[llvm] [InstCombine] Loosen one-use restriction if common operand is constant (PR #79767)

[via llvm-commits]

https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/79767

>From 45c52c0d54a35827684c30dfd0132598df87e6ff Mon Sep 17 00:00:00 2001
From: Rose <83477269+AtariDreams at users.noreply.github.com>
Date: Sun, 28 Jan 2024 15:32:44 -0500
Subject: [PATCH 1/2] [InstCombine] pre-commit tests (NFC)

---
 llvm/test/Transforms/InstCombine/xor-and-or.ll | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/llvm/test/Transforms/InstCombine/xor-and-or.ll b/llvm/test/Transforms/InstCombine/xor-and-or.ll
index feba47912b1da..c6efab205a157 100644
--- a/llvm/test/Transforms/InstCombine/xor-and-or.ll
+++ b/llvm/test/Transforms/InstCombine/xor-and-or.ll
@@ -241,4 +241,15 @@ define i1 @xor_and_or_negative_oneuse(i1 %c, i1 %x, i1 %y) {
   ret i1 %r
 }
 
+define i32 @xor_and_or_constant(i32 %B, i32 %C, i32 %D, i32 %E) {
+  %1 = or i32 42, %B
+  %2 = or i32 42, %C
+  %3 = xor i32 %1, %2
+  %4 = add i32 42, %D
+  %5 = mul i32 42, %E
+  %6 = add i32 %3, %4, %5
+  ret i32 %6
+}
+
 declare void @use(i1)
+declare i32 @use2(i32, i32)

>From e3ec1eca944edbdcc4a94e70d9e1995a74ee1a73 Mon Sep 17 00:00:00 2001
From: Rose <83477269+AtariDreams at users.noreply.github.com>
Date: Sun, 28 Jan 2024 13:30:29 -0500
Subject: [PATCH 2/2] [InstCombine] Loosen one-use restriction if common
 operand is constant

Add a new version that checks if A is a constant instead of one-use.
---
 .../Transforms/InstCombine/InstCombineAndOrXor.cpp    | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 6a827e2f3a963..9436329e87dee 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -4837,7 +4837,6 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
     return BinaryOperator::CreateNot(Builder.CreateAnd(Op0, B));
 
   // (A | B) ^ (A | C) --> (B ^ C) & ~A -- There are 4 commuted variants.
-  // TODO: Loosen one-use restriction if common operand is a constant.
   Value *D;
   if (match(Op0, m_OneUse(m_Or(m_Value(A), m_Value(B)))) &&
       match(Op1, m_OneUse(m_Or(m_Value(C), m_Value(D))))) {
@@ -4851,6 +4850,16 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
     }
   }
 
+  // (A | B) ^ (A | C) --> (B ^ C) & ~A -- There are 4 commuted variants.
+  // We do this if common operand is a constant.
+  if (match(Op0, m_c_Or(m_Value(A), m_Value(B))) &&
+      match(Op1, m_c_Or(m_Specific(A), m_Value(C)))) {
+    if (match(A, m_ImmConstant())) {
+      Value *NotA = Builder.CreateNot(A);
+      return BinaryOperator::CreateAnd(Builder.CreateXor(B, C), NotA);
+    }
+  }
+
   // (A & B) ^ (A | C) --> A ? ~B : C -- There are 4 commuted variants.
   if (I.getType()->isIntOrIntVectorTy(1) &&
       match(Op0, m_OneUse(m_LogicalAnd(m_Value(A), m_Value(B)))) &&