[InstCombine] add/move folds for [not]-xor

We handled all of the commuted variants for plain xor already,
although they were scattered around and sometimes folded less
efficiently using distributive laws. We had no folds for not-xor.

Handling all of these patterns consistently is part of trying to 
reinstate:
https://reviews.llvm.org/rL300977

llvm-svn: 301144

1 files changed, 67 insertions, 38 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 17a6fb9a402..dccc3115463 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1234,6 +1234,56 @@ static Instruction *foldBoolSextMaskToSelect(BinaryOperator &I) {
   return nullptr;
 }
 
+static Instruction *foldAndToXor(BinaryOperator &I,
+                                 InstCombiner::BuilderTy &Builder) {
+  assert(I.getOpcode() == Instruction::And);
+  Value *Op0 = I.getOperand(0);
+  Value *Op1 = I.getOperand(1);
+  Value *A, *B;
+
+  // Operand complexity canonicalization guarantees that the 'or' is Op0.
+  // (A | B) & ~(A & B) --> A ^ B
+  // (A | B) & ~(B & A) --> A ^ B
+  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+      match(Op1, m_Not(m_c_And(m_Specific(A), m_Specific(B)))))
+    return BinaryOperator::CreateXor(A, B);
+
+  // (A | ~B) & (~A | B) --> ~(A ^ B)
+  // (A | ~B) & (B | ~A) --> ~(A ^ B)
+  // (~B | A) & (~A | B) --> ~(A ^ B)
+  // (~B | A) & (B | ~A) --> ~(A ^ B)
+  if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
+      match(Op1, m_c_Or(m_Not(m_Specific(A)), m_Value(B))))
+    return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
+
+  return nullptr;
+}
+
+static Instruction *foldOrToXor(BinaryOperator &I,
+                                InstCombiner::BuilderTy &Builder) {
+  assert(I.getOpcode() == Instruction::Or);
+  Value *Op0 = I.getOperand(0);
+  Value *Op1 = I.getOperand(1);
+  Value *A, *B;
+
+  // Operand complexity canonicalization guarantees that the 'and' is Op0.
+  // (A & B) | ~(A | B) --> ~(A ^ B)
+  // (A & B) | ~(B | A) --> ~(A ^ B)
+  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+      match(Op1, m_Not(m_c_Or(m_Specific(A), m_Specific(B)))))
+    return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
+
+  // (A & ~B) | (~A & B) --> A ^ B
+  // (A & ~B) | (B & ~A) --> A ^ B
+  // (~B & A) | (~A & B) --> A ^ B
+  // (~B & A) | (B & ~A) --> A ^ B
+  if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
+      match(Op1, m_c_And(m_Not(m_Specific(A)), m_Specific(B))))
+    return BinaryOperator::CreateXor(A, B);
+
+  return nullptr;
+}
+
 // FIXME: We use commutative matchers (m_c_*) for some, but not all, matches
 // here. We should standardize that construct where it is needed or choose some
 // other way to ensure that commutated variants of patterns are not missed.
@@ -1247,15 +1297,19 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
   if (Value *V = SimplifyAndInst(Op0, Op1, DL, &TLI, &DT, &AC))
     return replaceInstUsesWith(I, V);
 
-  // (A|B)&(A|C) -> A|(B&C) etc
-  if (Value *V = SimplifyUsingDistributiveLaws(I))
-    return replaceInstUsesWith(I, V);
-
   // See if we can simplify any instructions used by the instruction whose sole
   // purpose is to compute bits we don't care about.
   if (SimplifyDemandedInstructionBits(I))
     return &I;
 
+  // Do this before using distributive laws to catch simple and/or/not patterns.
+  if (Instruction *Xor = foldAndToXor(I, *Builder))
+    return Xor;
+
+  // (A|B)&(A|C) -> A|(B&C) etc
+  if (Value *V = SimplifyUsingDistributiveLaws(I))
+    return replaceInstUsesWith(I, V);
+
   if (Value *V = SimplifyBSwap(I))
     return replaceInstUsesWith(I, V);
 
@@ -1366,19 +1420,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
     return DeMorgan;
 
   {
-    Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
-    // (A|B) & ~(A&B) -> A^B
-    if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-        match(Op1, m_Not(m_And(m_Value(C), m_Value(D)))) &&
-        ((A == C && B == D) || (A == D && B == C)))
-      return BinaryOperator::CreateXor(A, B);
-
-    // ~(A&B) & (A|B) -> A^B
-    if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
-        match(Op0, m_Not(m_And(m_Value(C), m_Value(D)))) &&
-        ((A == C && B == D) || (A == D && B == C)))
-      return BinaryOperator::CreateXor(A, B);
-
+    Value *A = nullptr, *B = nullptr, *C = nullptr;
     // A&(A^B) => A & ~B
     {
       Value *tmpOp0 = Op0;
@@ -2037,15 +2079,19 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
   if (Value *V = SimplifyOrInst(Op0, Op1, DL, &TLI, &DT, &AC))
     return replaceInstUsesWith(I, V);
 
-  // (A&B)|(A&C) -> A&(B|C) etc
-  if (Value *V = SimplifyUsingDistributiveLaws(I))
-    return replaceInstUsesWith(I, V);
-
   // See if we can simplify any instructions used by the instruction whose sole
   // purpose is to compute bits we don't care about.
   if (SimplifyDemandedInstructionBits(I))
     return &I;
 
+  // Do this before using distributive laws to catch simple and/or/not patterns.
+  if (Instruction *Xor = foldOrToXor(I, *Builder))
+    return Xor;
+
+  // (A&B)|(A&C) -> A&(B|C) etc
+  if (Value *V = SimplifyUsingDistributiveLaws(I))
+    return replaceInstUsesWith(I, V);
+
   if (Value *V = SimplifyBSwap(I))
     return replaceInstUsesWith(I, V);
 
@@ -2182,23 +2228,6 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
         return replaceInstUsesWith(I, V);
     }
 
-    // ((A&~B)|(~A&B)) -> A^B
-    if ((match(C, m_Not(m_Specific(D))) &&
-         match(B, m_Not(m_Specific(A)))))
-      return BinaryOperator::CreateXor(A, D);
-    // ((~B&A)|(~A&B)) -> A^B
-    if ((match(A, m_Not(m_Specific(D))) &&
-         match(B, m_Not(m_Specific(C)))))
-      return BinaryOperator::CreateXor(C, D);
-    // ((A&~B)|(B&~A)) -> A^B
-    if ((match(C, m_Not(m_Specific(B))) &&
-         match(D, m_Not(m_Specific(A)))))
-      return BinaryOperator::CreateXor(A, B);
-    // ((~B&A)|(B&~A)) -> A^B
-    if ((match(A, m_Not(m_Specific(B))) &&
-         match(D, m_Not(m_Specific(C)))))
-      return BinaryOperator::CreateXor(C, B);
-
     // ((A|B)&1)|(B&-2) -> (A&1) | B
     if (match(A, m_Or(m_Value(V1), m_Specific(B))) ||
         match(A, m_Or(m_Specific(B), m_Value(V1)))) {