[Value Tracking] Refactor icmp comparison logic into helper. NFC.

llvm-svn: 309417

1 files changed, 62 insertions, 41 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 9fbc09cb71e..a274f413c69 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4384,6 +4384,51 @@ isImpliedCondMatchingImmOperands(CmpInst::Predicate APred, const Value *ALHS,
   return None;
 }
 
+/// Return true if LHS implies RHS is true.  Return false if LHS implies RHS is
+/// false.  Otherwise, return None if we can't infer anything.
+static Optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
+                                         const ICmpInst *RHS,
+                                         const DataLayout &DL, bool LHSIsFalse,
+                                         unsigned Depth) {
+  Value *ALHS = LHS->getOperand(0);
+  Value *ARHS = LHS->getOperand(1);
+  // The rest of the logic assumes the LHS condition is true.  If that's not the
+  // case, invert the predicate to make it so.
+  ICmpInst::Predicate APred =
+      LHSIsFalse ? LHS->getInversePredicate() : LHS->getPredicate();
+
+  Value *BLHS = RHS->getOperand(0);
+  Value *BRHS = RHS->getOperand(1);
+  ICmpInst::Predicate BPred = RHS->getPredicate();
+
+  // Can we infer anything when the two compares have matching operands?
+  bool IsSwappedOps;
+  if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, IsSwappedOps)) {
+    if (Optional<bool> Implication = isImpliedCondMatchingOperands(
+            APred, ALHS, ARHS, BPred, BLHS, BRHS, IsSwappedOps))
+      return Implication;
+    // No amount of additional analysis will infer the second condition, so
+    // early exit.
+    return None;
+  }
+
+  // Can we infer anything when the LHS operands match and the RHS operands are
+  // constants (not necessarily matching)?
+  if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
+    if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
+            APred, ALHS, cast<ConstantInt>(ARHS), BPred, BLHS,
+            cast<ConstantInt>(BRHS)))
+      return Implication;
+    // No amount of additional analysis will infer the second condition, so
+    // early exit.
+    return None;
+  }
+
+  if (APred == BPred)
+    return isImpliedCondOperands(APred, ALHS, ARHS, BLHS, BRHS, DL, Depth);
+  return None;
+}
+
 Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
                                         const DataLayout &DL, bool LHSIsFalse,
                                         unsigned Depth) {
@@ -4403,22 +4448,32 @@ Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
     return None;
   assert(OpTy->isIntegerTy(1) && "implied by above");
 
-  Value *BLHS, *BRHS;
-  ICmpInst::Predicate BPred;
   // We expect the RHS to be an icmp.
-  if (!match(RHS, m_ICmp(BPred, m_Value(BLHS), m_Value(BRHS))))
+  if (!isa<ICmpInst>(RHS))
+    return None;
+
+  // Both LHS and RHS are icmps.
+  if (isa<ICmpInst>(LHS))
+    return isImpliedCondICmps(cast<ICmpInst>(LHS), cast<ICmpInst>(RHS), DL,
+                              LHSIsFalse, Depth);
+
+  // The LHS can be an 'or' or an 'and' instruction.
+  const Instruction *LHSInst = dyn_cast<Instruction>(LHS);
+  if (!LHSInst)
     return None;
 
-  Value *ALHS, *ARHS;
-  ICmpInst::Predicate APred;
-  // The LHS can be an 'or', 'and', or 'icmp'.
-  if (!match(LHS, m_ICmp(APred, m_Value(ALHS), m_Value(ARHS)))) {
+  switch (LHSInst->getOpcode()) {
+  default:
+    return None;
+  case Instruction::Or:
+  case Instruction::And: {
     // The remaining tests are all recursive, so bail out if we hit the limit.
     if (Depth == MaxDepth)
       return None;
     // If the result of an 'or' is false, then we know both legs of the 'or' are
     // false.  Similarly, if the result of an 'and' is true, then we know both
     // legs of the 'and' are true.
+    Value *ALHS, *ARHS;
     if ((LHSIsFalse && match(LHS, m_Or(m_Value(ALHS), m_Value(ARHS)))) ||
         (!LHSIsFalse && match(LHS, m_And(m_Value(ALHS), m_Value(ARHS))))) {
       if (Optional<bool> Implication =
@@ -4431,39 +4486,5 @@ Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
     }
     return None;
   }
-  // All of the below logic assumes both LHS and RHS are icmps.
-  assert(isa<ICmpInst>(LHS) && isa<ICmpInst>(RHS) && "Expected icmps.");
-
-  // The rest of the logic assumes the LHS condition is true.  If that's not the
-  // case, invert the predicate to make it so.
-  if (LHSIsFalse)
-    APred = CmpInst::getInversePredicate(APred);
-
-  // Can we infer anything when the two compares have matching operands?
-  bool IsSwappedOps;
-  if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, IsSwappedOps)) {
-    if (Optional<bool> Implication = isImpliedCondMatchingOperands(
-            APred, ALHS, ARHS, BPred, BLHS, BRHS, IsSwappedOps))
-      return Implication;
-    // No amount of additional analysis will infer the second condition, so
-    // early exit.
-    return None;
-  }
-
-  // Can we infer anything when the LHS operands match and the RHS operands are
-  // constants (not necessarily matching)?
-  if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
-    if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
-            APred, ALHS, cast<ConstantInt>(ARHS), BPred, BLHS,
-            cast<ConstantInt>(BRHS)))
-      return Implication;
-    // No amount of additional analysis will infer the second condition, so
-    // early exit.
-    return None;
   }
-
-  if (APred == BPred)
-    return isImpliedCondOperands(APred, ALHS, ARHS, BLHS, BRHS, DL, Depth);
-
-  return None;
 }