[InstCombine] add pattern matches for commuted variants of xor-to-xor

There's probably some better way to write this that eliminates the
code duplication without hurting readability, but at least this
eliminates the logic holes and is hopefully slightly more efficient
than creating new instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301129 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index f320f125bf6bfcc6b6f2017419d87098a6f07291..17a6fb9a40223273aaad23690c4110d0737b88a2 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2374,6 +2374,58 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
   return Changed ? &I : nullptr;
 }
 
+/// A ^ B can be specified using other logic ops in a variety of patterns. We
+/// can fold these early and efficiently by morphing an existing instruction.
+static Instruction *foldXorToXor(BinaryOperator &I) {
+  assert(I.getOpcode() == Instruction::Xor);
+  Value *Op0 = I.getOperand(0);
+  Value *Op1 = I.getOperand(1);
+  Value *A, *B;
+
+  // There are 4 commuted variants for each of the basic patterns.
+
+  // (A & B) ^ (A | B) -> A ^ B
+  // (A & B) ^ (B | A) -> A ^ B
+  // (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_c_Or(m_Specific(A), m_Specific(B)))) ||
+      (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+       match(Op1, m_c_And(m_Specific(A), m_Specific(B))))) {
+    I.setOperand(0, A);
+    I.setOperand(1, B);
+    return &I;
+  }
+
+  // (A | ~B) ^ (~A | B) -> A ^ B
+  // (~B | A) ^ (~A | B) -> A ^ B
+  // (~A | B) ^ (A | ~B) -> A ^ B
+  // (B | ~A) ^ (A | ~B) -> A ^ B
+  if ((match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
+       match(Op1, m_Or(m_Not(m_Specific(A)), m_Specific(B)))) ||
+      (match(Op0, m_c_Or(m_Not(m_Value(A)), m_Value(B))) &&
+       match(Op1, m_Or(m_Specific(A), m_Not(m_Specific(B)))))) {
+    I.setOperand(0, A);
+    I.setOperand(1, B);
+    return &I;
+  }
+
+  // (A & ~B) ^ (~A & B) -> A ^ B
+  // (~B & A) ^ (~A & B) -> A ^ B
+  // (~A & B) ^ (A & ~B) -> A ^ B
+  // (B & ~A) ^ (A & ~B) -> A ^ B
+  if ((match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
+       match(Op1, m_And(m_Not(m_Specific(A)), m_Specific(B)))) ||
+      (match(Op0, m_c_And(m_Not(m_Value(A)), m_Value(B))) &&
+       match(Op1, m_And(m_Specific(A), m_Not(m_Specific(B)))))) {
+    I.setOperand(0, A);
+    I.setOperand(1, B);
+    return &I;
+  }
+
+  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.
@@ -2387,6 +2439,9 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
   if (Value *V = SimplifyXorInst(Op0, Op1, DL, &TLI, &DT, &AC))
     return replaceInstUsesWith(I, V);
 
+  if (Instruction *NewXor = foldXorToXor(I))
+    return NewXor;
+
   // (A&B)^(A&C) -> A&(B^C) etc
   if (Value *V = SimplifyUsingDistributiveLaws(I))
     return replaceInstUsesWith(I, V);
@@ -2569,40 +2624,6 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
 
   {
     Value *A, *B, *C, *D;
-    // (A & B)^(A | B) -> A ^ B
-    if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
-        match(Op1, m_Or(m_Value(C), m_Value(D)))) {
-      if ((A == C && B == D) || (A == D && B == C))
-        return BinaryOperator::CreateXor(A, B);
-    }
-    // (A | B)^(A & B) -> A ^ B
-    if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-        match(Op1, m_And(m_Value(C), m_Value(D)))) {
-      if ((A == C && B == D) || (A == D && B == C))
-        return BinaryOperator::CreateXor(A, B);
-    }
-    // (A | ~B) ^ (~A | B) -> A ^ B
-    // (~B | A) ^ (~A | B) -> A ^ B
-    if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
-        match(Op1, m_Or(m_Not(m_Specific(A)), m_Specific(B))))
-      return BinaryOperator::CreateXor(A, B);
-
-    // (~A | B) ^ (A | ~B) -> A ^ B
-    if (match(Op0, m_Or(m_Not(m_Value(A)), m_Value(B))) &&
-        match(Op1, m_Or(m_Specific(A), m_Not(m_Specific(B))))) {
-      return BinaryOperator::CreateXor(A, B);
-    }
-    // (A & ~B) ^ (~A & B) -> A ^ B
-    // (~B & A) ^ (~A & B) -> A ^ B
-    if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
-        match(Op1, m_And(m_Not(m_Specific(A)), m_Specific(B))))
-      return BinaryOperator::CreateXor(A, B);
-
-    // (~A & B) ^ (A & ~B) -> A ^ B
-    if (match(Op0, m_And(m_Not(m_Value(A)), m_Value(B))) &&
-        match(Op1, m_And(m_Specific(A), m_Not(m_Specific(B))))) {
-      return BinaryOperator::CreateXor(A, B);
-    }
     // (A ^ C)^(A | B) -> ((~A) & B) ^ C
     if (match(Op0, m_Xor(m_Value(D), m_Value(C))) &&
         match(Op1, m_Or(m_Value(A), m_Value(B)))) {

diff --git a/test/Transforms/InstCombine/and-or-not.ll b/test/Transforms/InstCombine/and-or-not.ll
index 48ae620138d463eb43ba0de77f1dfda48bf8c69e..2f7afdfcbcccfbc4afbc409960d8a9fa6c465b90 100644 (file)
--- a/test/Transforms/InstCombine/and-or-not.ll
+++ b/test/Transforms/InstCombine/and-or-not.ll
@@ -124,7 +124,7 @@ define i32 @xor_to_xor4(i32 %a, i32 %b) {
 
 ; (a | ~b) ^ (~a | b) --> a ^ b
 
-; In the next 8 tests, cast instructions are used to thwart operand complexity 
+; In the next 8 tests, cast instructions are used to thwart operand complexity
 ; canonicalizations, so we can test all of the commuted patterns.
 
 define i32 @xor_to_xor5(float %fa, float %fb) {
@@ -150,11 +150,7 @@ define i32 @xor_to_xor6(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor6(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float %fa to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float %fb to i32
-; CHECK-NEXT:    [[NOTA:%.*]] = xor i32 [[A]], -1
-; CHECK-NEXT:    [[NOTB:%.*]] = xor i32 [[B]], -1
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A]], [[NOTB]]
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[B]], [[NOTA]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -230,11 +226,7 @@ define i32 @xor_to_xor10(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor10(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float %fa to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float %fb to i32
-; CHECK-NEXT:    [[NOTA:%.*]] = xor i32 [[A]], -1
-; CHECK-NEXT:    [[NOTB:%.*]] = xor i32 [[B]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[A]], [[NOTB]]
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[B]], [[NOTA]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32