[InstCombine] Keep the disjoint flag when combining two ORs if possible.

or-disjoint (or-disjoint X, C), V
-->
or-disjoint (or-disjoint X, V), C

or-disjoint (or X, C), V
-->
or (or-disjoint X, V), C

Proof: https://alive2.llvm.org/ce/z/wtTm5V
https://alive2.llvm.org/ce/z/WC7Ai2

Signed-off-by: feng.feng <[email protected]>

Author: fengfeng09

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -3894,12 +3894,23 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
   // be simplified by a later pass either, so we try swapping the inner/outer
   // ORs in the hopes that we'll be able to simplify it this way.
   // (X|C) | V --> (X|V) | C
+  // Pass the disjoint flag in the following two patterns:
+  // 1. or-disjoint (or-disjoint X, C), V -->
+  //    or-disjoint (or-disjoint X, V), C
+  //
+  // 2. or-disjoint (or X, C), V -->
+  //    or (or-disjoint X, V), C
   ConstantInt *CI;
   if (Op0->hasOneUse() && !match(Op1, m_ConstantInt()) &&
       match(Op0, m_Or(m_Value(A), m_ConstantInt(CI)))) {
+    bool IsDisjointOuter = cast<PossiblyDisjointInst>(I).isDisjoint();
+    bool IsDisjointInner = cast<PossiblyDisjointInst>(Op0)->isDisjoint();
     Value *Inner = Builder.CreateOr(A, Op1);
+    cast<PossiblyDisjointInst>(Inner)->setIsDisjoint(IsDisjointOuter);
     Inner->takeName(Op0);
-    return BinaryOperator::CreateOr(Inner, CI);
+    return IsDisjointOuter && IsDisjointInner
+               ? BinaryOperator::CreateDisjointOr(Inner, CI)
+               : BinaryOperator::CreateOr(Inner, CI);
   }
 
   // Change (or (bool?A:B),(bool?C:D)) --> (bool?(or A,C):(or B,D))

llvm/test/Transforms/InstCombine/or-or-combine.ll

@@ -5,8 +5,8 @@
 
 define i32 @test1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test1(
-; CHECK-NEXT:    [[INNER:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[OUTER:%.*]] = or i32 [[INNER]], 5
+; CHECK-NEXT:    [[INNER:%.*]] = or disjoint i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[OUTER:%.*]] = or disjoint i32 [[INNER]], 5
 ; CHECK-NEXT:    ret i32 [[OUTER]]
 ;
   %inner = or disjoint i32 %x, 5
@@ -16,7 +16,7 @@ define i32 @test1(i32 %x, i32 %y) {
 
 define i32 @test2(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test2(
-; CHECK-NEXT:    [[INNER:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[INNER:%.*]] = or disjoint i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    [[OUTER:%.*]] = or i32 [[INNER]], 5
 ; CHECK-NEXT:    ret i32 [[OUTER]]
 ;