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[DA] Extract duplicated logic from exactSIVtest and exactRDIVtest (NFC) (#152712)
This patch refactors `exactSIVtest` and `exactRDIVtest` by consolidating duplicated logic into a single function. Same as #152688, the main goal is to improve code maintainability, since extra validation logic (as written in TODO comments) may be necessary.
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‎llvm/lib/Analysis/DependenceAnalysis.cpp‎

Lines changed: 113 additions & 82 deletions
Original file line numberDiff line numberDiff line change
@@ -1531,6 +1531,62 @@ static APInt ceilingOfQuotient(const APInt &A, const APInt &B) {
15311531
return Q;
15321532
}
15331533

1534+
/// Given an affine expression of the form A*k + B, where k is an arbitrary
1535+
/// integer, infer the possible range of k based on the known range of the
1536+
/// affine expression. If we know A*k + B is non-negative, i.e.,
1537+
///
1538+
/// A*k + B >= 0
1539+
///
1540+
/// we can derive the following inequalities for k when A is positive:
1541+
///
1542+
/// k >= -B / A
1543+
///
1544+
/// Since k is an integer, it means k is greater than or equal to the
1545+
/// ceil(-B / A).
1546+
///
1547+
/// If the upper bound of the affine expression \p UB is passed, the following
1548+
/// inequality can be derived as well:
1549+
///
1550+
/// A*k + B <= UB
1551+
///
1552+
/// which leads to:
1553+
///
1554+
/// k <= (UB - B) / A
1555+
///
1556+
/// Again, as k is an integer, it means k is less than or equal to the
1557+
/// floor((UB - B) / A).
1558+
///
1559+
/// The similar logic applies when A is negative, but the inequalities sign flip
1560+
/// while working with them.
1561+
///
1562+
/// Preconditions: \p A is non-zero, and we know A*k + B is non-negative.
1563+
static std::pair<std::optional<APInt>, std::optional<APInt>>
1564+
inferDomainOfAffine(const APInt &A, const APInt &B,
1565+
const std::optional<APInt> &UB) {
1566+
assert(A != 0 && "A must be non-zero");
1567+
std::optional<APInt> TL, TU;
1568+
if (A.sgt(0)) {
1569+
TL = ceilingOfQuotient(-B, A);
1570+
LLVM_DEBUG(dbgs() << "\t Possible TL = " << *TL << "\n");
1571+
// New bound check - modification to Banerjee's e3 check
1572+
if (UB) {
1573+
// TODO?: Overflow check for UB - B
1574+
TU = floorOfQuotient(*UB - B, A);
1575+
LLVM_DEBUG(dbgs() << "\t Possible TU = " << *TU << "\n");
1576+
}
1577+
} else {
1578+
TU = floorOfQuotient(-B, A);
1579+
LLVM_DEBUG(dbgs() << "\t Possible TU = " << *TU << "\n");
1580+
// New bound check - modification to Banerjee's e3 check
1581+
if (UB) {
1582+
// TODO?: Overflow check for UB - B
1583+
TL = ceilingOfQuotient(*UB - B, A);
1584+
LLVM_DEBUG(dbgs() << "\t Possible TL = " << *TL << "\n");
1585+
}
1586+
}
1587+
return std::make_pair(TL, TU);
1588+
}
1589+
15341590
// exactSIVtest -
15351591
// When we have a pair of subscripts of the form [c1 + a1*i] and [c2 + a2*i],
15361592
// where i is an induction variable, c1 and c2 are loop invariant, and a1
@@ -1590,14 +1646,12 @@ bool DependenceInfo::exactSIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
15901646
LLVM_DEBUG(dbgs() << "\t X = " << X << ", Y = " << Y << "\n");
15911647

15921648
// since SCEV construction normalizes, LM = 0
1593-
APInt UM(Bits, 1, true);
1594-
bool UMValid = false;
1649+
std::optional<APInt> UM;
15951650
// UM is perhaps unavailable, let's check
15961651
if (const SCEVConstant *CUB =
15971652
collectConstantUpperBound(CurLoop, Delta->getType())) {
15981653
UM = CUB->getAPInt();
1599-
LLVM_DEBUG(dbgs() << "\t UM = " << UM << "\n");
1600-
UMValid = true;
1654+
LLVM_DEBUG(dbgs() << "\t UM = " << *UM << "\n");
16011655
}
16021656

16031657
APInt TU(APInt::getSignedMaxValue(Bits));
@@ -1609,44 +1663,33 @@ bool DependenceInfo::exactSIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
16091663
LLVM_DEBUG(dbgs() << "\t TX = " << TX << "\n");
16101664
LLVM_DEBUG(dbgs() << "\t TY = " << TY << "\n");
16111665

1612-
SmallVector<APInt, 2> TLVec, TUVec;
16131666
APInt TB = BM.sdiv(G);
1614-
if (TB.sgt(0)) {
1615-
TLVec.push_back(ceilingOfQuotient(-TX, TB));
1616-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
1617-
// New bound check - modification to Banerjee's e3 check
1618-
if (UMValid) {
1619-
TUVec.push_back(floorOfQuotient(UM - TX, TB));
1620-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
1621-
}
1622-
} else {
1623-
TUVec.push_back(floorOfQuotient(-TX, TB));
1624-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
1625-
// New bound check - modification to Banerjee's e3 check
1626-
if (UMValid) {
1627-
TLVec.push_back(ceilingOfQuotient(UM - TX, TB));
1628-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
1629-
}
1630-
}
1631-
16321667
APInt TA = AM.sdiv(G);
1633-
if (TA.sgt(0)) {
1634-
if (UMValid) {
1635-
TUVec.push_back(floorOfQuotient(UM - TY, TA));
1636-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
1637-
}
1638-
// New bound check - modification to Banerjee's e3 check
1639-
TLVec.push_back(ceilingOfQuotient(-TY, TA));
1640-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
1641-
} else {
1642-
if (UMValid) {
1643-
TLVec.push_back(ceilingOfQuotient(UM - TY, TA));
1644-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
1645-
}
1646-
// New bound check - modification to Banerjee's e3 check
1647-
TUVec.push_back(floorOfQuotient(-TY, TA));
1648-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
1649-
}
1668+
1669+
// At this point, we have the following equations:
1670+
//
1671+
// TA*i0 - TB*i1 = TC
1672+
//
1673+
// Also, we know that the all pairs of (i0, i1) can be expressed as:
1674+
//
1675+
// (TX + k*TB, TY + k*TA)
1676+
//
1677+
// where k is an arbitrary integer.
1678+
auto [TL0, TU0] = inferDomainOfAffine(TB, TX, UM);
1679+
auto [TL1, TU1] = inferDomainOfAffine(TA, TY, UM);
1680+
1681+
auto CreateVec = [](const std::optional<APInt> &V0,
1682+
const std::optional<APInt> &V1) {
1683+
SmallVector<APInt, 2> Vec;
1684+
if (V0)
1685+
Vec.push_back(*V0);
1686+
if (V1)
1687+
Vec.push_back(*V1);
1688+
return Vec;
1689+
};
1690+
1691+
SmallVector<APInt, 2> TLVec = CreateVec(TL0, TL1);
1692+
SmallVector<APInt, 2> TUVec = CreateVec(TU0, TU1);
16501693

16511694
LLVM_DEBUG(dbgs() << "\t TA = " << TA << "\n");
16521695
LLVM_DEBUG(dbgs() << "\t TB = " << TB << "\n");
@@ -1967,24 +2010,20 @@ bool DependenceInfo::exactRDIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
19672010
LLVM_DEBUG(dbgs() << "\t X = " << X << ", Y = " << Y << "\n");
19682011

19692012
// since SCEV construction seems to normalize, LM = 0
1970-
APInt SrcUM(Bits, 1, true);
1971-
bool SrcUMvalid = false;
2013+
std::optional<APInt> SrcUM;
19722014
// SrcUM is perhaps unavailable, let's check
19732015
if (const SCEVConstant *UpperBound =
19742016
collectConstantUpperBound(SrcLoop, Delta->getType())) {
19752017
SrcUM = UpperBound->getAPInt();
1976-
LLVM_DEBUG(dbgs() << "\t SrcUM = " << SrcUM << "\n");
1977-
SrcUMvalid = true;
2018+
LLVM_DEBUG(dbgs() << "\t SrcUM = " << *SrcUM << "\n");
19782019
}
19792020

1980-
APInt DstUM(Bits, 1, true);
1981-
bool DstUMvalid = false;
2021+
std::optional<APInt> DstUM;
19822022
// UM is perhaps unavailable, let's check
19832023
if (const SCEVConstant *UpperBound =
19842024
collectConstantUpperBound(DstLoop, Delta->getType())) {
19852025
DstUM = UpperBound->getAPInt();
1986-
LLVM_DEBUG(dbgs() << "\t DstUM = " << DstUM << "\n");
1987-
DstUMvalid = true;
2026+
LLVM_DEBUG(dbgs() << "\t DstUM = " << *DstUM << "\n");
19882027
}
19892028

19902029
APInt TU(APInt::getSignedMaxValue(Bits));
@@ -1996,47 +2035,39 @@ bool DependenceInfo::exactRDIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
19962035
LLVM_DEBUG(dbgs() << "\t TX = " << TX << "\n");
19972036
LLVM_DEBUG(dbgs() << "\t TY = " << TY << "\n");
19982037

1999-
SmallVector<APInt, 2> TLVec, TUVec;
20002038
APInt TB = BM.sdiv(G);
2001-
if (TB.sgt(0)) {
2002-
TLVec.push_back(ceilingOfQuotient(-TX, TB));
2003-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
2004-
if (SrcUMvalid) {
2005-
TUVec.push_back(floorOfQuotient(SrcUM - TX, TB));
2006-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
2007-
}
2008-
} else {
2009-
TUVec.push_back(floorOfQuotient(-TX, TB));
2010-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
2011-
if (SrcUMvalid) {
2012-
TLVec.push_back(ceilingOfQuotient(SrcUM - TX, TB));
2013-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
2014-
}
2015-
}
2016-
20172039
APInt TA = AM.sdiv(G);
2018-
if (TA.sgt(0)) {
2019-
TLVec.push_back(ceilingOfQuotient(-TY, TA));
2020-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
2021-
if (DstUMvalid) {
2022-
TUVec.push_back(floorOfQuotient(DstUM - TY, TA));
2023-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
2024-
}
2025-
} else {
2026-
TUVec.push_back(floorOfQuotient(-TY, TA));
2027-
LLVM_DEBUG(dbgs() << "\t Possible TU = " << TUVec.back() << "\n");
2028-
if (DstUMvalid) {
2029-
TLVec.push_back(ceilingOfQuotient(DstUM - TY, TA));
2030-
LLVM_DEBUG(dbgs() << "\t Possible TL = " << TLVec.back() << "\n");
2031-
}
2032-
}
20332040

2034-
if (TLVec.empty() || TUVec.empty())
2035-
return false;
2041+
// At this point, we have the following equations:
2042+
//
2043+
// TA*i - TB*j = TC
2044+
//
2045+
// Also, we know that the all pairs of (i, j) can be expressed as:
2046+
//
2047+
// (TX + k*TB, TY + k*TA)
2048+
//
2049+
// where k is an arbitrary integer.
2050+
auto [TL0, TU0] = inferDomainOfAffine(TB, TX, SrcUM);
2051+
auto [TL1, TU1] = inferDomainOfAffine(TA, TY, DstUM);
20362052

20372053
LLVM_DEBUG(dbgs() << "\t TA = " << TA << "\n");
20382054
LLVM_DEBUG(dbgs() << "\t TB = " << TB << "\n");
20392055

2056+
auto CreateVec = [](const std::optional<APInt> &V0,
2057+
const std::optional<APInt> &V1) {
2058+
SmallVector<APInt, 2> Vec;
2059+
if (V0)
2060+
Vec.push_back(*V0);
2061+
if (V1)
2062+
Vec.push_back(*V1);
2063+
return Vec;
2064+
};
2065+
2066+
SmallVector<APInt, 2> TLVec = CreateVec(TL0, TL1);
2067+
SmallVector<APInt, 2> TUVec = CreateVec(TU0, TU1);
2068+
if (TLVec.empty() || TUVec.empty())
2069+
return false;
2070+
20402071
TL = APIntOps::smax(TLVec.front(), TLVec.back());
20412072
TU = APIntOps::smin(TUVec.front(), TUVec.back());
20422073
LLVM_DEBUG(dbgs() << "\t TL = " << TL << "\n");

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