[Instcombine] Canonicalize ~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)

[bcl5980]

Summary

~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)
https://alive2.llvm.org/ce/z/JHN2p4

[spatel]

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

3484

I see that the first match is shared, but this function name and description are not accurate if we add the new fold inside here.

It would be better to create/rename this function as foldNotXor() that has the first match, then it calls or includes sinkNotIntoXor() and includes the new code.

[spatel]

Was there a problem with D139300? That is the same transform as this, but coded differently, right? I find that version easier to read even if it repeats the match for ~xor.

[bcl5980]

In D139299#3975362, @spatel wrote:

Was there a problem with D139300? That is the same transform as this, but coded differently, right? I find that version easier to read even if it repeats the match for ~xor.

The original idea is this patch do
~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)

D139300 do
~(A & B) ^ (A | ?) -> (A & B) | ~(A | ?)

Then I find this patch can cover D139300, so I abandon D139300.

[spatel]

LGTM

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

if (D->hasOneUse() && match(M, m_Constant(C))) {
     Value *NotC = Builder.CreateNot(C);
     Value *RHS = Builder.CreateAnd(B, NotC);
     return BinaryOperator::CreateOr(LHS, RHS);
   }
 
   return nullptr;
 }
 
+static bool hasCommonOperand(Value *A, Value *B, Value *C, Value *D) {
+  return A == C || A == D || B == C || B == D;
+}
+
 // Transform
 //   ~(x ^ y)
 // into:
 //   (~x) ^ y
 // or into
 //   x ^ (~y)
 static Instruction *sinkNotIntoXor(BinaryOperator &I,
                                    InstCombiner::BuilderTy &Builder) {
   Value *X, *Y;
   // FIXME: one-use check is not needed in general, but currently we are unable
   // to fold 'not' into 'icmp', if that 'icmp' has multiple uses. (D35182)
   if (!match(&I, m_Not(m_OneUse(m_Xor(m_Value(X), m_Value(Y))))))
     return nullptr;
 
   // We only want to do the transform if it is free to do.
   if (InstCombiner::isFreeToInvert(X, X->hasOneUse())) {
     // Ok, good.
   } else if (InstCombiner::isFreeToInvert(Y, Y->hasOneUse())) {
     std::swap(X, Y);
-  } else
+  } else {
+    Value *A, *B, *C, *D;
+    // Canonicalize ~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)
+    // 4 commuted variants
+    if (match(X, m_And(m_Value(A), m_Value(B))) &&
+        match(Y, m_Or(m_Value(C), m_Value(D))) &&
+        hasCommonOperand(A, B, C, D)) {
+      Value *NotY = Builder.CreateNot(Y);
+      return BinaryOperator::CreateOr(X, NotY);
+    };
+
+    // Canonicalize ~((A | ?) ^ (A & B)) -> (A & B) | ~(A | ?)
+    // 4 commuted variants
+    if (match(Y, m_And(m_Value(A), m_Value(B))) &&
+        match(X, m_Or(m_Value(C), m_Value(D))) &&
+        hasCommonOperand(A, B, C, D)) {
+      Value *NotX = Builder.CreateNot(X);
+      return BinaryOperator::CreateOr(Y, NotX);
+    };
+
     return nullptr;
+  }
 
   Value *NotX = Builder.CreateNot(X, X->getName() + ".not");
   return BinaryOperator::CreateXor(NotX, Y, I.getName() + ".demorgan");
 }
 
 /// Canonicalize a shifty way to code absolute value to the more common pattern
 /// that uses negation and select.
 static Instruction *canonicalizeAbs(BinaryOperator &Xor,

llvm/test/Transforms/InstCombine/xor2.ll

;
   %xor1 = xor i8 %B, %A
   %not = xor i8 %A, 33
   %xor2 = xor i8 %not, %B
   %and = and i8 %xor2, %xor1
   %res = mul i8 %and, %xor2 ; to increase the use count for the xor
   ret i8 %res
 }
 
-; TODO: Canonicalize ~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)
+; Canonicalize ~((A & B) ^ (A | ?)) -> (A & B) | ~(A | ?)
 
 define i3 @not_xor_to_or_not1(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @not_xor_to_or_not1(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[XOR]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[NOT:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[NOT]]
 ;
   %or = or i3 %b, %c
   %and = and i3 %a, %c
   %xor = xor i3 %and, %or
   %not = xor i3 %xor, -1
   ret i3 %not
 }
 
 define i3 @not_xor_to_or_not2(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @not_xor_to_or_not2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[C:%.*]], [[B:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[XOR]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[NOT:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[NOT]]
 ;
   %or = or i3 %c, %b
   %and = and i3 %a, %c
   %xor = xor i3 %and, %or
   %not = xor i3 %xor, -1
   ret i3 %not
 }
 
 define i3 @not_xor_to_or_not3(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @not_xor_to_or_not3(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[C:%.*]], [[B:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[C]], [[A:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[XOR]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[NOT:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[NOT]]
 ;
   %or = or i3 %c, %b
   %and = and i3 %c, %a
   %xor = xor i3 %and, %or
   %not = xor i3 %xor, -1
   ret i3 %not
 }
 
 define i3 @not_xor_to_or_not4(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @not_xor_to_or_not4(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[C]], [[A:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[XOR]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[NOT:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[NOT]]
 ;
   %or = or i3 %b, %c
   %and = and i3 %c, %a
   %xor = xor i3 %and, %or
   %not = xor i3 %xor, -1
   ret i3 %not
 }
 
 define <3 x i5> @not_xor_to_or_not_vector(<3 x i5> %a, <3 x i5> %b, <3 x i5> %c) {
 ; CHECK-LABEL: @not_xor_to_or_not_vector(
 ; CHECK-NEXT:    [[OR:%.*]] = or <3 x i5> [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and <3 x i5> [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <3 x i5> [[OR]], [[AND]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor <3 x i5> [[XOR]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[OR]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[NOT:%.*]] = or <3 x i5> [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret <3 x i5> [[NOT]]
 ;
   %or = or <3 x i5> %b, %c
   %and = and <3 x i5> %a, %c
   %xor = xor <3 x i5> %or, %and
   %not = xor <3 x i5> %xor, <i5 -1, i5 -1, i5 -1>
   ret <3 x i5> %not
 }
 
 define <3 x i5> @not_xor_to_or_not_vector_poison(<3 x i5> %a, <3 x i5> %b, <3 x i5> %c) {
 ; CHECK-LABEL: @not_xor_to_or_not_vector_poison(
 ; CHECK-NEXT:    [[OR:%.*]] = or <3 x i5> [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and <3 x i5> [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <3 x i5> [[OR]], [[AND]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor <3 x i5> [[XOR]], <i5 poison, i5 -1, i5 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[OR]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[NOT:%.*]] = or <3 x i5> [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret <3 x i5> [[NOT]]
 ;
   %or = or <3 x i5> %b, %c
   %and = and <3 x i5> %a, %c
   %xor = xor <3 x i5> %or, %and
   %not = xor <3 x i5> %xor, <i5 poison, i5 -1, i5 -1>
   ret <3 x i5> %not
 }
 
+; negative test : not one use
+
 define i3 @not_xor_to_or_not_2use(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @not_xor_to_or_not_2use(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[AND]], [[OR]]
 ; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[XOR]], -1
 ; CHECK-NEXT:    call void @use3(i3 [[XOR]])
 ; CHECK-NEXT:    ret i3 [[NOT]]
 ;
   %or = or i3 %b, %c
   %and = and i3 %a, %c
   %xor = xor i3 %and, %or
   %not = xor i3 %xor, -1
   call void @use3(i3 %xor)
   ret i3 %not
 }
 
-; TODO: Canonicalize ~(A & B) ^ (A | ?) -> (A & B) | ~(A | ?)
+; Canonicalize ~(A & B) ^ (A | ?) -> (A & B) | ~(A | ?)
 
 define i3 @xor_notand_to_or_not1(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not1(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[TMP1]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[XOR:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[XOR]]
 ;
   %or = or i3 %b, %c
   %and = and i3 %a, %c
   %not = xor i3 %and, -1
   %xor = xor i3 %not, %or
   ret i3 %xor
 }
 
 define i3 @xor_notand_to_or_not2(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[C:%.*]], [[B:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[TMP1]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[XOR:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[XOR]]
 ;
   %or = or i3 %c, %b
   %and = and i3 %a, %c
   %not = xor i3 %and, -1
   %xor = xor i3 %not, %or
   ret i3 %xor
 }
 
 define i3 @xor_notand_to_or_not3(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not3(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[C:%.*]], [[B:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[C]], [[A:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[TMP1]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[XOR:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[XOR]]
 ;
   %or = or i3 %c, %b
   %and = and i3 %c, %a
   %not = xor i3 %and, -1
   %xor = xor i3 %not, %or
   ret i3 %xor
 }
 
 define i3 @xor_notand_to_or_not4(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not4(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[C]], [[A:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[TMP1]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i3 [[OR]], -1
+; CHECK-NEXT:    [[XOR:%.*]] = or i3 [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret i3 [[XOR]]
 ;
   %or = or i3 %b, %c
   %and = and i3 %c, %a
   %not = xor i3 %and, -1
   %xor = xor i3 %not, %or
   ret i3 %xor
 }
 
 define <3 x i5> @xor_notand_to_or_not_vector(<3 x i5> %a, <3 x i5> %b, <3 x i5> %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not_vector(
 ; CHECK-NEXT:    [[OR:%.*]] = or <3 x i5> [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and <3 x i5> [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <3 x i5> [[TMP1]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[OR]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[XOR:%.*]] = or <3 x i5> [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret <3 x i5> [[XOR]]
 ;
   %or = or <3 x i5> %b, %c
   %and = and <3 x i5> %a, %c
   %not = xor <3 x i5> %and, <i5 -1, i5 -1, i5 -1>
   %xor = xor <3 x i5> %not, %or
   ret <3 x i5> %xor
 }
 
 define <3 x i5> @xor_notand_to_or_not_vector_poison(<3 x i5> %a, <3 x i5> %b, <3 x i5> %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not_vector_poison(
 ; CHECK-NEXT:    [[OR:%.*]] = or <3 x i5> [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and <3 x i5> [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[AND]], [[OR]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <3 x i5> [[TMP1]], <i5 -1, i5 poison, i5 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <3 x i5> [[OR]], <i5 -1, i5 -1, i5 -1>
+; CHECK-NEXT:    [[XOR:%.*]] = or <3 x i5> [[AND]], [[TMP1]]
 ; CHECK-NEXT:    ret <3 x i5> [[XOR]]
 ;
   %or = or <3 x i5> %b, %c
   %and = and <3 x i5> %a, %c
   %not = xor <3 x i5> %and, <i5 -1, i5 poison, i5 -1>
   %xor = xor <3 x i5> %not, %or
   ret <3 x i5> %xor
 }
 
+; negative test : not one use
+
 define i3 @xor_notand_to_or_not_2use(i3 %a, i3 %b, i3 %c) {
 ; CHECK-LABEL: @xor_notand_to_or_not_2use(
 ; CHECK-NEXT:    [[OR:%.*]] = or i3 [[B:%.*]], [[C:%.*]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i3 [[A:%.*]], [[C]]
 ; CHECK-NEXT:    [[NOT:%.*]] = xor i3 [[AND]], -1
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i3 [[OR]], [[NOT]]
 ; CHECK-NEXT:    call void @use3(i3 [[NOT]])
 ; CHECK-NEXT:    ret i3 [[XOR]]