[llvm] b92412f - [InstCombine] Fold `(a & ~b) & ~c` to `a & ~(b | c)`

[Stanislav Mekhanoshin via llvm-commits]

Author: Stanislav Mekhanoshin
Date: 2021-10-20T13:05:46-07:00
New Revision: b92412fb286be26d6f033b9ec283b1b18cb57869

URL: https://github.com/llvm/llvm-project/commit/b92412fb286be26d6f033b9ec283b1b18cb57869
DIFF: https://github.com/llvm/llvm-project/commit/b92412fb286be26d6f033b9ec283b1b18cb57869.diff

LOG: [InstCombine] Fold `(a & ~b) & ~c` to `a & ~(b | c)`

  %not1 = xor i32 %b, -1
  %not2 = xor i32 %c, -1
  %and1 = and i32 %a, %not1
  %and2 = and i32 %and1, %not2
=>
  %i1 = or i32 %b, %c
  %i2 = xor i32 %1, -1
  %and2 = and i32 %i2, %a

Differential Revision: https://reviews.llvm.org/D112108

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 901b7cfbe060..df2595ad5849 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2012,6 +2012,13 @@ Instruction *InstCombinerImpl::visitAnd(BinaryOperator &I) {
     if (match(Op0, m_c_Xor(m_Not(m_Value(A)), m_Value(B))) &&
         match(Op1, m_c_Or(m_Specific(A), m_Specific(B))))
       return BinaryOperator::CreateAnd(A, B);
+
+    // (A & ~B) & ~C -> A & ~(B | C)
+    // (~B & A) & ~C -> A & ~(B | C)
+    if (match(Op0, m_OneUse(m_c_And(m_Value(A), m_Not(m_Value(B))))) &&
+        match(Op1, m_Not(m_Value(C))))
+      return BinaryOperator::CreateAnd(
+          A, Builder.CreateNot(Builder.CreateOr(B, C)));
   }
 
   {

diff  --git a/llvm/test/Transforms/InstCombine/and-xor-or.ll b/llvm/test/Transforms/InstCombine/and-xor-or.ll
index ec9f335a6c90..3d93faf2f9d6 100644
--- a/llvm/test/Transforms/InstCombine/and-xor-or.ll
+++ b/llvm/test/Transforms/InstCombine/and-xor-or.ll
@@ -522,10 +522,9 @@ define i64 @sext_or_chain_two_uses2(i64 %a, i16 %b, i16 %c, i64 %d) {
 define i32 @not_and_and_not(i32 %a0, i32 %b, i32 %c) {
 ; CHECK-LABEL: @not_and_and_not(
 ; CHECK-NEXT:    [[A:%.*]] = sdiv i32 42, [[A0:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[B:%.*]], -1
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[C:%.*]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[A]], [[NOT1]]
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[AND1]], [[NOT2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = or i32 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[A]], [[TMP2]]
 ; CHECK-NEXT:    ret i32 [[AND2]]
 ;
   %a = sdiv i32 42, %a0 ; thwart complexity-based canonicalization
@@ -539,10 +538,9 @@ define i32 @not_and_and_not(i32 %a0, i32 %b, i32 %c) {
 define <4 x i64> @not_and_and_not_4i64(<4 x i64> %a0, <4 x i64> %b, <4 x i64> %c) {
 ; CHECK-LABEL: @not_and_and_not_4i64(
 ; CHECK-NEXT:    [[A:%.*]] = sdiv <4 x i64> <i64 42, i64 42, i64 42, i64 42>, [[A0:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor <4 x i64> [[B:%.*]], <i64 -1, i64 -1, i64 -1, i64 -1>
-; CHECK-NEXT:    [[NOT2:%.*]] = xor <4 x i64> [[C:%.*]], <i64 -1, i64 -1, i64 -1, i64 -1>
-; CHECK-NEXT:    [[AND1:%.*]] = and <4 x i64> [[A]], [[NOT1]]
-; CHECK-NEXT:    [[AND2:%.*]] = and <4 x i64> [[AND1]], [[NOT2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = or <4 x i64> [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor <4 x i64> [[TMP1]], <i64 -1, i64 -1, i64 -1, i64 -1>
+; CHECK-NEXT:    [[AND2:%.*]] = and <4 x i64> [[A]], [[TMP2]]
 ; CHECK-NEXT:    ret <4 x i64> [[AND2]]
 ;
   %a = sdiv <4 x i64> <i64 42, i64 42, i64 42, i64 42>, %a0 ; thwart complexity-based canonicalization
@@ -557,10 +555,9 @@ define <4 x i64> @not_and_and_not_4i64(<4 x i64> %a0, <4 x i64> %b, <4 x i64> %c
 
 define i32 @not_and_and_not_commute1(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @not_and_and_not_commute1(
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[B:%.*]], -1
-; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[C:%.*]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOT1]], [[A:%.*]]
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[AND1]], [[NOT2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = or i32 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[TMP2]], [[A:%.*]]
 ; CHECK-NEXT:    ret i32 [[AND2]]
 ;
   %not1 = xor i32 %b, -1
@@ -576,10 +573,10 @@ declare void @use(i32)
 define i32 @not_and_and_not_commute2_extra_not_use(i32 %a0, i32 %b, i32 %c) {
 ; CHECK-LABEL: @not_and_and_not_commute2_extra_not_use(
 ; CHECK-NEXT:    [[A:%.*]] = sdiv i32 42, [[A0:%.*]]
-; CHECK-NEXT:    [[NOT1:%.*]] = xor i32 [[B:%.*]], -1
 ; CHECK-NEXT:    [[NOT2:%.*]] = xor i32 [[C:%.*]], -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[A]], [[NOT1]]
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[AND1]], [[NOT2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = or i32 [[B:%.*]], [[C]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[A]], [[TMP2]]
 ; CHECK-NEXT:    call void @use(i32 [[NOT2]])
 ; CHECK-NEXT:    ret i32 [[AND2]]
 ;