[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

2 files changed, 42 insertions, 50 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 13812b1175f..d50140c3b9b 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2128,54 +2128,6 @@ static Constant *computePointerICmp(const DataLayout &DL,
   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 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       // 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 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
         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 fda1dbf8825..1187de7b59b 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4081,3 +4081,43 @@ ConstantRange llvm::getConstantRangeFromMetadata(MDNode &Ranges) {
 
   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;
+}