[InstCombine] Make (X|C1)^C2 -> X^(C1^C2) iff X&~C1 == 0 work for splat vectors

This also corrects the description to match what was actually implemented. The old comment said X^(C1|C2), but it implemented X^((C1|C2)&~(C1&C2)). I believe ((C1|C2)&~(C1&C2)) is equivalent to (C1^C2).

Differential Revision: https://reviews.llvm.org/D36505

llvm-svn: 310658

1 files changed, 18 insertions, 23 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index bc8b0496ec7..5a13bbce835 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2365,53 +2365,48 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
   {
     const APInt *RHSC;
     if (match(Op1, m_APInt(RHSC))) {
-      Value *V;
+      Value *X;
       const APInt *C;
-      if (match(Op0, m_Sub(m_APInt(C), m_Value(V)))) {
+      if (match(Op0, m_Sub(m_APInt(C), m_Value(X)))) {
         // ~(c-X) == X-c-1 == X+(-c-1)
         if (RHSC->isAllOnesValue()) {
           Constant *NewC = ConstantInt::get(I.getType(), -(*C) - 1);
-          return BinaryOperator::CreateAdd(V, NewC);
+          return BinaryOperator::CreateAdd(X, NewC);
         }
         if (RHSC->isSignMask()) {
           // (C - X) ^ signmask -> (C + signmask - X)
           Constant *NewC = ConstantInt::get(I.getType(), *C + *RHSC);
-          return BinaryOperator::CreateSub(NewC, V);
+          return BinaryOperator::CreateSub(NewC, X);
         }
-      } else if (match(Op0, m_Add(m_Value(V), m_APInt(C)))) {
+      } else if (match(Op0, m_Add(m_Value(X), m_APInt(C)))) {
         // ~(X-c) --> (-c-1)-X
         if (RHSC->isAllOnesValue()) {
           Constant *NewC = ConstantInt::get(I.getType(), -(*C) - 1);
-          return BinaryOperator::CreateSub(NewC, V);
+          return BinaryOperator::CreateSub(NewC, X);
         }
         if (RHSC->isSignMask()) {
           // (X + C) ^ signmask -> (X + C + signmask)
           Constant *NewC = ConstantInt::get(I.getType(), *C + *RHSC);
-          return BinaryOperator::CreateAdd(V, NewC);
+          return BinaryOperator::CreateAdd(X, NewC);
         }
       }
+
+      // (X|C1)^C2 -> X^(C1^C2) iff X&~C1 == 0
+      if (match(Op0, m_Or(m_Value(X), m_APInt(C))) &&
+          MaskedValueIsZero(X, *C, 0, &I)) {
+        Constant *NewC = ConstantInt::get(I.getType(), *C ^ *RHSC);
+        Worklist.Add(cast<Instruction>(Op0));
+        I.setOperand(0, X);
+        I.setOperand(1, NewC);
+        return &I;
+      }
     }
   }
 
   if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1)) {
     if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
       if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
-        if (Op0I->getOpcode() == Instruction::Or) {
-          // (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
-          if (MaskedValueIsZero(Op0I->getOperand(0), Op0CI->getValue(),
-                                0, &I)) {
-            Constant *NewRHS = ConstantExpr::getOr(Op0CI, RHSC);
-            // Anything in both C1 and C2 is known to be zero, remove it from
-            // NewRHS.
-            Constant *CommonBits = ConstantExpr::getAnd(Op0CI, RHSC);
-            NewRHS = ConstantExpr::getAnd(NewRHS,
-                                       ConstantExpr::getNot(CommonBits));
-            Worklist.Add(Op0I);
-            I.setOperand(0, Op0I->getOperand(0));
-            I.setOperand(1, NewRHS);
-            return &I;
-          }
-        } else if (Op0I->getOpcode() == Instruction::LShr) {
+        if (Op0I->getOpcode() == Instruction::LShr) {
           // ((X^C1) >> C2) ^ C3 -> (X>>C2) ^ ((C1>>C2)^C3)
           // E1 = "X ^ C1"
           BinaryOperator *E1;