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Add variations on: max(x,y) >= min(x,z) folds to true. This isn't that common,

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but according to my super-optimizer there are only two missed simplifications
of -instsimplify kind when compiling bzip2, and this is one of them.  It amuses
me to have bzip2 be perfectly optimized as far as instsimplify goes!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130840 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands
2011-05-04 16:05:05 +00:00
parent 269687fa35
commit 8140ad32ce
2 changed files with 134 additions and 2 deletions
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48
lib/Analysis/InstructionSimplify.cpp
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@ -1873,7 +1873,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE;
CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B".
// Signed max/min.
// Signed variants on "max(a,b)>=a -> true".
if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
if (A != RHS) std::swap(A, B); // smax(A, B) pred A.
EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B".
@ -1929,7 +1929,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
// Unsigned max/min.
// Unsigned variants on "max(a,b)>=a -> true".
P = CmpInst::BAD_ICMP_PREDICATE;
if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
if (A != RHS) std::swap(A, B); // umax(A, B) pred A.
@ -1986,6 +1986,50 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
// Variants on "max(x,y) >= min(x,z)".
Value *C, *D;
if (match(LHS, m_SMax(m_Value(A), m_Value(B))) &&
match(RHS, m_SMin(m_Value(C), m_Value(D))) &&
(A == C || A == D || B == C || B == D)) {
// max(x, ?) pred min(x, ?).
if (Pred == CmpInst::ICMP_SGE)
// Always true.
return Constant::getAllOnesValue(ITy);
if (Pred == CmpInst::ICMP_SLT)
// Always false.
return Constant::getNullValue(ITy);
} else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) &&
match(RHS, m_SMax(m_Value(C), m_Value(D))) &&
(A == C || A == D || B == C || B == D)) {
// min(x, ?) pred max(x, ?).
if (Pred == CmpInst::ICMP_SLE)
// Always true.
return Constant::getAllOnesValue(ITy);
if (Pred == CmpInst::ICMP_SGT)
// Always false.
return Constant::getNullValue(ITy);
} else if (match(LHS, m_UMax(m_Value(A), m_Value(B))) &&
match(RHS, m_UMin(m_Value(C), m_Value(D))) &&
(A == C || A == D || B == C || B == D)) {
// max(x, ?) pred min(x, ?).
if (Pred == CmpInst::ICMP_UGE)
// Always true.
return Constant::getAllOnesValue(ITy);
if (Pred == CmpInst::ICMP_ULT)
// Always false.
return Constant::getNullValue(ITy);
} else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) &&
match(RHS, m_UMax(m_Value(C), m_Value(D))) &&
(A == C || A == D || B == C || B == D)) {
// min(x, ?) pred max(x, ?).
if (Pred == CmpInst::ICMP_ULE)
// Always true.
return Constant::getAllOnesValue(ITy);
if (Pred == CmpInst::ICMP_UGT)
// Always false.
return Constant::getNullValue(ITy);
}
// If the comparison is with the result of a select instruction, check whether
// comparing with either branch of the select always yields the same value.
if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))