[InstCombine] Fold (~(a | b) & c) | ~(a | c) into ~((b & c) | a)

```
----------------------------------------
define i4 @src(i4 %a, i4 %b, i4 %c) {
  %or1 = or i4 %b, %a
  %not1 = xor i4 %or1, -1
  %or2 = or i4 %a, %c
  %not2 = xor i4 %or2, -1
  %and = and i4 %not2, %b
  %or3 = or i4 %and, %not1
  ret i4 %or3
}

define i4 @tgt(i4 %a, i4 %b, i4 %c) {
  %and = and i4 %c, %b
  %or = or i4 %and, %a
  %or3 = xor i4 %or, -1
  ret i4 %or3
}
Transformation seems to be correct!
```

Differential Revision: https://reviews.llvm.org/D112338

Author: rampitec

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -2818,6 +2818,20 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
     }
   }
 
+  // (~(A | B) & C) | ~(A | C) --> ~((B & C) | A)
+  // TODO: One use checks are conservative. We just need to check that a total
+  //       number of multiple used values does not exceed 3.
+  if (match(Op0, m_OneUse(m_c_And(m_OneUse(m_Not(m_Or(m_Value(A), m_Value(B)))),
+                                  m_Value(C))))) {
+    if (match(Op1, m_Not(m_c_Or(m_Specific(A), m_Specific(C)))))
+      return BinaryOperator::CreateNot(
+          Builder.CreateOr(Builder.CreateAnd(B, C), A));
+
+    if (match(Op1, m_Not(m_c_Or(m_Specific(B), m_Specific(C)))))
+      return BinaryOperator::CreateNot(
+          Builder.CreateOr(Builder.CreateAnd(A, C), B));
+  }
+
   if (Instruction *DeMorgan = matchDeMorgansLaws(I, Builder))
     return DeMorgan;
 

llvm/test/Transforms/InstCombine/and-xor-or.ll

@@ -1069,12 +1069,9 @@ define i32 @or_not_and_wrong_b(i32 %a, i32 %b, i32 %c, i32 %d) {
 
 define i32 @or_and_not_not(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %b, %a
@@ -1089,12 +1086,9 @@ define i32 @or_and_not_not(i32 %a, i32 %b, i32 %c) {
 define i32 @or_and_not_not_commute1(i32 %a, i32 %b0, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute1(
 ; CHECK-NEXT:    [[B:%.*]] = sdiv i32 42, [[B0:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[B]], [[NOT2]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[B]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %b = sdiv i32 42, %b0 ; thwart complexity-based canonicalization
@@ -1109,12 +1103,9 @@ define i32 @or_and_not_not_commute1(i32 %a, i32 %b0, i32 %c) {
 
 define i32 @or_and_not_not_commute2(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute2(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %b, %a
@@ -1128,12 +1119,9 @@ define i32 @or_and_not_not_commute2(i32 %a, i32 %b, i32 %c) {
 
 define i32 @or_and_not_not_commute3(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute3(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[C:%.*]], [[A]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %b, %a
@@ -1147,12 +1135,9 @@ define i32 @or_and_not_not_commute3(i32 %a, i32 %b, i32 %c) {
 
 define i32 @or_and_not_not_commute4(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute4(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %a, %b
@@ -1166,12 +1151,9 @@ define i32 @or_and_not_not_commute4(i32 %a, i32 %b, i32 %c) {
 
 define i32 @or_and_not_not_commute5(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute5(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %b, %a
@@ -1186,12 +1168,9 @@ define i32 @or_and_not_not_commute5(i32 %a, i32 %b, i32 %c) {
 define i32 @or_and_not_not_commute6(i32 %a, i32 %b0, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute6(
 ; CHECK-NEXT:    [[B:%.*]] = sdiv i32 42, [[B0:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[C:%.*]], [[A]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[B]], [[NOT2]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[B]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %b = sdiv i32 42, %b0 ; thwart complexity-based canonicalization
@@ -1206,12 +1185,9 @@ define i32 @or_and_not_not_commute6(i32 %a, i32 %b0, i32 %c) {
 
 define i32 @or_and_not_not_commute7(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute7(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[C:%.*]], [[A]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %a, %b
@@ -1227,10 +1203,9 @@ define i32 @or_and_not_not_extra_not_use1(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_extra_not_use1(
 ; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
 ; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    call void @use(i32 [[NOT1]])
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
@@ -1289,11 +1264,9 @@ define i32 @or_and_not_not_extra_and_use(i32 %a, i32 %b, i32 %c) {
 define i32 @or_and_not_not_extra_or_use1(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_extra_or_use1(
 ; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C:%.*]], [[B]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    call void @use(i32 [[OR1]])
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
@@ -1309,12 +1282,10 @@ define i32 @or_and_not_not_extra_or_use1(i32 %a, i32 %b, i32 %c) {
 
 define i32 @or_and_not_not_extra_or_use2(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_extra_or_use2(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C:%.*]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND]], [[NOT1]]
+; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[C]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i32 [[TMP1]], [[A]]
+; CHECK-NEXT:    [[OR3:%.*]] = xor i32 [[TMP2]], -1
 ; CHECK-NEXT:    call void @use(i32 [[OR2]])
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;