[InstCombine] Fold sub (and A, B) (or A, B)) to neg (xor A, B)

Summary:
```
Name: sub(and(x, y), or(x, y)) -> neg(xor(x, y))
%or = or i32 %y, %x
%and = and i32 %x, %y
%sub = sub i32 %and, %or
  =>
%sub1 = xor i32 %x, %y
%sub = sub i32 0, %sub1

Optimization: sub(and(x, y), or(x, y)) -> neg(xor(x, y))
Done: 1
Optimization is correct!
```

https://rise4fun.com/Alive/VI6

Found by @lebedev.ri. Also author of the proof.

Reviewers: lebedev.ri, spatel

Reviewed By: lebedev.ri

Subscribers: llvm-commits, lebedev.ri

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67155

llvm-svn: 370934

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 776bef3..fbd0165 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1725,6 +1725,15 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
       return BinaryOperator::CreateXor(A, B);
   }
 
+  // (sub (and A, B) (or A, B)) --> neg (xor A, B)
+  {
+    Value *A, *B;
+    if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+        match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
+        (Op0->hasOneUse() || Op1->hasOneUse()))
+      return BinaryOperator::CreateNeg(Builder.CreateXor(A, B));
+  }
+
   // (sub (or A, B), (xor A, B)) --> (and A, B)
   {
     Value *A, *B;

diff --git a/llvm/test/Transforms/InstCombine/sub-and-or-not-xor.ll b/llvm/test/Transforms/InstCombine/sub-and-or-not-xor.ll
index dc56ba7..980433e 100644 (file)
--- a/llvm/test/Transforms/InstCombine/sub-and-or-not-xor.ll
+++ b/llvm/test/Transforms/InstCombine/sub-and-or-not-xor.ll
@@ -5,9 +5,8 @@ declare void @use(i32)
 
 define i32 @sub_to_xor(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
   %or = or i32 %x, %y
@@ -18,9 +17,8 @@ define i32 @sub_to_xor(i32 %x, i32 %y) {
 
 define i32 @sub_to_xor_extra_use_sub(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor_extra_use_sub(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    call void @use(i32 [[SUB]])
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
@@ -33,10 +31,10 @@ define i32 @sub_to_xor_extra_use_sub(i32 %x, i32 %y) {
 
 define i32 @sub_to_xor_extra_use_and(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor_extra_use_and(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    call void @use(i32 [[AND]])
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
   %or = or i32 %x, %y
@@ -50,8 +48,8 @@ define i32 @sub_to_xor_extra_use_or(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor_extra_use_or(
 ; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    call void @use(i32 [[OR]])
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
   %or = or i32 %x, %y
@@ -63,9 +61,8 @@ define i32 @sub_to_xor_extra_use_or(i32 %x, i32 %y) {
 
 define i32 @sub_to_xor_or_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor_or_commuted(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[Y:%.*]], [[X:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
   %or = or i32 %y, %x
@@ -76,9 +73,8 @@ define i32 @sub_to_xor_or_commuted(i32 %x, i32 %y) {
 
 define i32 @sub_to_xor_and_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sub_to_xor_and_commuted(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[Y]], [[X]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SUB]]
 ;
   %or = or i32 %x, %y
@@ -89,9 +85,8 @@ define i32 @sub_to_xor_and_commuted(i32 %x, i32 %y) {
 
 define <2 x i32> @sub_to_xor_vec(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @sub_to_xor_vec(
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i32> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i32> [[Y]], [[X]]
-; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i32> [[AND]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <2 x i32> [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i32> zeroinitializer, [[TMP1]]
 ; CHECK-NEXT:    ret <2 x i32> [[SUB]]
 ;
   %or = or <2 x i32> %x, %y