From: Sanjay Patel <spatel@rotateright.com>
Date: Sun, 23 Apr 2017 16:03:00 +0000 (+0000)
Subject: [InstCombine] add pattern matches for commuted variants of xor-to-xor
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1261555bf51ed904e7930cb47a8f0e14c5d1da77;p=llvm

[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 f320f125bf6..17a6fb9a402 100644
--- 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 48ae620138d..2f7afdfcbcc 100644
--- 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