[InstSimplify] Fold A|B | (A^B) --> A|B

[MehrHeidar]

Summary

This patch adds the following fold opportunity:
A|B | (A^B) --> A|B

that is reported here : https://bugs.llvm.org/show_bug.cgi?id=52479

https://alive2.llvm.org/ce/z/33-My-

Test cases with base results are added in D113860

Previously authored in D113861, but due to committing with not giving the credits has been reverted.

[MehrHeidar]

This comment was removed by MehrHeidar.

[aaronpuchert]

No need to open another revision, D113861 has already been reopened.

llvm/lib/Analysis/InstructionSimplify.cpp

static Value *SimplifyOrInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
   // (~A ^ B) | (B & A) -> (~A ^ B)
   // (B ^ ~A) | (A & B) -> (B ^ ~A)
   // (B ^ ~A) | (B & A) -> (B ^ ~A)
   if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
       (match(Op0, m_c_Xor(m_Specific(A), m_Not(m_Specific(B)))) ||
        match(Op0, m_c_Xor(m_Not(m_Specific(A)), m_Specific(B)))))
     return Op0;
 
+  // (A | B) | (A ^ B) --> A | B
+  // (B | A) | (A ^ B) --> B | A
+  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
+      match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
+    return Op0;
+
+  // Commute the outer 'or' operands.
+  // (A ^ B) | (A | B) --> A | B
+  // (A ^ B) | (B | A) --> B | A
+  if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
+      match(Op1, m_c_Or(m_Specific(A), m_Specific(B))))
+    return Op1;
+
   // (~A & B) | ~(A | B) --> ~A
   // (~A & B) | ~(B | A) --> ~A
   // (B & ~A) | ~(A | B) --> ~A
   // (B & ~A) | ~(B | A) --> ~A
   if (match(Op0, m_c_And(m_CombineAnd(m_Value(NotA), m_Not(m_Value(A))),
                          m_Value(B))) &&
       match(Op1, m_Not(m_c_Or(m_Specific(A), m_Specific(B)))))
     return NotA;

llvm/test/Transforms/InstSimplify/or.ll

;
   ret i32 %i5
 }
 
 ; (A | B) | (A ^ B) --> A | B
 
 define i69 @or_or_xor(i69 %A, i69 %B) {
 ; CHECK-LABEL: @or_or_xor(
 ; CHECK-NEXT:    [[I1:%.*]] = or i69 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[I2:%.*]] = xor i69 [[A]], [[B]]
-; CHECK-NEXT:    [[I3:%.*]] = or i69 [[I1]], [[I2]]
-; CHECK-NEXT:    ret i69 [[I3]]
+; CHECK-NEXT:    ret i69 [[I1]]
 ;
   %i1 = or i69 %A, %B
   %i2 = xor i69 %A, %B
   %i3 = or i69 %i1, %i2
   ret i69 %i3
 }
 
+; (B | A) | (A ^ B) --> B | A
+
+define i8 @or_or_xor_inner_or_commuted(i8 %A, i8 %B) {
+; CHECK-LABEL: @or_or_xor_inner_or_commuted(
+; CHECK-NEXT:    [[I1:%.*]] = or i8 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    ret i8 [[I1]]
+;
+  %i1 = or i8 %B, %A
+  %i2 = xor i8 %A, %B
+  %i3 = or i8 %i1, %i2
+  ret i8 %i3
+}
+
+; (A ^ B) | (A | B) --> A | B
+
 define <4 x i4> @or_or_xor_commuted(<4 x i4> %A, <4 x i4> %B) {
 ; CHECK-LABEL: @or_or_xor_commuted(
 ; CHECK-NEXT:    [[I1:%.*]] = or <4 x i4> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[I2:%.*]] = xor <4 x i4> [[A]], [[B]]
-; CHECK-NEXT:    [[I3:%.*]] = or <4 x i4> [[I2]], [[I1]]
-; CHECK-NEXT:    ret <4 x i4> [[I3]]
+; CHECK-NEXT:    ret <4 x i4> [[I1]]
 ;
   %i1 = or <4 x i4> %A, %B
   %i2 = xor <4 x i4> %A, %B
   %i3 = or <4 x i4> %i2, %i1
   ret <4 x i4> %i3
 }
 
+; (A ^ B) | (B | A) --> B | A
+
+define i4 @or_or_xor_inner_or_outer_or_commuted(i4 %A, i4 %B) {
+; CHECK-LABEL: @or_or_xor_inner_or_outer_or_commuted(
+; CHECK-NEXT:    [[I1:%.*]] = or i4 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    ret i4 [[I1]]
+;
+  %i1 = or i4 %B, %A
+  %i2 = xor i4 %A, %B
+  %i3 = or i4 %i2, %i1
+  ret i4 %i3
+}
+
 define i32 @shifted_all_ones(i32 %shamt) {
 ; CHECK-LABEL: @shifted_all_ones(
 ; CHECK-NEXT:    ret i32 -1
 ;
   %r = lshr i32 -1, %shamt
   %s = sub i32 32, %shamt
   %l = shl i32 -1, %s
   %o = or i32 %r, %l