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[ValueTracking] Change if-else chain into switch in computeKnownBitsFromAssume 

This is a follow-up patch to D60504 to further improve
performance issues in computeKnownBitsFromAssume.
    
The patch is NFC, but may improve compile-time performance
if the compiler isn't clever enough to do the optimization
itself.

llvm-svn: 358163
This commit is contained in:
Sander de Smalen 2019-04-11 13:02:19 +00:00
parent 6fa145e429
commit 4f5d2df48d
1 changed files with 18 additions and 8 deletions
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26
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -625,7 +625,10 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
CmpInst::Predicate Pred;
uint64_t C;
if (Cmp->getPredicate() == ICmpInst::ICMP_EQ) {
switch (Cmp->getPredicate()) {
default:
break;
case ICmpInst::ICMP_EQ:
// assume(v = a)
if (match(Cmp, m_c_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -762,7 +765,8 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
Known.Zero |= RHSKnown.One << C;
Known.One |= RHSKnown.Zero << C;
}
} else if (Cmp->getPredicate() == ICmpInst::ICMP_SGE) {
break;
case ICmpInst::ICMP_SGE:
// assume(v >=_s c) where c is non-negative
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -774,7 +778,8 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
Known.makeNonNegative();
}
}
} else if (Cmp->getPredicate() == ICmpInst::ICMP_SGT) {
break;
case ICmpInst::ICMP_SGT:
// assume(v >_s c) where c is at least -1.
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -786,7 +791,8 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
Known.makeNonNegative();
}
}
} else if (Cmp->getPredicate() == ICmpInst::ICMP_SLE) {
break;
case ICmpInst::ICMP_SLE:
// assume(v <=_s c) where c is negative
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -798,7 +804,8 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
Known.makeNegative();
}
}
} else if (Cmp->getPredicate() == ICmpInst::ICMP_SLT) {
break;
case ICmpInst::ICMP_SLT:
// assume(v <_s c) where c is non-positive
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -810,8 +817,9 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
Known.makeNegative();
}
}
// assume(v <=_u c)
} else if (Cmp->getPredicate() == ICmpInst::ICMP_ULE) {
break;
case ICmpInst::ICMP_ULE:
// assume(v <=_u c)
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown(BitWidth);
@ -820,8 +828,9 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
// Whatever high bits in c are zero are known to be zero.
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
}
break;
case ICmpInst::ICMP_ULT:
// assume(v <_u c)
} else if (Cmp->getPredicate() == ICmpInst::ICMP_ULT) {
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown(BitWidth);
@ -842,6 +851,7 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
else
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
}
break;
}
}