[ValueTracking] Expose `implies` via ValueTracking, NFC
Summary: This will allow a later patch to `JumpThreading` use this functionality.
Reviewers: reames
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13971
llvm-svn: 251488
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 13812b1..d50140c 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2128,54 +2128,6 @@
return nullptr;
}
-/// Return true if B is known to be implied by A. A & B must be i1 (boolean)
-/// values or a vector of such values. Note that the truth table for
-/// implication is the same as <=u on i1 values (but not <=s!). The truth
-/// table for both is:
-/// | T | F (B)
-/// T | T | F
-/// F | T | T
-/// (A)
-static bool implies(Value *A, Value *B) {
- assert(A->getType() == B->getType() && "mismatched type");
- Type *OpTy = A->getType();
- assert(OpTy->getScalarType()->isIntegerTy(1));
-
- // A ==> A by definition
- if (A == B) return true;
-
- if (OpTy->isVectorTy())
- // TODO: extending the code below to handle vectors
- return false;
- assert(OpTy->isIntegerTy(1) && "implied by above");
-
- ICmpInst::Predicate APred, BPred;
- Value *I;
- Value *L;
- ConstantInt *CI;
- // i +_{nsw} C_{>0} <s L ==> i <s L
- if (match(A, m_ICmp(APred,
- m_NSWAdd(m_Value(I), m_ConstantInt(CI)),
- m_Value(L))) &&
- APred == ICmpInst::ICMP_SLT &&
- !CI->isNegative() &&
- match(B, m_ICmp(BPred, m_Specific(I), m_Specific(L))) &&
- BPred == ICmpInst::ICMP_SLT)
- return true;
-
- // i +_{nuw} C_{>0} <u L ==> i <u L
- if (match(A, m_ICmp(APred,
- m_NUWAdd(m_Value(I), m_ConstantInt(CI)),
- m_Value(L))) &&
- APred == ICmpInst::ICMP_ULT &&
- !CI->isNegative() &&
- match(B, m_ICmp(BPred, m_Specific(I), m_Specific(L))) &&
- BPred == ICmpInst::ICMP_ULT)
- return true;
-
- return false;
-}
-
/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
@@ -2224,7 +2176,7 @@
// X >=u 1 -> X
if (match(RHS, m_One()))
return LHS;
- if (implies(RHS, LHS))
+ if (isImpliedCondition(RHS, LHS))
return getTrue(ITy);
break;
case ICmpInst::ICMP_SLT:
@@ -2238,7 +2190,7 @@
return LHS;
break;
case ICmpInst::ICMP_ULE:
- if (implies(LHS, RHS))
+ if (isImpliedCondition(LHS, RHS))
return getTrue(ITy);
break;
}
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index fda1dbf..1187de7 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4081,3 +4081,43 @@
return CR;
}
+
+bool llvm::isImpliedCondition(Value *LHS, Value *RHS) {
+ assert(LHS->getType() == RHS->getType() && "mismatched type");
+ Type *OpTy = LHS->getType();
+ assert(OpTy->getScalarType()->isIntegerTy(1));
+
+ // LHS ==> RHS by definition
+ if (LHS == RHS) return true;
+
+ if (OpTy->isVectorTy())
+ // TODO: extending the code below to handle vectors
+ return false;
+ assert(OpTy->isIntegerTy(1) && "implied by above");
+
+ ICmpInst::Predicate APred, BPred;
+ Value *I;
+ Value *L;
+ ConstantInt *CI;
+ // i +_{nsw} C_{>0} <s L ==> i <s L
+ if (match(LHS, m_ICmp(APred,
+ m_NSWAdd(m_Value(I), m_ConstantInt(CI)),
+ m_Value(L))) &&
+ APred == ICmpInst::ICMP_SLT &&
+ !CI->isNegative() &&
+ match(RHS, m_ICmp(BPred, m_Specific(I), m_Specific(L))) &&
+ BPred == ICmpInst::ICMP_SLT)
+ return true;
+
+ // i +_{nuw} C_{>0} <u L ==> i <u L
+ if (match(LHS, m_ICmp(APred,
+ m_NUWAdd(m_Value(I), m_ConstantInt(CI)),
+ m_Value(L))) &&
+ APred == ICmpInst::ICMP_ULT &&
+ !CI->isNegative() &&
+ match(RHS, m_ICmp(BPred, m_Specific(I), m_Specific(L))) &&
+ BPred == ICmpInst::ICMP_ULT)
+ return true;
+
+ return false;
+}