Teach InstructionSimplify to fold (A & B) & A -> A & B and (A | B) | A -> A | B.

Reassociate does this but it doesn't catch all cases (e.g. if the operands are i1).

llvm-svn: 113651

llvm/lib/Analysis/InstructionSimplify.cpp

@@ -106,6 +106,16 @@ Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD) {
       (A == Op0 || B == Op0))
     return Op0;
   
+  // (A & B) & A -> A & B
+  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+      (A == Op1 || B == Op1))
+    return Op0;
+
+  // A & (A & B) -> A & B
+  if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
+      (A == Op0 || B == Op0))
+    return Op1;
+
   return 0;
 }
 
@@ -165,6 +175,16 @@ Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD) {
       (A == Op0 || B == Op0))
     return Op0;
   
+  // (A | B) | A -> A | B
+  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+      (A == Op1 || B == Op1))
+    return Op0;
+
+  // A | (A | B) -> A | B
+  if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
+      (A == Op0 || B == Op0))
+    return Op1;
+
   return 0;
 }
 

llvm/test/Transforms/InstCombine/and2.ll

@@ -8,3 +8,21 @@ define i1 @test1(double %X, double %Y) {
         ret i1 %bothcond
 ; CHECK:  fcmp ord double %Y, %X
 }
+
+define i1 @test2(i1 %X, i1 %Y) {
+  %a = and i1 %X, %Y
+  %b = and i1 %a, %X
+  ret i1 %b
+; CHECK: @test2
+; CHECK-NEXT: and i1 %X, %Y
+; CHECK-NEXT: ret
+}
+
+define i32 @test3(i32 %X, i32 %Y) {
+  %a = and i32 %X, %Y
+  %b = and i32 %Y, %a
+  ret i32 %b
+; CHECK: @test3
+; CHECK-NEXT: and i32 %X, %Y
+; CHECK-NEXT: ret
+}

llvm/test/Transforms/InstCombine/or.ll

@@ -350,3 +350,20 @@ define <4 x i32> @test32(<4 x i1> %and.i1352, <4 x i32> %vecinit6.i176, <4 x i32
 ; CHECK: or <4 x i32> %and.i, %and.i129
 }
 
+define i1 @test33(i1 %X, i1 %Y) {
+  %a = or i1 %X, %Y
+  %b = or i1 %a, %X
+  ret i1 %b
+; CHECK: @test33
+; CHECK-NEXT: or i1 %X, %Y
+; CHECK-NEXT: ret
+}
+
+define i32 @test34(i32 %X, i32 %Y) {
+  %a = or i32 %X, %Y
+  %b = or i32 %Y, %a
+  ret i32 %b
+; CHECK: @test34
+; CHECK-NEXT: or i32 %X, %Y
+; CHECK-NEXT: ret
+}