From b01865c210f4272904b3b3099474ee7f43bc7bec Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Sun, 30 Nov 2008 13:52:49 +0000
Subject: [PATCH] Add instruction combining for ((A&~B)|(~A&B)) -> A^B and all
 permutations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60291 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/README.txt                         |  6 ---
 .../Scalar/InstructionCombining.cpp           | 23 ++++++++++
 test/Transforms/InstCombine/or-to-xor.ll      | 42 +++++++++++++++++++
 3 files changed, 65 insertions(+), 6 deletions(-)
 create mode 100644 test/Transforms/InstCombine/or-to-xor.ll

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index bf7c0b14475..17b830d5d4a 100644
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -1171,12 +1171,6 @@ Should combine to "a | 1".  Currently not optimized with "clang
 
 //===---------------------------------------------------------------------===//
 
-int a(int a, int b, int c) {return ((a&~b) | (~a&b));}
-Should fold to xor.  Currently not optimized with "clang -emit-llvm-bc
-| opt -std-compile-opts".
-
-//===---------------------------------------------------------------------===//
-
 int a(int a, int b, int c) {return (~a & c) | ((c|a) & b);}
 Should fold to "(~a & c) | (a & b)".  Currently not optimized with
 "clang -emit-llvm-bc | opt -std-compile-opts".
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index ace3ff80d4f..c79bf9c7523 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4638,6 +4638,29 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
       return Match;
     if (Instruction *Match = MatchSelectFromAndOr(D, A, B, C))
       return Match;
+
+    V1 = V2 = 0;
+
+    // ((A&~B)|(~A&B)) -> A^B
+    if ((match(C, m_Not(m_Value(V1))) &&
+         match(B, m_Not(m_Value(V2)))))
+      if (V1 == D && V2 == A)
+        return BinaryOperator::CreateXor(V1, V2);
+    // ((~B&A)|(~A&B)) -> A^B
+    if ((match(A, m_Not(m_Value(V1))) &&
+         match(B, m_Not(m_Value(V2)))))
+      if (V1 == D && V2 == C)
+        return BinaryOperator::CreateXor(V1, V2);
+    // ((A&~B)|(B&~A)) -> A^B
+    if ((match(C, m_Not(m_Value(V1))) &&
+         match(D, m_Not(m_Value(V2)))))
+      if (V1 == B && V2 == A)
+        return BinaryOperator::CreateXor(V1, V2);
+    // ((~B&A)|(B&~A)) -> A^B
+    if ((match(A, m_Not(m_Value(V1))) &&
+         match(D, m_Not(m_Value(V2)))))
+      if (V1 == B && V2 == C)
+        return BinaryOperator::CreateXor(V1, V2);
   }
   
   // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
diff --git a/test/Transforms/InstCombine/or-to-xor.ll b/test/Transforms/InstCombine/or-to-xor.ll
new file mode 100644
index 00000000000..f403412bd5c
--- /dev/null
+++ b/test/Transforms/InstCombine/or-to-xor.ll
@@ -0,0 +1,42 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {xor i32 %b, %a} | count 4
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {and}
+
+define i32 @func1(i32 %a, i32 %b) nounwind readnone {
+entry:
+	%b_not = xor i32 %b, -1
+	%0 = and i32 %a, %b_not
+	%a_not = xor i32 %a, -1
+	%1 = and i32 %a_not, %b
+	%2 = or i32 %0, %1
+	ret i32 %2
+}
+
+define i32 @func2(i32 %a, i32 %b) nounwind readnone {
+entry:
+	%b_not = xor i32 %b, -1
+	%0 = and i32 %b_not, %a
+	%a_not = xor i32 %a, -1
+	%1 = and i32 %a_not, %b
+	%2 = or i32 %0, %1
+	ret i32 %2
+}
+
+define i32 @func3(i32 %a, i32 %b) nounwind readnone {
+entry:
+	%b_not = xor i32 %b, -1
+	%0 = and i32 %a, %b_not
+	%a_not = xor i32 %a, -1
+	%1 = and i32 %b, %a_not
+	%2 = or i32 %0, %1
+	ret i32 %2
+}
+
+define i32 @func4(i32 %a, i32 %b) nounwind readnone {
+entry:
+	%b_not = xor i32 %b, -1
+	%0 = and i32 %b_not, %a
+	%a_not = xor i32 %a, -1
+	%1 = and i32 %b, %a_not
+	%2 = or i32 %0, %1
+	ret i32 %2
+}