[PATCH] D112338: [InstCombine] Fold `(~(a | b) & c) | ~(a | c)` into `~((b & c) | a)`

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec created this revision.
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  ----------------------------------------
  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!


https://reviews.llvm.org/D112338

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
@@ -927,12 +927,9 @@
 
 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
@@ -946,12 +943,9 @@
 
 define i32 @or_and_not_not_commute1(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_and_not_not_commute1(
-; 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
@@ -965,12 +959,9 @@
 
 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
Index: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2796,6 +2796,18 @@
   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 & 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_Not(m_c_Or(m_Specific(A), m_Specific(C))))))
+      return BinaryOperator::CreateNot(
+          Builder.CreateOr(Builder.CreateAnd(B, C), A));
+
+    if (match(Op1, m_OneUse(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;
 


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