if (SubRange.isEmptySet() || empty())
return;
assert(!SubRange.isFullSet() && "Do not support full set");
assert(SubRange.getLower().slt(SubRange.getUpper()));
assert(getBitWidth() == SubRange.getBitWidth());
// Handle common cases.
if (Ranges.back().getUpper().sle(SubRange.getLower()))
return;
if (SubRange.getUpper().sle(Ranges.front().getLower()))
return;

SmallVector<ConstantRange, 2> Result;
auto AppendRangeIfNonEmpty = [&Result](APInt Start, APInt End) {
if (Start.slt(End))
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might be helpful to have brief comment "append new range if not empty" (was initially less clear why the slt check)

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I'd rename this to AppendRangeIfNonEmpty or something like that

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Renamed!

Result.push_back(ConstantRange(Start, End));
};
for (auto &Range : Ranges) {
if (SubRange.getUpper().sle(Range.getLower()) ||
Range.getUpper().sle(SubRange.getLower())) {
// "Range" and "SubRange" do not overlap.
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nice explanations =)

// L---U : Range
// L---U : SubRange (Case1)
// L---U : SubRange (Case2)
Result.push_back(Range);
} else if (Range.getLower().sle(SubRange.getLower()) &&
SubRange.getUpper().sle(Range.getUpper())) {
// "Range" contains "SubRange".
// L---U : Range
// L-U : SubRange
// Note that ConstantRange::contains(ConstantRange) checks unsigned,
// but we need signed checking here.
AppendRangeIfNonEmpty(Range.getLower(), SubRange.getLower());
AppendRangeIfNonEmpty(SubRange.getUpper(), Range.getUpper());
} else if (SubRange.getLower().sle(Range.getLower()) &&
Range.getUpper().sle(SubRange.getUpper())) {
// "SubRange" contains "Range".
// L-U : Range
// L---U : SubRange
continue;
} else if (Range.getLower().sge(SubRange.getLower()) &&
Range.getLower().sle(SubRange.getUpper())) {
// "Range" and "SubRange" overlap at the left.
// L---U : Range
// L---U : SubRange
AppendRangeIfNonEmpty(SubRange.getUpper(), Range.getUpper());
} else {
// "Range" and "SubRange" overlap at the right.
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add an assert for this

// L---U : Range
// L---U : SubRange
assert(SubRange.getLower().sge(Range.getLower()) &&
SubRange.getLower().sle(Range.getUpper()));
AppendRangeIfNonEmpty(Range.getLower(), SubRange.getLower());
}
}

Ranges = Result;
}

ConstantRangeList
ConstantRangeList::unionWith(const ConstantRangeList &CRL) const {
assert(getBitWidth() == CRL.getBitWidth() &&
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52 changes: 52 additions & 0 deletions llvm/unittests/IR/ConstantRangeListTest.cpp
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Expand Up @@ -101,6 +101,58 @@ ConstantRangeList GetCRL(ArrayRef<std::pair<APInt, APInt>> Pairs) {
return ConstantRangeList(Ranges);
}

TEST_F(ConstantRangeListTest, Subtract) {
APInt AP0 = APInt(64, 0, /*isSigned=*/true);
APInt AP2 = APInt(64, 2, /*isSigned=*/true);
APInt AP3 = APInt(64, 3, /*isSigned=*/true);
APInt AP4 = APInt(64, 4, /*isSigned=*/true);
APInt AP8 = APInt(64, 8, /*isSigned=*/true);
APInt AP10 = APInt(64, 10, /*isSigned=*/true);
APInt AP11 = APInt(64, 11, /*isSigned=*/true);
APInt AP12 = APInt(64, 12, /*isSigned=*/true);
ConstantRangeList CRL = GetCRL({{AP0, AP4}, {AP8, AP12}});

// Execute ConstantRangeList::subtract(ConstantRange) and check the result
// is expected. Pass "CRL" by value so that subtract() does not affect the
// argument in caller.
auto SubtractAndCheck = [](ConstantRangeList CRL,
const std::pair<int64_t, int64_t> &Range,
const ConstantRangeList &ExpectedCRL) {
CRL.subtract(ConstantRange(APInt(64, Range.first, /*isSigned=*/true),
APInt(64, Range.second, /*isSigned=*/true)));
EXPECT_EQ(CRL, ExpectedCRL);
};

// No overlap
SubtractAndCheck(CRL, {-4, 0}, CRL);
SubtractAndCheck(CRL, {4, 8}, CRL);
SubtractAndCheck(CRL, {12, 16}, CRL);

// Overlap (left, right, or both)
SubtractAndCheck(CRL, {-4, 2}, GetCRL({{AP2, AP4}, {AP8, AP12}}));
SubtractAndCheck(CRL, {-4, 4}, GetCRL({{AP8, AP12}}));
SubtractAndCheck(CRL, {-4, 8}, GetCRL({{AP8, AP12}}));
SubtractAndCheck(CRL, {0, 2}, GetCRL({{AP2, AP4}, {AP8, AP12}}));
SubtractAndCheck(CRL, {0, 4}, GetCRL({{AP8, AP12}}));
SubtractAndCheck(CRL, {0, 8}, GetCRL({{AP8, AP12}}));
SubtractAndCheck(CRL, {10, 12}, GetCRL({{AP0, AP4}, {AP8, AP10}}));
SubtractAndCheck(CRL, {8, 12}, GetCRL({{AP0, AP4}}));
SubtractAndCheck(CRL, {6, 12}, GetCRL({{AP0, AP4}}));
SubtractAndCheck(CRL, {10, 16}, GetCRL({{AP0, AP4}, {AP8, AP10}}));
SubtractAndCheck(CRL, {8, 16}, GetCRL({{AP0, AP4}}));
SubtractAndCheck(CRL, {6, 16}, GetCRL({{AP0, AP4}}));
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maybe try touching at the other ends like {0, X} and {X, 12} too
(vs {X, 4} and {8, X})?

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Done! Added another case {2, 10} that overlaps multiple ranges.

SubtractAndCheck(CRL, {2, 10}, GetCRL({{AP0, AP2}, {AP10, AP12}}));

// Subset
SubtractAndCheck(CRL, {2, 3}, GetCRL({{AP0, AP2}, {AP3, AP4}, {AP8, AP12}}));
SubtractAndCheck(CRL, {10, 11},
GetCRL({{AP0, AP4}, {AP8, AP10}, {AP11, AP12}}));

// Superset
SubtractAndCheck(CRL, {0, 12}, GetCRL({}));
SubtractAndCheck(CRL, {-4, 16}, GetCRL({}));
}

TEST_F(ConstantRangeListTest, Union) {
APInt APN4 = APInt(64, -4, /*isSigned=*/true);
APInt APN2 = APInt(64, -2, /*isSigned=*/true);
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