Add variations on: max(x,y) >= min(x,z) folds to true. This isn't that common,
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
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 3028f17..e7ef6ff 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -1873,7 +1873,7 @@
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 @@
}
}
- // 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 @@
}
}
+ // 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))