From 63cf26cf019ccffe107b78e57f2b1417ac7a8123 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 4 Sep 2018 23:22:13 +0000
Subject: [InstCombine] fix xor-or-xor fold to check uses and handle commutes

I'm probably missing some way to use m_Deferred to remove the code
duplication, but that can be a follow-up.

The improvement in demand_shrink_nsw.ll is an example of missing
the fold because the pattern matching was deficient. I didn't try
to follow the bits in that test, but Alive says it's correct:
https://rise4fun.com/Alive/ugc

llvm-svn: 341426
---
 .../Transforms/InstCombine/InstCombineAndOrXor.cpp | 53 +++++++++-------------
 1 file changed, 21 insertions(+), 32 deletions(-)

(limited to 'llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp')

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 202ec074e58..9e6f09dab3c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2791,41 +2791,30 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
       match(Op0, m_OneUse(m_c_And(m_Value(X), m_Specific(Op1)))))
     return BinaryOperator::CreateAnd(Op1, Builder.CreateNot(X));
 
-  {
-    Value *A, *B, *C, *D;
-    // (A ^ C)^(A | B) -> ((~A) & B) ^ C
-    if (match(Op0, m_Xor(m_Value(D), m_Value(C))) &&
-        match(Op1, m_Or(m_Value(A), m_Value(B)))) {
-      if (D == A)
-        return BinaryOperator::CreateXor(
-            Builder.CreateAnd(Builder.CreateNot(A), B), C);
-      if (D == B)
-        return BinaryOperator::CreateXor(
-            Builder.CreateAnd(Builder.CreateNot(B), A), C);
-    }
-    // (A | B)^(A ^ C) -> ((~A) & B) ^ C
-    if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-        match(Op1, m_Xor(m_Value(D), m_Value(C)))) {
-      if (D == A)
-        return BinaryOperator::CreateXor(
-            Builder.CreateAnd(Builder.CreateNot(A), B), C);
-      if (D == B)
-        return BinaryOperator::CreateXor(
-            Builder.CreateAnd(Builder.CreateNot(B), A), C);
-    }
-    // (A & B) ^ (A ^ B) -> (A | B)
-    if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
-        match(Op1, m_c_Xor(m_Specific(A), m_Specific(B))))
-      return BinaryOperator::CreateOr(A, B);
-    // (A ^ B) ^ (A & B) -> (A | B)
-    if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
-        match(Op1, m_c_And(m_Specific(A), m_Specific(B))))
-      return BinaryOperator::CreateOr(A, B);
-  }
+  Value *A, *B, *C;
+  // (A ^ B) ^ (A | C) --> (~A & C) ^ B -- There are 4 commuted variants.
+  if (match(&I, m_c_Xor(m_OneUse(m_Xor(m_Value(A), m_Value(B))),
+                        m_OneUse(m_c_Or(m_Deferred(A), m_Value(C))))))
+      return BinaryOperator::CreateXor(
+          Builder.CreateAnd(Builder.CreateNot(A), C), B);
+
+  // (A ^ B) ^ (B | C) --> (~B & C) ^ A -- There are 4 commuted variants.
+  if (match(&I, m_c_Xor(m_OneUse(m_Xor(m_Value(A), m_Value(B))),
+                        m_OneUse(m_c_Or(m_Deferred(B), m_Value(C))))))
+      return BinaryOperator::CreateXor(
+          Builder.CreateAnd(Builder.CreateNot(B), C), A);
+
+  // (A & B) ^ (A ^ B) -> (A | B)
+  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+      match(Op1, m_c_Xor(m_Specific(A), m_Specific(B))))
+    return BinaryOperator::CreateOr(A, B);
+  // (A ^ B) ^ (A & B) -> (A | B)
+  if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
+      match(Op1, m_c_And(m_Specific(A), m_Specific(B))))
+    return BinaryOperator::CreateOr(A, B);
 
   // (A & ~B) ^ ~A -> ~(A & B)
   // (~B & A) ^ ~A -> ~(A & B)
-  Value *A, *B;
   if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
       match(Op1, m_Not(m_Specific(A))))
     return BinaryOperator::CreateNot(Builder.CreateAnd(A, B));
-- 
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