[PATCH] D112276: [InstCombine] Fold `(c & ~(a | b)) | (b & ~(a | c))` to `~a & (b ^ c)`

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec created this revision.
rampitec added a reviewer: spatel.
Herald added a subscriber: hiraditya.
rampitec requested review of this revision.
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  ----------------------------------------
  define i4 @src(i4 %a, i4 %b, i4 %c) {
  %0:
    %or1 = or i4 %a, %b
    %not1 = xor i4 %or1, 15
    %and1 = and i4 %not1, %c
    %or2 = or i4 %a, %c
    %not2 = xor i4 %or2, 15
    %and2 = and i4 %not2, %b
    %or3 = or i4 %and1, %and2
    ret i4 %or3
  }
  =>
  define i4 @tgt(i4 %a, i4 %b, i4 %c) {
  %0:
    %xor = xor i4 %b, %c
    %not = xor i4 %a, 15
    %or3 = and i4 %xor, %not
    ret i4 %or3
  }
  Transformation seems to be correct!


https://reviews.llvm.org/D112276

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/and-xor-or.ll


Index: llvm/test/Transforms/InstCombine/and-xor-or.ll
===================================================================
--- llvm/test/Transforms/InstCombine/and-xor-or.ll
+++ llvm/test/Transforms/InstCombine/and-xor-or.ll
@@ -703,13 +703,9 @@
 
 define i32 @or_not_and(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_not_and(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOT1]], [[C:%.*]]
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[A:%.*]], -1
+; CHECK-NEXT:    [[OR3:%.*]] = and i32 [[TMP1]], [[TMP2]]
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %a, %b
@@ -725,13 +721,9 @@
 define i32 @or_not_and_commute1(i32 %a, i32 %b0, i32 %c) {
 ; CHECK-LABEL: @or_not_and_commute1(
 ; CHECK-NEXT:    [[B:%.*]] = sdiv i32 42, [[B0:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOT1]], [[C:%.*]]
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[B]], [[NOT2]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[A:%.*]], -1
+; CHECK-NEXT:    [[OR3:%.*]] = and i32 [[TMP1]], [[TMP2]]
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %b = sdiv i32 42, %b0 ; thwart complexity-based canonicalization
@@ -748,13 +740,9 @@
 define i32 @or_not_and_commute2(i32 %a, i32 %b0, i32 %c) {
 ; CHECK-LABEL: @or_not_and_commute2(
 ; CHECK-NEXT:    [[B:%.*]] = sdiv i32 42, [[B0:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOT1]], [[C:%.*]]
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[C]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[B]], [[NOT2]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND2]], [[AND1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[A:%.*]], -1
+; CHECK-NEXT:    [[OR3:%.*]] = and i32 [[TMP1]], [[TMP2]]
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %b = sdiv i32 42, %b0 ; thwart complexity-based canonicalization
@@ -770,13 +758,9 @@
 
 define i32 @or_not_and_commute3(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_not_and_commute3(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[OR1]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOT1]], [[C:%.*]]
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[C]], [[A]]
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[OR2]], -1
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[NOT2]], [[B]]
-; CHECK-NEXT:    [[OR3:%.*]] = or i32 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[A:%.*]], -1
+; CHECK-NEXT:    [[OR3:%.*]] = and i32 [[TMP1]], [[TMP2]]
 ; CHECK-NEXT:    ret i32 [[OR3]]
 ;
   %or1 = or i32 %b, %a
Index: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2796,6 +2796,22 @@
   if (match(Op0, m_And(m_Or(m_Specific(Op1), m_Value(C)), m_Value(A))))
     return BinaryOperator::CreateOr(Op1, Builder.CreateAnd(A, C));
 
+  // (~(A | B) & C) | (~(A | C) & B) --> (B ^ C) & ~A
+  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_OneUse(m_c_And(
+                       m_OneUse(m_Not(m_c_Or(m_Specific(A), m_Specific(C)))),
+                       m_Specific(B)))))
+      return BinaryOperator::CreateAnd(Builder.CreateXor(B, C),
+                                       Builder.CreateNot(A));
+
+    if (match(Op1, m_OneUse(m_c_And(
+                       m_OneUse(m_Not(m_c_Or(m_Specific(B), m_Specific(C)))),
+                       m_Specific(A)))))
+      return BinaryOperator::CreateAnd(Builder.CreateXor(A, C),
+                                       Builder.CreateNot(B));
+  }
+
   if (Instruction *DeMorgan = matchDeMorgansLaws(I, Builder))
     return DeMorgan;
 


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