[ValueTracking][InstSimplify] Move abs handling into computeConstantRange(); NFC

This is preparation for D59506. The InstructionSimplify abs handling
is moved into computeConstantRange(), which is the general place for
such calculations. This is NFC and doesn't affect the existing tests
in test/Transforms/InstSimplify/icmp-abs-nabs.ll.

Differential Revision: https://reviews.llvm.org/D59511

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356409 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 16c0b51a380c307b1cfee79fa55382bdf9505a73..1c839fed171e266be5190fa6c92ff6f6f82d2992 100644 (file)
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -2826,44 +2826,6 @@ static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
   return nullptr;
 }
 
-static Value *simplifyICmpWithAbsNabs(CmpInst::Predicate Pred, Value *Op0,
-                                      Value *Op1) {
-  // We need a comparison with a constant.
-  const APInt *C;
-  if (!match(Op1, m_APInt(C)))
-    return nullptr;
-
-  // matchSelectPattern returns the negation part of an abs pattern in SP1.
-  // If the negate has an NSW flag, abs(INT_MIN) is undefined. Without that
-  // constraint, we can't make a contiguous range for the result of abs.
-  ICmpInst::Predicate AbsPred = ICmpInst::BAD_ICMP_PREDICATE;
-  Value *SP0, *SP1;
-  SelectPatternFlavor SPF = matchSelectPattern(Op0, SP0, SP1).Flavor;
-  if (SPF == SelectPatternFlavor::SPF_ABS &&
-      cast<Instruction>(SP1)->hasNoSignedWrap())
-    // The result of abs(X) is >= 0 (with nsw).
-    AbsPred = ICmpInst::ICMP_SGE;
-  if (SPF == SelectPatternFlavor::SPF_NABS)
-    // The result of -abs(X) is <= 0.
-    AbsPred = ICmpInst::ICMP_SLE;
-
-  if (AbsPred == ICmpInst::BAD_ICMP_PREDICATE)
-    return nullptr;
-
-  // If there is no intersection between abs/nabs and the range of this icmp,
-  // the icmp must be false. If the abs/nabs range is a subset of the icmp
-  // range, the icmp must be true.
-  APInt Zero = APInt::getNullValue(C->getBitWidth());
-  ConstantRange AbsRange = ConstantRange::makeExactICmpRegion(AbsPred, Zero);
-  ConstantRange CmpRange = ConstantRange::makeExactICmpRegion(Pred, *C);
-  if (AbsRange.intersectWith(CmpRange).isEmptySet())
-    return getFalse(GetCompareTy(Op0));
-  if (CmpRange.contains(AbsRange))
-    return getTrue(GetCompareTy(Op0));
-
-  return nullptr;
-}
-
 /// Simplify integer comparisons where at least one operand of the compare
 /// matches an integer min/max idiom.
 static Value *simplifyICmpWithMinMax(CmpInst::Predicate Pred, Value *LHS,
@@ -3295,9 +3257,6 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   if (Value *V = simplifyICmpWithMinMax(Pred, LHS, RHS, Q, MaxRecurse))
     return V;
 
-  if (Value *V = simplifyICmpWithAbsNabs(Pred, LHS, RHS))
-    return V;
-
   // Simplify comparisons of related pointers using a powerful, recursive
   // GEP-walk when we have target data available..
   if (LHS->getType()->isPointerTy())

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index ca56ec653d6ad98f66c437bbcf2a93132dd58475..00123788f2f8848e86e139059e65d3fa391f5e18 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -5653,6 +5653,36 @@ static void setLimitsForIntrinsic(const IntrinsicInst &II, APInt &Lower,
   }
 }
 
+static void setLimitsForSelectPattern(const SelectInst &SI, APInt &Lower,
+                                      APInt &Upper) {
+  const Value *LHS, *RHS;
+  SelectPatternResult R = matchSelectPattern(&SI, LHS, RHS);
+  if (R.Flavor == SPF_UNKNOWN)
+    return;
+
+  unsigned BitWidth = SI.getType()->getScalarSizeInBits();
+
+  // matchSelectPattern() returns the negation part of an abs pattern in RHS.
+  // If the negate has an NSW flag, abs(INT_MIN) is undefined. Without that
+  // constraint, we can't make a contiguous range for the result of abs.
+  if (R.Flavor == SelectPatternFlavor::SPF_ABS &&
+      cast<Instruction>(RHS)->hasNoSignedWrap()) {
+    // The result of abs(X) is >= 0 (with nsw).
+    Lower = APInt::getNullValue(BitWidth);
+    Upper = APInt::getSignedMaxValue(BitWidth) + 1;
+    return;
+  }
+
+  if (R.Flavor == SelectPatternFlavor::SPF_NABS) {
+    // The result of -abs(X) is <= 0.
+    Lower = APInt::getSignedMinValue(BitWidth);
+    Upper = APInt(BitWidth, 1);
+    return;
+  }
+
+  // TODO Handle min/max flavors.
+}
+
 ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) {
   assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction");
 
@@ -5664,6 +5694,8 @@ ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) {
     setLimitsForBinOp(*BO, Lower, Upper, IIQ);
   else if (auto *II = dyn_cast<IntrinsicInst>(V))
     setLimitsForIntrinsic(*II, Lower, Upper);
+  else if (auto *SI = dyn_cast<SelectInst>(V))
+    setLimitsForSelectPattern(*SI, Lower, Upper);
 
   ConstantRange CR = Lower != Upper ? ConstantRange(Lower, Upper)
                                     : ConstantRange(BitWidth, true);