Reverting r215966, r215965, r215964, r215963, r215960, r215959, r215958, and r215957...

[oota-llvm.git] / lib / Analysis / InstructionSimplify.cpp

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 6ac1ae8d5ed1783a66b035fcb5061f47f1c9b709..459fc92bce1a856a2d621b6aedc24c76c18c2d1a 100644 (file)
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -676,6 +676,18 @@ static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
   if (Op0 == Op1)
     return Constant::getNullValue(Op0->getType());
 
+  // X - (0 - Y) -> X if the second sub is NUW.
+  // If Y != 0, 0 - Y is a poison value.
+  // If Y == 0, 0 - Y simplifies to 0.
+  if (BinaryOperator::isNeg(Op1)) {
+    if (const auto *BO = dyn_cast<BinaryOperator>(Op1)) {
+      assert(BO->getOpcode() == Instruction::Sub &&
+             "Expected a subtraction operator!");
+      if (BO->hasNoUnsignedWrap())
+        return Op0;
+    }
+  }
+
   // (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies.
   // For example, (X + Y) - Y -> X; (Y + X) - Y -> X
   Value *X = nullptr, *Y = nullptr, *Z = Op1;
@@ -1347,7 +1359,7 @@ static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
     return X;
 
   // Arithmetic shifting an all-sign-bit value is a no-op.
-  unsigned NumSignBits = ComputeNumSignBits(Op0);
+  unsigned NumSignBits = ComputeNumSignBits(Op0, Q.DL);
   if (NumSignBits == Op0->getType()->getScalarSizeInBits())
     return Op0;