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

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

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D113861

2 files changed, 43 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d406583..864eeea 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2265,6 +2265,19 @@ static Value *SimplifyOrInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
        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
diff --git a/llvm/test/Transforms/InstSimplify/or.ll b/llvm/test/Transforms/InstSimplify/or.ll
index 038112a..d11aedf 100644
--- a/llvm/test/Transforms/InstSimplify/or.ll
+++ b/llvm/test/Transforms/InstSimplify/or.ll
@@ -451,9 +451,7 @@ define i32 @and_or_not_or8(i32 %A, i32 %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
@@ -461,12 +459,25 @@ define i69 @or_or_xor(i69 %A, i69 %B) {
   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
@@ -474,6 +485,19 @@ define <4 x i4> @or_or_xor_commuted(<4 x i4> %A, <4 x i4> %B) {
   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